Publications

Preprints

1. Species interactions drive continuous assembly of freshwater communities in stochastic environments
2023 – bioRxiv
Andrea Tabi, Tadeu Siqueira, Jonathan D. Tonkin

Understanding the factors driving the maintenance of long-term biodiversity in changing environments is essential for improving restoration and sustainability strategies in the face of global environmental change. Biodiversity is shaped by both niche and stochastic processes, however the strength of deterministic processes in unpredictable environmental regimes is highly debated. Since communities continuously change over time and space — species persist, disappear or (re)appear — understanding the drivers of species gains and losses from communities should inform us about whether niche or stochastic processes dominate community dynamics. Applying a nonparametric causal discovery approach to a 30-year time series containing annual abundances of benthic invertebrates across 66 locations in New Zealand rivers, we found a strong asynchronous causal relationship between species gains and losses directly driven by predation indicating that niche processes dominate community dynamics. Despite the unpredictable nature of these system, environmental noise was only indirectly related to species gains and losses through altering life history trait distribution. Using a stochastic birth-death framework, we demonstrate that the negative relationship between species gains and losses can not emerge without strong niche processes. Our results showed that even in systems that are dominated by unpredictable environmental variability, species interactions drive continuous community assembly.

Book chapters

2. Multiscale ecological resilience in braided rivers
2024 – Resilience and Riverine Landscapes
Holly A. L. Harris, Jonathan D. Tonkin, Angus R. McIntosh

Natural river systems are environmentally complex with dynamic flows; yet are capable of producing persistent ecological properties. This biocomplexity facilitates an array of resilience mechanisms that are potentially threatened by reductions in complexity through press disturbances. Using braided rivers as a model river ecosystem, we review key mechanisms of resilience in river systems driven by spatiotemporal heterogeneity. These mechanisms include shifting mosaics of habitats and asynchronous hydrological disturbances, and multiscale resilience through species traits and spatial movement and connectivity. We argue that understanding these mechanisms in braided rivers offers the potential for gaining insight into requirements for resilience in riverine ecosystems. Finally, biophysical feedback loops in braided rivers can drive the system from a highly complex environment to single-channel systems, which are vulnerable to flood disturbances and increase the potential for the loss of key ecosystem properties.

1. Climate change and extreme events in shaping river ecosystems
2022 – Encyclopedia of Inland Waters (Second Edition)
Jonathan D. Tonkin

Aim: To understand the effects of climate change and extreme events on river ecosystems. Main concepts covered: This chapter focuses on the key areas in which climate change will affect and already is affecting river ecosystems. These include species range shifts, reorganization and invasion; complex and nonlinear population, community and ecosystem responses; coupled geomorphological-ecological linkages; interactive responses with other stressors; altered flow regimes, and how these changes link with species adaptations to natural flow regimes; and thresholds and regime shifts in response to change. Conclusion/Outlook: Climate change is altering river flow and thermal regimes globally, including altering the magnitude and frequency of extreme events, and this is already having a major detrimental effect on river ecosystems. These effects are set to continue and potentially accelerate as the climate continues to change. I offer a few solutions to minimize the detrimental effects of these changes.

Journal articles

2024

87. Ecosystem-size relationships of river populations and communities
2024 – Trends in Ecology & Evolution
Angus R. McIntosh, Hamish S. Greig, Helen J. Warburton, Jonathan D. Tonkin, Catherine M. Febria

Knowledge of ecosystem-size influences on river populations and communities is integral to the balancing of human and environmental needs for water. The multiple dimensions of dendritic river networks complicate understanding of ecosystem-size influences, but could be resolved by the development of scaling relationships. We highlight the importance of physical constraints limiting predator body sizes, movements, and population sizes in small rivers, and where river contraction limits space or creates stressful conditions affecting community stability and food webs. Investigations of the scaling and contingency of these processes will be insightful because of the underlying generality and scale independence of such relationships. Doing so will also pinpoint damaging water-management practices and identify which aspects of river size can be most usefully manipulated in river restoration.

2023

86. Causes, responses, and implications of anthropogenic versus natural flow intermittence in river networks
2023 – BioScience
Thibault Datry, Amélie Truchy, Julian D Olden, Michelle H Busch, Rachel Stubbington, Walter K Dodds, Sam Zipper, Songyan Yu, Mathis L Messager, Jonathan D. Tonkin, Kendra E Kaiser, John C Hammond, Eric K Moody, Ryan M Burrows, Romain Sarremejane, Amanda G DelVecchia, Megan L Fork, Chelsea J Little, Richard H Walker, Annika W Walters, Daniel Allen

Rivers that do not flow year-round are the predominant type of running waters on Earth. Despite a burgeoning literature on natural flow intermittence (NFI), knowledge about the hydrological causes and ecological effects of human-induced, anthropogenic flow intermittence (AFI) remains limited. NFI and AFI could generate contrasting hydrological and biological responses in rivers because of distinct underlying causes of drying and evolutionary adaptations of their biota. We first review the causes of AFI and show how different anthropogenic drivers alter the timing, frequency and duration of drying, compared with NFI. Second, we evaluate the possible differences in biodiversity responses, ecological functions, and ecosystem services between NFI and AFI. Last, we outline knowledge gaps and management needs related to AFI. Because of the distinct hydrologic characteristics and ecological impacts of AFI, ignoring the distinction between NFI and AFI could undermine management of intermittent rivers and ephemeral streams and exacerbate risks to the ecosystems and societies downstream.

85. The global EPTO database: Worldwide occurrences of aquatic insects
2023 – Global Ecology and Biogeography
Afroditi Grigoropoulou, Suhaila Ab Hamid, Raúl Acosta, Emmanuel Olusegun Akindele, Salman A. Al-Shami, Florian Altermatt, Giuseppe Amatulli, David G. Angeler, Francis O. Arimoro, Jukka Aroviita, Anna Astorga-Roine, Rafael Costa Bastos, Núria Bonada, Nikos Boukas, Cecilia Brand, Vanessa Bremerich, Alex Bush, Qinghua Cai, Marcos Callisto, Kai Chen, Paulo Vilela Cruz, Olivier Dangles, Russell Death, Xiling Deng, Eduardo Domínguez, David Dudgeon, Tor Erik Eriksen, Ana Paula J. Faria, Maria João Feio, Camino Fernández-Aláez, Mathieu Floury, Francisco García-Criado, Jorge García-Girón, Wolfram Graf, Mira Grönroos, Peter Haase, Neusa Hamada, Fengzhi He, Jani Heino, Ralph Holzenthal, Kaisa-Leena Huttunen, Dean Jacobsen, Sonja C. Jähnig, Walter Jetz, Richard K. Johnson, Leandro Juen, Vincent Kalkman, Vassiliki Kati, Unique N. Keke, Ricardo Koroiva, Mathias Kuemmerlen, Simone Daniela Langhans, Raphael Ligeiro, Kris {Van Looy}, Alain Maasri, Richard Marchant, Jaime Ricardo {Garcia Marquez}, Renato T. Martins, Adriano S. Melo, Leon Metzeling, Maria Laura Miserendino, S. Jannicke Moe, Carlos Molineri, Timo Muotka, Kaisa-Riikka Mustonen, Heikki Mykrä, Jeane Marcelle {Cavalcante do Nascimento}, Francisco Valente-Neto, Peter J. Neu, Carolina Nieto, Steffen U. Pauls, Dennis R. Paulson, Blanca Rios-Touma, Marciel Elio Rodrigues, Fabio {de Oliveira Roque}, Juan Carlos {Salazar Salina}, Dénes Schmera, Astrid Schmidt-Kloiber, Deep Narayan Shah, John P. Simaika, Tadeu Siqueira, Ram Devi Tachamo-Shah, Günther Theischinger, Ross Thompson, Jonathan D. Tonkin, Yusdiel Torres-Cambas, Colin Townsend, Eren Turak, Laura Twardochleb, Beixin Wang, Liubov Yanygina, Carmen Zamora-Muñoz, Sami Domisch

Motivation Aquatic insects comprise 64% of freshwater animal diversity and are widely used as bioindicators to assess water quality impairment and freshwater ecosystem health, as well as to test ecological hypotheses. Despite their importance, a comprehensive, global database of aquatic insect occurrences for mapping freshwater biodiversity in macroecological studies and applied freshwater research is missing. We aim to fill this gap and present the Global EPTO Database, which includes worldwide geo-referenced aquatic insect occurrence records for four major taxa groups: Ephemeroptera, Plecoptera, Trichoptera and Odonata (EPTO). Main type of variables contained A total of 8,368,467 occurrence records globally, of which 8,319,689 (99%) are publicly available. The records are attributed to the corresponding drainage basin and sub-catchment based on the Hydrography90m dataset and are accompanied by the elevation value, the freshwater ecoregion and the protection status of their location. Spatial location and grain The database covers the global extent, with 86% of the observation records having coordinates with at least four decimal digits (11.1 m precision at the equator) in the World Geodetic System 1984 (WGS84) coordinate reference system. Time period and grain Sampling years span from 1951 to 2021. Ninety-nine percent of the records have information on the year of the observation, 95% on the year and month, while 94% have a complete date. In the case of seven sub-datasets, exact dates can be retrieved upon communication with the data contributors. Major taxa and level of measurement Ephemeroptera, Plecoptera, Trichoptera and Odonata, standardized at the genus taxonomic level. We provide species names for 7,727,980 (93%) records without further taxonomic verification. Software format The entire tab-separated value (.csv) database can be downloaded and visualized at https://glowabio.org/project/epto_database/. Fifty individual datasets are also available at https://fred.igb-berlin.de, while six datasets have restricted access. For the latter, we share metadata and the contact details of the authors.

84. Priorities for synthesis research in ecology and environmental science
2023 – Ecosphere
Benjamin S. Halpern, Carl Boettiger, Michael C. Dietze, Jessica A. Gephart, Patrick Gonzalez, Nancy B. Grimm, Peter M. Groffman, Jessica Gurevitch, Sarah E. Hobbie, Kimberly J. Komatsu, Kristy J. Kroeker, Heather J. Lahr, David M. Lodge, Christopher J. Lortie, Julie S. S. Lowndes, Fiorenza Micheli, Hugh P. Possingham, Mary H. Ruckelshaus, Courtney Scarborough, Chelsea L. Wood, Grace C. Wu, Lina Aoyama, Eva E. Arroyo, Christie A. Bahlai, Erin E. Beller, Rachael E. Blake, Karrigan S. Bork, Trevor A. Branch, Norah E. M. Brown, Julien Brun, Emilio M. Bruna, Lauren B. Buckley, Jessica L. Burnett, Max C. N. Castorani, Samantha H. Cheng, Sarah C. Cohen, Jessica L. Couture, Larry B. Crowder, Laura E. Dee, Arildo S. Dias, Ignacio J. Diaz-Maroto, Martha R. Downs, Joan C. Dudney, Erle C. Ellis, Kyle A. Emery, Jacob G. Eurich, Bridget E. Ferriss, Alexa Fredston, Hikaru Furukawa, Sara A. Gagné, Sarah R. Garlick, Colin J. Garroway, Kaitlyn M. Gaynor, Angélica L. González, Eliza M. Grames, Tamar Guy-Haim, Ed Hackett, Lauren M. Hallett, Tamara K. Harms, Danielle E. Haulsee, Kyle J. Haynes, Elliott L. Hazen, Rebecca M. Jarvis, Kristal Jones, Gaurav S. Kandlikar, Dustin W. Kincaid, Matthew L. Knope, Anil Koirala, Jurek Kolasa, John S. Kominoski, Julia Koricheva, Lesley T. Lancaster, Jake A. Lawlor, Heili E. Lowman, Frank E. Muller-Karger, Kari E. A. Norman, Nan Nourn, Casey C. O’Hara, Suzanne X. Ou, Jacqueline L. Padilla-Gamino, Paula Pappalardo, Ryan A. Peek, Dominique Pelletier, Stephen Plont, Lauren C. Ponisio, Cristina Portales-Reyes, Diogo B. Provete, Eric J. Raes, Carlos Ramirez-Reyes, Irene Ramos, Sydne Record, Anthony J. Richardson, Roberto Salguero-Gómez, Erin V. Satterthwaite, Chloé Schmidt, Aaron J. Schwartz, Craig R. See, Brendan D. Shea, Rachel S. Smith, Eric R. Sokol, Christopher T. Solomon, Trisha Spanbauer, Paris V. Stefanoudis, Beckett W. Sterner, Vitor Sudbrack, Jonathan D. Tonkin, Ashley R. Townes, Mireia Valle, Jonathan A. Walter, Kathryn I. Wheeler, William R. Wieder, David R. Williams, Marten Winter, Barbora Winterova, Lucy C. Woodall, Adam S. Wymore, Casey Youngflesh

Synthesis research in ecology and environmental science improves understanding, advances theory, identifies research priorities, and supports management strategies by linking data, ideas, and tools. Accelerating environmental challenges increases the need to focus synthesis science on the most pressing questions. To leverage input from the broader research community, we convened a virtual workshop with participants from many countries and disciplines to examine how and where synthesis can address key questions and themes in ecology and environmental science in the coming decade. Seven priority research topics emerged: (1) diversity, equity, inclusion, and justice (DEIJ), (2) human and natural systems, (3) actionable and use-inspired science, (4) scale, (5) generality, (6) complexity and resilience, and (7) predictability. Additionally, two issues regarding the general practice of synthesis emerged: the need for increased participant diversity and inclusive research practices; and increased and improved data flow, access, and skill-building. These topics and practices provide a strategic vision for future synthesis in ecology and environmental science.

83. Forecasting the future of life in Antarctica
2023 – Trends in Ecology & Evolution
Gabrielle Koerich, Ceridwen I. Fraser, Charles K. Lee, Fraser J. Morgan, Jonathan D. Tonkin

Antarctic ecosystems are under increasing anthropogenic pressure, but efforts to predict the responses of Antarctic biodiversity to environmental change are hindered by considerable data challenges. Here, we illustrate how novel data capture technologies provide exciting opportunities to sample Antarctic biodiversity at wider spatiotemporal scales. Data integration frameworks, such as point process and hierarchical models, can mitigate weaknesses in individual data sets, improving confidence in their predictions. Increasing process knowledge in models is imperative to achieving improved forecasts of Antarctic biodiversity, which can be attained for data-limited species using hybrid modelling frameworks. Leveraging these state-of-the-art tools will help to overcome many of the data scarcity challenges presented by the remoteness of Antarctica, enabling more robust forecasts both near- and long-term.

82. The power of forecasts to advance ecological theory
2023 – Methods in Ecology and Evolution
Abigail S. L. Lewis, Christine R. Rollinson, Andrew J. Allyn, Jaime Ashander, Stephanie Brodie, Cole B. Brookson, Elyssa Collins, Michael C. Dietze, Amanda S. Gallinat, Noel Juvigny-Khenafou, Gerbrand Koren, Daniel J. McGlinn, Hassan Moustahfid, Jody A. Peters, Nicholas R. Record, Caleb J. Robbins, Jonathan D. Tonkin, Glenda M. Wardle

Ecological forecasting provides a powerful set of methods for predicting short- and long-term change in living systems. Forecasts are now widely produced, enabling proactive management for many applied ecological problems. However, despite numerous calls for an increased emphasis on prediction in ecology, the potential for forecasting to accelerate ecological theory development remains underrealized. Here, we provide a conceptual framework describing how ecological forecasts can energize and advance ecological theory. We emphasize the many opportunities for future progress in this area through increased forecast development, comparison and synthesis. Our framework describes how a forecasting approach can shed new light on existing ecological theories while also allowing researchers to address novel questions. Through rigorous and repeated testing of hypotheses, forecasting can help to refine theories and understand their generality across systems. Meanwhile, synthesizing across forecasts allows for the development of novel theory about the relative predictability of ecological variables across forecast horizons and scales. We envision a future where forecasting is integrated as part of the toolset used in fundamental ecology. By outlining the relevance of forecasting methods to ecological theory, we aim to decrease barriers to entry and broaden the community of researchers using forecasting for fundamental ecological insight.

81. Matrix community models for ecology and evolution
2023 – npj Biodiversity
David A. Lytle, Jonathan D. Tonkin

Ecological communities are shaped by biotic interactions as well as environmental forces, and both must be incorporated to obtain models capable of forecasting realistic community dynamics. Many community models first specify pairwise biotic interactions and then secondarily examine how extrinsic factors such as abiotic conditions affect species abundances. A disadvantage of this approach is that the species interactions themselves are often environment and context specific, making parameterization difficult. We propose an alternative approach, matrix community models (MCMs), which are sets of matrix population models linked by an assumption of aggregate density dependence. MCMs incorporate detailed species autecology but are neutral with respect to pairwise species interactions, instead allowing interactions to be revealed within the model structure. These model-revealed species interactions, including competitive exclusion, facilitation, and interference competition, shape the distribution and abundance of species within communities and generate empirically testable predictions about species interactions. We develop a framework for building MCMs using vital rates in a stochastic, multispecies framework. Single-species matrix population models are connected via an assumption of aggregate density dependence, pairwise species interactions are estimated with sensitivity analysis, and community trajectories are analyzed under different environmental regimes using standard statistical tools and network analysis. MCMs have the advantage that pairwise species interactions need not be specified a priori, and that mechanistic demographic-environment linkages permit forecasting of community dynamics under novel, non-stationary environmental regimes. A challenge is that species’ autecological vital rates, such as fecundity, growth and survivorship, must be measured under a diverse range of environmental conditions to parameterize the models. We illustrate the approach with examples and discuss prospects for future theoretical and empirical developments.

80. Climate change impacts on Aotearoa New Zealand: a horizon scan approach
2023 – Journal of the Royal Society of New Zealand
Cate Macinnis-Ng, Ilze Ziedins, Hamza Ajmal, W. Troy Baisden, Shaun Hendy, Adrian McDonald, Rebecca Priestley, Rhian A. Salmon, Emma L. Sharp, Jonathan D. Tonkin, Sandra Velarde, Krushil Watene, William Godsoe

Many of the implications of climate change for Aotearoa (New Zealand) remain unclear. To identify so-far unseen or understudied threats and opportunities related to climate change we applied a horizon-scanning process. First, we collated 171 threats and opportunities across our diverse fields of research. We then scored each item for novelty and potential impact and finally reduced the list to ten threats and ten opportunities through a prioritisation process. Within the 20 items presented in this paper, we uncover a range of climate-related costs and benefits. Unexpected opportunities evolve from economic reorganisation and changes to perspectives. The threats we highlight include the overall failure to interconnect siloed policy responses, as well as those relating to extreme events and feedbacks, as well as pressures that undermine the coherence of society. A major theme of our work is that climate change effects in Aotearoa are likely to transgress the boundaries of research disciplines, industry sectors and policy systems, emphasising the importance of developing transdisciplinary methods and approaches. We use this insight to connect potential responses to climate change with Aotearoa’s culture and geography.

79. Taxonomic and functional reorganization in Central European stream macroinvertebrate communities over 25 years
2023 – Science of The Total Environment
Alessandro Manfrin, Francesca Pilotto, Stefano Larsen, Jonathan D. Tonkin, Armin W. Lorenz, Peter Haase, Stefan Stoll

Climate warming can lead to a replacement of species that favour cold temperatures by species that favour warm temperatures. However, the implications of such thermic shifts for the functioning of ecosystems remain poorly understood. Here, we used stream macroinvertebrate biological and ecological traits to quantify the relative contribution of cold, intermediate and warm temperature-adapted taxa to changes in community functional diversity (FD) using a dataset of 3781 samples collected in Central Europe over 25~years, from 1990 to 2014. Our analyses indicated that functional diversity of stream macroinvertebrate communities increased over the study period. This gain was driven by a net 39~% increase in the richness of taxa that favour intermediate temperatures, which comprise the highest share in the community, and to a 97~% increase in the richness of taxa that favour warm temperatures. These warm temperature-adapted taxa displayed a distinct and more diverse suite of functional traits compared to the cold temperature-adapted group and thus contributed disproportionately to local FD on a per-taxon basis. At the same time, taxonomic beta-diversity declined significantly within each thermal group, in association with increasing local taxon richness. This study shows that over recent decades, small low-mountain streams in Central Europe have experienced a process of thermophilization and increasing functional diversity at local scales. However, a progressive homogenisation occurred at the regional scale, with communities converging towards similar taxonomic composition. As the reported increase in local functional diversity can be attributed mostly to the intermediate temperature-adapted taxa and a few expanding warm temperature-adapted taxa, these patterns could mask more subtle loss of sensitive cold temperature-adapted taxa with irreplaceable functional traits. In light of increasing climate warming, preservation of cold habitat refuges, should be considered a priority in river conservation.

78. A metasystem approach to designing environmental flows
2023 – BioScience
Mathis L Messager, Julian D Olden, Jonathan D. Tonkin, Rachel Stubbington, Jane S Rogosch, Michelle H Busch, Chelsea J Little, Annika W Walters, Carla L Atkinson, Margaret Shanafield, Songyan Yu, Kate S Boersma, David A Lytle, Richard H Walker, Ryan M Burrows, Thibault Datry

Accelerating the design and implementation of environmental flows (e-flows) is essential to curb the rapid, ongoing loss of freshwater biodiversity and the benefits it provides to people. However, the effectiveness of e-flow programs may be limited by a singular focus on ensuring adequate flow conditions at local sites, which overlooks the role of other ecological processes. Recent advances in metasystem ecology have shown that biodiversity patterns and ecosystem functions across river networks result from the interplay of local (environmental filtering and biotic interactions) and regional (dispersal) ecological processes. No guidelines currently exist to account for these processes in designing e-flows. We address this gap by providing a step-by-step operational framework that outlines how e-flows can be designed to conserve or restore metasystem dynamics. Our recommendations are relevant to diverse regulatory contexts and can improve e-flow outcomes even in basins with limited in situ data.

77. Understanding temporal variability across trophic levels and spatial scales in freshwater ecosystems
2023 – Ecology
Tadeu Siqueira, Charles P. Hawkins, Julian D. Olden, Jonathan D. Tonkin, Lise Comte, Victor S. Saito, Thomas L. Anderson, Gedimar P. Barbosa, Núria Bonada, Claudia C. Bonecker, Miguel Cañedo-Argüelles, Thibault Datry, Michael B. Flinn, Pau Fortuño, Gretchen A. Gerrish, Peter Haase, Matthew J. Hill, James M. Hood, Kaisa-Leena Huttunen, Michael J. Jeffries, Timo Muotka, Daniel R. O’Donnell, Riku Paavola, Petr Paril, Michael J. Paterson, Christopher J. Patrick, Gilmar Perbiche-Neves, Luzia C. Rodrigues, Susanne C. Schneider, Michal Straka, Albert Ruhi

A tenet of ecology is that temporal variability in ecological structure and processes tends to decrease with increasing spatial scales (from locales to regions) and levels of biological organization (from populations to communities). However, patterns in temporal variability across trophic levels and the mechanisms that produce them remain poorly understood. Here we analyzed the abundance time series of spatially structured communities (i.e., metacommunities) spanning basal resources to top predators from 355 freshwater sites across three continents. Specifically, we used a hierarchical partitioning method to disentangle the propagation of temporal variability in abundance across spatial scales and trophic levels. We then used structural equation modeling to determine if the strength and direction of relationships between temporal variability, synchrony, biodiversity, and environmental and spatial settings depended on trophic level and spatial scale. We found that temporal variability in abundance decreased from producers to tertiary consumers but did so mainly at the local scale. Species population synchrony within sites increased with trophic level, whereas synchrony among communities decreased. At the local scale, temporal variability in precipitation and species diversity were associated with population variability (linear partial coefficient, {\(\beta\)} = 0.23) and population synchrony ({\(\beta\)} = -0.39) similarly across trophic levels, respectively. At the regional scale, community synchrony was not related to climatic or spatial predictors, but the strength of relationships between metacommunity variability and community synchrony decreased systematically from top predators ({\(\beta\)} = 0.73) to secondary consumers ({\(\beta\)} = 0.54), to primary consumers ({\(\beta\)} = 0.30) to producers ({\(\beta\)} = 0). Our results suggest that mobile predators may often stabilize metacommunities by buffering variability that originates at the base of food webs. This finding illustrates that the trophic structure of metacommunities, which integrates variation in organismal body size and its correlates, should be considered when investigating ecological stability in natural systems. More broadly, our work advances the notion that temporal stability is an emergent property of ecosystems that may be threatened in complex ways by biodiversity loss and habitat fragmentation.

76. Diversity-stability relationships across organism groups and ecosystem types become decoupled across spatial scales
2023 – Ecology
Nathan I. Wisnoski, Riley Andrade, Max C. N. Castorani, Christopher P. Catano, Aldo Compagnoni, Thomas Lamy, Nina K. Lany, Luca Marazzi, Sydne Record, Annie C. Smith, Christopher M. Swan, Jonathan D. Tonkin, Nicole M. Voelker, Phoebe L. Zarnetske, Eric R. Sokol

The relationship between biodiversity and stability, or its inverse, temporal variability, is multidimensional and complex. Temporal variability in aggregate properties, like total biomass or abundance, is typically lower in communities with higher species diversity (i.e., the diversity–stability relationship [DSR]). At broader spatial extents, regional-scale aggregate variability is also lower with higher regional diversity (in plant systems) and with lower spatial synchrony. However, focusing exclusively on aggregate properties of communities may overlook potentially destabilizing compositional shifts. It is not yet clear how diversity is related to different components of variability across spatial scales, nor whether regional DSRs emerge across a broad range of organisms and ecosystem types. To test these questions, we compiled a large collection of long-term metacommunity data spanning a wide range of taxonomic groups (e.g., birds, fish, plants, invertebrates) and ecosystem types (e.g., deserts, forests, oceans). We applied a newly developed quantitative framework for jointly analyzing aggregate and compositional variability across scales. We quantified DSRs for composition and aggregate variability in local communities and metacommunities. At the local scale, more diverse communities were less variable, but this effect was stronger for aggregate than compositional properties. We found no stabilizing effect of {\(\gamma\)}-diversity on metacommunity variability, but {\(\beta\)}-diversity played a strong role in reducing compositional spatial synchrony, which reduced regional variability. Spatial synchrony differed among taxa, suggesting differences in stabilization by spatial processes. However, metacommunity variability was more strongly driven by local variability than by spatial synchrony. Across a broader range of taxa, our results suggest that high {\(\gamma\)}-diversity does not consistently stabilize aggregate properties at regional scales without sufficient spatial {\(\beta\)}-diversity to reduce spatial synchrony.

2022

75. Seasonal variation in the metacommunity structure of benthic macroinvertebrates in a large river-connected floodplain lake
2022 – Ecological Indicators
Zhengfei Li, Jonathan D. Tonkin, Xingliang Meng, Zhenyuan Liu, Junqian Zhang, Xiao Chen, Zhicai Xie, Jani Heino

To improve our understanding on the temporal aspects of metacommunity structure, we focused on benthic macroinvertebrates collected seasonally (i.e., wet, drying, dry and rewetting seasons) in Dongting Lake, a large subtropical floodplain lake in China. We employed the elements of metacommunity structure (EMS) framework and variation partitioning to examine whether metacommunity structure and its underlying mechanisms vary among seasons with distinct biotic and abiotic features. We found gradual shifts in the main assembly mechanisms throughout the year, from apparent spatial structuring (potentially indicative of mass effects) in the wet season to more environmental filtering dynamics in the dry season. When the degree of connectivity was high in the wet season, the benthic metacommunity was characterized by nested structure associated with clumped species loss, and was shaped mainly by spatial processes. However, quasi-Clemensian structure was assigned to metacommunities in the transitional seasons with intermediate connectivity, during which environmental variables were more important than spatial factors in describing community structure. When the degree of connectivity was low in the dry season, the benthic metacommunity displayed Clementsian structure, which was configured solely by environmental variables. The rapid shifts in metacommunity dynamics between seasons mainly result from the considerable changes in the hydrological conditions of Dongting Lake, as the studied system varies from lacustrine to fluvial phases within a single year. Taken together, our results revealed that taking temporal aspects into account gives a better insight into metacommunity organization, especially when the studied systems embrace remarkable variability in hydrological regimes.

74. A global agenda for advancing freshwater biodiversity research
2022 – Ecology Letters
Alain Maasri, Sonja C. Jähnig, Mihai C. Adamescu, Rita Adrian, Claudio Baigun, Donald J. Baird, Angelica Batista-Morales, Núria Bonada, Lee E. Brown, Qinghua Cai, Joao V. Campos-Silva, Viola Clausnitzer, Topiltzin Contreras-MacBeath, Steven J. Cooke, Thibault Datry, Gonzalo Delacámara, Luc {De Meester}, Klaus-Douwe B. Dijkstra, Van Tu Do, Sami Domisch, David Dudgeon, Tibor Erös, Hendrik Freitag, Joerg Freyhof, Jana Friedrich, Martin Friedrichs-Manthey, Juergen Geist, Mark O. Gessner, Peter Goethals, Matthew Gollock, Christopher Gordon, Hans-Peter Grossart, Georges Gulemvuga, Pablo E. Gutiérrez-Fonseca, Peter Haase, Daniel Hering, Hans Jürgen Hahn, Charles P. Hawkins, Fengzhi He, Jani Heino, Virgilio Hermoso, Zeb Hogan, Franz Hölker, Jonathan M. Jeschke, Meilan Jiang, Richard K. Johnson, Gregor Kalinkat, Bakhtiyor K. Karimov, Aventino Kasangaki, Ismael A. Kimirei, Bert Kohlmann, Mathias Kuemmerlen, Jan J. Kuiper, Benjamin Kupilas, Simone D. Langhans, Richard Lansdown, Florian Leese, Francis S. Magbanua, Shin-ichiro S. Matsuzaki, Michael T. Monaghan, Levan Mumladze, Javier Muzon, Pierre A. {Mvogo Ndongo}, Jens C. Nejstgaard, Oxana Nikitina, Clifford Ochs, Oghenekaro Nelson Odume, Jeffrey J. Opperman, Harmony Patricio, Steffen U. Pauls, Rajeev Raghavan, Alonso Ramírez, Bindiya Rashni, Vere Ross-Gillespie, Michael J. Samways, Ralf B. Schäfer, Astrid Schmidt-Kloiber, Ole Seehausen, Deep Narayan Shah, Subodh Sharma, Janne Soininen, Nike Sommerwerk, Jason D. Stockwell, Frank Suhling, Ram Devi {Tachamo Shah}, Rebecca E. Tharme, James H. Thorp, David Tickner, Klement Tockner, Jonathan D. Tonkin, Mireia Valle, Jean Vitule, Martin Volk, Ding Wang, Christian Wolter, Susanne Worischka

Global freshwater biodiversity is declining dramatically, and meeting the challenges of this crisis requires bold goals and the mobilisation of substantial resources. While the reasons are varied, investments in both research and conservation of freshwater biodiversity lag far behind those in the terrestrial and marine realms. Inspired by a global consultation, we identify 15 pressing priority needs, grouped into five research areas, in an effort to support informed stewardship of freshwater biodiversity. The proposed agenda aims to advance freshwater biodiversity research globally as a critical step in improving coordinated actions towards its sustainable management and conservation.

73. Climate and land-use driven reorganisation of structure and function in river macroinvertebrate communities
2022 – Ecography
Théophile L. Mouton, Fabien Leprieur, Mathieu Floury, Fabrice Stephenson, Piet Verburg, Jonathan D. Tonkin

Understanding temporal changes in the composition of species communities over spatial and temporal scales relevant to conservation management is crucial for preventing further biodiversity declines. Here, we assessed patterns and potential drivers of taxonomic and functional temporal {\(\beta\)} diversity over 26 years (1991–2016) of 64 river macroinvertebrate communities, and the length of New Zealand (37{\(^\circ\)}00’N, 46{\(^\circ\)}00’S). We further examined changes in population size and range shifts of species pools, and related these to taxonomy and functional traits. We found increasing climate and land-use driven differences in both the taxonomic and functional composition of communities over time, coupled with poleward species colonisations and increasing extirpations in northern locations. Increases in population and species range size were more prevalent than decreases in population and range size. Species shifted their ranges towards higher latitudes on average by 50 km per decade. Despite little to no relationship with taxonomy, we uncovered distinct relationships between functional traits and population trends and latitudinal species range shifts. Species with a high number of reproductive cycles per year and long-life duration of adults tended to increase their population size, while larger size species with a high number of descendants per reproductive cycle tended to shift their range towards more southern latitudes. Our results suggest that the intensity of disturbances, the geographic location of individuals and communities, and species ecological and functional characteristics, are major determinants of riverine biodiversity reorganisation in the Anthropocene.

72. Spatial mismatch in diversity facets reveals contrasting protection for New Zealand’s cetacean biodiversity
2022 – Biological Conservation
Théophile L. Mouton, Fabrice Stephenson, Leigh G. Torres, Will Rayment, Tom Brough, Matthew McLean, Jonathan D. Tonkin, Camille Albouy, Fabien Leprieur

Cetaceans play key roles in the world’s ecosystems and provide important economic and social benefits. New Zealand’s Exclusive Economic Zone is a global biodiversity hotspot for cetaceans and benefits from a system of marine protected areas (MPAs). However, spatial patterns of cetacean biodiversity and their overlap with MPAs have never been assessed. We quantify this overlap by using a comprehensive cetacean at-sea sightings database, high-resolution environmental data layers, and information on ecological and evolutionary characteristics of each species to model spatial patterns of taxonomic, functional, and phylogenetic diversity of cetaceans. We examine areas of congruence among hotspots of richness and uniqueness components of biodiversity and measure the contribution of species to biodiversity. We find that cetacean taxonomic and phylogenetic diversity are spatially mismatched with MPAs, but this is less true for functional diversity. Hotspots of congruence among richness indices are located on the continental shelf break, whereas hotspots of uniqueness indices are located closer to shore on the continental shelf. Seven species have high contributions to biodiversity, with blue whale being the only species being evolutionarily distinct, functionally unique, specialised and globally endangered. Our results underline the potential of multicomponent biodiversity indices, their spatial congruence, and the contribution of species to biodiversity to be used as guides for a strategic placement and expansion of MPAs to protect biodiversity.

71. Environmental flows in an uncertain future
2022 – Frontiers in Environmental Science
Eric D. Stein, Avril C. Horne, Rebecca E. Tharme, Jonathan D. Tonkin

Editorial on the Research Topic “Environmental flows in an uncertain future

2021

70. Hydropeaking intensity and dam proximity limit aquatic invertebrate diversity in the Colorado River Basin
2021 – Ecosphere
Erin F. Abernethy, Jeffrey D. Muehlbauer, Theodore A. Kennedy, Jonathan D. Tonkin, Richard Van Driesche, David A. Lytle

River biodiversity is threatened globally by hydropower dams, and there is a need to understand how dam management favors certain species while filtering out others. We examined aquatic invertebrate communities within the tailwaters 0–24 km downstream of seven large hydropower dams in the Colorado River Basin of the western United States. We quantified aquatic invertebrate dominance, richness, abundance, and biomass at multiple locations within individual tailwaters and across the basin and identified biological community responses associated with dam operations and distance from dam. We found that each tailwater was dominated by 3–7 invertebrate taxa, accounting for 95% of total abundance. Half of these dominant taxa were non-insect, non-flying species and thus were unavailable to terrestrial consumers. Consistent with previous studies, aquatic insects and sensitive taxa were negatively associated with hydropeaking intensity (magnitude of daily flow fluctuations associated with hydropower generation), which limits the composition and potentially the quality of the invertebrate food base. While total invertebrate abundance and biomass did not change with increasing distance downstream from dams, insect and sensitive taxa richness, abundance, and biomass all increased, suggesting that impacts of hydropeaking are most acute immediately downstream of dams. Our results demonstrate that tailwaters experiencing hydropeaking support high abundances of aquatic invertebrate, but the diversity of these communities is low.

69. Toward a generalizable framework of disturbance ecology through crowdsourced science
2021 – Frontiers in Ecology and Evolution
Emily B. Graham, Colin Averill, Ben Bond-Lamberty, Joseph E. Knelman, Stefan Krause, Ariane L. Peralta, Ashley Shade, A. Peyton Smith, Susan J. Cheng, Nicolas Fanin, Cathryn Freund, Patricia E. Garcia, Sean M. Gibbons, Marc W. {Van Goethem}, Marouen Ben Guebila, Julia Kemppinen, Robert J. Nowicki, Juli G. Pausas, Samuel P. Reed, Jennifer Rocca, Aditi Sengupta, Debjani Sihi, Marie Simonin, Michał Słowiński, Seth A. Spawn, Ira Sutherland, Jonathan D. Tonkin, Nathan I. Wisnoski, Samuel C. Zipper, Contributor Consortium, Arie Staal, Bhavna Arora, Callie Oldfield, Dipankar Dwivedi, Erin Larson, Ezequiel Santillan, J. {Aaron Hogan}, Jeff Atkins, Jianqiu Zheng, Jonas Lembrechts, Kaizad Patel, Kelsey Copes-Gerbitz, Kevin Winker, Laura Mudge, Mark Wong, Martin Nuñez, Miska Luoto, Rebecca Barnes

Disturbances fundamentally alter ecosystem functions, yet predicting their impacts remains a key scientific challenge. While the study of disturbances is ubiquitous across many ecological disciplines, there is no agreed-upon, cross-disciplinary foundation for discussing or quantifying the complexity of disturbances, and no consistent terminology or methodologies exist. This inconsistency presents an increasingly urgent challenge due to accelerating global change and the threat of interacting disturbances that can destabilize ecosystem responses. By harvesting the expertise of an interdisciplinary cohort of contributors spanning 42 institutions across 15 countries, we identified an essential limitation in disturbance ecology: the word disturbance is used interchangeably to refer to both the events that cause, and the consequences of, ecological change, despite fundamental distinctions between the two meanings. In response, we developed a generalized framework of ecosystem disturbances to reconcile this limitation, providing a well-defined lexicon for understanding disturbance across perspectives and scales. The framework results from ideas that resonate across multiple scientific disciplines and provides a baseline standard to compare disturbances across fields. This framework can be supplemented by discipline-specific variables to provide maximum benefit to both inter- and intra-disciplinary research. To support future synthesis or meta-analysis of disturbance research, we also encourage researchers to be explicit in how they define disturbance drivers and impacts, recommend minimum reporting standards that studies should detail about the magnitude, duration, and rate of change of driver and response variables of a disturbance, regardless of scale. We discuss the primary factors we considered when developing a baseline framework and propose four future directions to advance our interdisciplinary understanding of disturbances and their social-ecological impacts: integrating across ecological scales, understanding disturbance interactions, establishing baselines and trajectories, and developing process-based models and ecological forecasting initiatives. Our experience through this process motivates us to encourage the wider scientific community to continue to explore new approaches for leveraging Open Science principles in generating creative and multidisciplinary ideas.

68. Revisiting global trends in freshwater insect biodiversity
2021 – WIREs Water
Sonja C. Jähnig, Viktor Baranov, Florian Altermatt, Peter Cranston, Martin Friedrichs-Manthey, Juergen Geist, Fengzhi He, Jani Heino, Daniel Hering, Franz Hölker, Jonas Jourdan, Gregor Kalinkat, Jens Kiesel, Florian Leese, Alain Maasri, Michael T. Monaghan, Ralf B. Schäfer, Klement Tockner, Jonathan D. Tonkin, Sami Domisch

A recent global meta-analysis reported a decrease in terrestrial but increase in freshwater insect abundance and biomass (van Klink et al., Science 368, p. 417). The authors suggested that water quality has been improving, thereby challenging recent reports documenting drastic global declines in freshwater biodiversity. We raise two major concerns with the meta-analysis and suggest that these account for the discrepancy with the declines reported elsewhere. First, total abundance and biomass alone are poor indicators of the status of freshwater insect assemblages, and the observed differences may well have been driven by the replacement of sensitive species with tolerant ones. Second, many of the datasets poorly represent global trends and reflect responses to local conditions or nonrandom site selection. We conclude that the results of the meta-analysis should not be considered indicative of an overall improvement in the condition of freshwater ecosystems. This article is categorized under: Water and Life {\(>\)} Conservation, Management, and Awareness

67. Physiology, niche characteristics and extreme events: Current and future habitat suitability of a rhodolith-forming species in the Southwestern Atlantic
2021 – Marine Environmental Research
Gabrielle Koerich, Giulia Burle Costa, Marina Nasri Sissini, Carlos Lopez Ortiz, Beatriz Feltrin Canever, Willian Oliveira, Jonathan D. Tonkin, Paulo Antunes Horta

Given the ecological and biogeochemical importance of rhodolith beds, it is necessary to investigate how future environmental conditions will affect these organisms. We investigated the impacts of increased nutrient concentrations, acidification, and marine heatwaves on the performance of the rhodolith-forming species Lithothamnion crispatum in a short-term experiment, including the recovery of individuals after stressor removal. Furthermore, we developed an ecological niche model to establish which environmental conditions determine its current distribution along the Brazilian coast and to project responses to future climate scenarios. Although L. crispatum suffered a reduction in photosynthetic performance when exposed to stressors, they returned to pre-experiment values following the return of individuals to control conditions. The model showed that the most important variables in explaining the current distribution of L. crispatum on the Brazilian coast were maximum nitrate and temperature. In future ocean conditions, the model predicted a range expansion of habitat suitability for this species of approximately 58.5% under RCP 8.5. Physiological responses to experimental future environmental conditions corroborated model predictions of the expansion of this species’ habitat suitability in the future. This study, therefore, demonstrates the benefits of applying combined approaches to examine potential species responses to climate-change drivers from multiple angles.

66. The dual nature of metacommunity variability
2021 – Oikos
Thomas Lamy, Nathan I. Wisnoski, Riley Andrade, Max C. N. Castorani, Aldo Compagnoni, Nina Lany, Luca Marazzi, Sydne Record, Christopher M. Swan, Jonathan D. Tonkin, Nicole Voelker, Shaopeng Wang, Phoebe L. Zarnetske, Eric R. Sokol

There is increasing interest in measuring ecological stability to understand how communities and ecosystems respond to broad-scale global changes. One of the most common approaches is to quantify the variation through time in community or ecosystem aggregate attributes (e.g. total biomass), referred to as aggregate variability. It is now widely recognized that aggregate variability represents only one aspect of communities and ecosystems, and compositional variability, the changes in the relative frequency of species in an assemblage, is equally important. Recent contributions have also begun to explore ecological stability at regional spatial scales, where interconnected local communities form metacommunities, a key concept in managing complex landscapes. However, the conceptual frameworks and measures of ecological stability in space have only focused on aggregate variability, leaving a conceptual gap. Here, we address this gap with a novel framework for quantifying the aggregate and compositional variability of communities and ecosystems through space and time. We demonstrate that the compositional variability of a metacommunity depends on the degree of spatial synchrony in compositional trajectories among local communities. We then provide a conceptual framework in which compositional variability of 1) the metacommunity through time and 2) among local communities combine into four archetype scenarios: spatial stasis (low/low), spatial synchrony (high/low), spatial asynchrony (high/high) and spatial compensation (low/high). We illustrate this framework based on numerical examples and a case study of a macroalgal metacommunity in which low spatial synchrony reduced variability in aggregate biomass at the metacommunity scale, while masking high spatial synchrony in compositional trajectories among local communities. Finally, we discuss the role of dispersal, environmental heterogeneity, species interactions and suggest future avenues. We believe this framework will be helpful for considering both aspects of variability simultaneously, which is important to better understand ecological stability in natural and complex landscapes in response to environmental changes.

65. Distance decay of benthic macroinvertebrate communities in a mountain river network: Do dispersal routes and dispersal ability matter?
2021 – Science of The Total Environment
Zhengfei Li, Xiao Chen, Xiaoming Jiang, Jonathan D. Tonkin, Zhicai Xie, Jani Heino

Environmental heterogeneity and dispersal limitation are important drivers of beta diversity; however, their relative influence on the two fundamental components of beta diversity (i.e., species replacement and richness difference) has not been fully examined in montane streams. Here, we examined the relative importance of local environmental gradients and three physical distance matrices (i.e., overland, watercourse and cost distances) on beta diversity and its two components for a macroinvertebrate metacommunity in a stream network. To provide additional insights into community assembly, we also analysed variation in two deconstructed sub-communities based on dispersal ability (i.e., weak and strong dispersers). Both environmental filters and physical distances (dispersal limitation) drove patterns of overall beta diversity, with the former generally prevailing over the latter. Species replacement components showed stronger correlations with environmental gradients than physical distances, while the opposite is true for the richness difference components. Overland distances were generally more important than cost and watercourse distances for community dissimilarity of stream macroinvertebrates, implying that lateral dispersal out of stream corridors through flight was the major dispersal route in the studied steam network. As expected, community dissimilarity of strong dispersers was primarily shaped by environmental filtering, while community dissimilarity of weak dispersers was associated with the joint effects of environmental filtering and dispersal limitation. Our findings demonstrate that partitioning overall dissimilarity into species replacement and richness difference provides more insights into the processes driving spatial variability in biological communities compared with the utilization of total beta diversity alone. Our results support the notion that maintaining environmental heterogeneity and natural connectivity of stream networks should be effective measures to conserve regional biodiversity.

64. The application of metacommunity theory to the management of riverine ecosystems
2021 – WIREs Water
Christopher J. Patrick, Kurt E. Anderson, Brown L. Brown, Charles P. Hawkins, Anya Metcalfe, Parsa Saffarinia, Tadeu Siqueira, Christopher M. Swan, Jonathan D. Tonkin, Lester L. Yuan

River managers strive to use the best available science to sustain biodiversity and ecosystem function. To achieve this goal requires consideration of processes at different scales. Metacommunity theory describes how multiple species from different communities potentially interact with local-scale environmental drivers to influence population dynamics and community structure. However, this body of knowledge has only rarely been used to inform management practices for river ecosystems. In this article, we present a conceptual model outlining how the metacommunity processes of local niche sorting and dispersal can influence the outcomes of management interventions and provide a series of specific recommendations for applying these ideas as well as research needs. In all cases, we identify situations where traditional approaches to riverine management could be enhanced by incorporating an understanding of metacommunity dynamics. A common theme is developing guidelines for assessing the metacommunity context of a site or region, evaluating how that context may affect the desired outcome, and incorporating that understanding into the planning process and methods used. To maximize the effectiveness of management activities, scientists, and resource managers should update the toolbox of approaches to riverine management to reflect theoretical advances in metacommunity ecology. This article is categorized under: Water and Life {\(>\)} Nature of Freshwater Ecosystems Water and Life {\(>\)} Conservation, Management, and Awareness Water and Life {\(>\)} Methods

63. Novel insights to be gained from applying metacommunity theory to long-term, spatially replicated biodiversity data
2021 – Frontiers in Ecology and Evolution
Sydne Record, Nicole M. Voelker, Phoebe L. Zarnetske, Nathan I. Wisnoski, Jonathan D. Tonkin, Christopher Swan, Luca Marazzi, Nina Lany, Thomas Lamy, Aldo Compagnoni, Max C. N. Castorani, Riley Andrade, Eric R. Sokol

Global loss of biodiversity and associated ecosystem services are occurring at an alarming rate. Metacommunity theory provides a framework to investigate multi-scale processes that drive change in biodiversity across space and time. Short-term ecological studies across space have progressed our understanding of biodiversity through a metacommunity lens, however, have been limited in their ability to explain which processes, at which scales, generate observed spatial patterns. Large gaps in theory and empirical data in temporal dynamics of metacommunities have hindered progress in our understanding of underlying metacommunity processes that give rise to biodiversity patterns. Fortunately, long-term studies with cross-scale spatial replication can provide a means to gain a deeper understanding of the multiscale processes driving biodiversity patterns in time and space to inform metacommunity theory. The maturation of coordinated research and observation networks, such as the U.S. Long-Term Ecological Research program, provides an opportunity to advance explanation and prediction of biodiversity change with observational and experimental data at spatial and temporal scales greater than any single research group could accomplish. Synthesis of Long Term Ecological Research network community datasets illustrates that many long-term studies with spatial replication present an unutilized empirical resource for advancing spatiotemporal metacommunity research. We identify challenges to synthesizing these data and present recommendations for addressing them with insights about how future monitoring efforts by coordinated research and observation networks might better promote future integration of data across space and time to further the development of metacommunity theory and its applications aimed at improving conservation efforts.

62. Designing flow regimes to support entire river ecosystems
2021 – Frontiers in Ecology and the Environment
Jonathan D. Tonkin, Julian D. Olden, David M. Merritt, Lindsay V. Reynolds, Jane S. Rogosch, David A. Lytle

Overcoming challenges of water scarcity necessitates creative flow management approaches that account for multiple, potentially competing water needs of plants and animals in river ecosystems. Mechanistic multispecies models can guide decision making by evaluating trade-offs associated with flow regimes designed for specific ecosystem outcomes before implementation. We investigated the cross-ecosystem effects of environmental flow regimes designed to benefit focal groups of riparian vegetation, fishes, and invertebrates. The models revealed trade-offs among different designer flow regimes with narrow taxonomic targets, which in some cases caused non-target taxa to become locally extirpated within short (decadal) timespans. By incorporating multiple flow frequencies – from intra-annual-scale pulses to large decadal-scale floods – the simulated natural flow regime enabled balanced, albeit smaller, population sizes across the three ecosystem components: 72% of that achieved by designer flow regimes, on average. Although returning to a natural flow regime may not be possible in highly flow-modified rivers, novel flow regimes must incorporate diverse flood and drought frequencies to accommodate the occasionally conflicting requirements of different taxa at different times.

2020

61. The effects of abiotic and biotic factors on taxonomic and phylogenetic diversity of stream epilithic bacteria around Qiandao Lake
2020 – Aquatic Sciences
Mingjia Li, Jinfu Liu, Jonathan D. Tonkin, Ji Shen, Nengwen Xiao, Jianjun Wang

Stream bacterial communities are shaped by a combination of local and regional processes, such as environmental filtering, biotic interactions and dispersal, but biotic interactions have received comparatively less attention. Here, we investigated stream bacterial alpha and beta diversity within taxonomic and phylogenetic contexts around Qiandao Lake in China. We further examined abiotic and biotic factors on bacterial communities by explicitly considering biotic variables including macroinvertebrate species richness, total cover of periphyton and submerged macrophytes. For alpha and beta diversity, there were consistently high correlations between taxonomic and observed phylogenetic metrics. Taxonomic and phylogenetic diversity could be explained by abiotic and biotic variables, though the former showed a stronger influence. Using a null model to break down the association between species phylogeny and co-occurrence, we found non-significant correlations for alpha and beta diversity between taxonomic and phylogenetic diversity, that is, the standardized effect size of phylogenetic diversity (ses.PD) or Unifrac dissimilarity (ses.Unifrac). Variations in taxonomic and phylogenetic diversity at both alpha and beta levels were mainly explained by pure effect of abiotic variables. Biotic variables, such as macroinvertebrate species richness and total cover of periphyton, significantly explained the variations in ses.PD and ses.Unifrac by 19.4% and 18.9%, respectively. Our findings provide an evidence that biotic variables play a non-negligible role in structuring bacterial communities and help to better understand the potential role of biological interactions across trophic levels in streams.

60. Local contribution to beta diversity is negatively linked with community-wide dispersal capacity in stream invertebrate communities
2020 – Ecological Indicators
Fengqing Li, Jonathan D. Tonkin, Peter Haase

It is increasingly well understood that stream communities are regulated by both local niche and regional dispersal processes, but comprehensive tests of these factors with datasets that cover extensive spatial and temporal scales are rare. Based on 1180 benthic invertebrate community samples from 2005 to 2012 in central low mountain streams of Germany, we tested the hypotheses that: 1) local contribution to beta diversity (LCBD: a measure of the uniqueness of communities) would decline with increasing average community dispersal capacity; and 2) owing to the relatively large spatial extent of the study region, regional dispersal processes would override local niche controls in structuring community composition. We found considerable temporal variation in LCBD and a negative correlation between LCBD and community dispersal capacity. However, no statistically significant correlation between species contribution to beta diversity (SCBD) and species dispersal capacity was observed. The large-scale spatial structure among locations (representative of dispersal limitation) was important in structuring benthic communities. Although much of the variation was explained by the shared effects of local processes and large-scale spatial variables, environmental controls were stronger than regional processes in few cases in the variance partitioning analysis, with the annual mean temperature and mean diurnal range of temperature being the important drivers. Given the highly varied correlates of beta diversity over time, we urge researchers to focus on not only spatial variation in diversity, but also the context of temporal variation.

59. Increasing climate-driven taxonomic homogenization but functional differentiation among river macroinvertebrate assemblages
2020 – Global Change Biology
Théophile L. Mouton, Jonathan D. Tonkin, Fabrice Stephenson, Piet Verburg, Mathieu Floury

Global change is increasing biotic homogenization globally, which modifies the functioning of ecosystems. While tendencies towards taxonomic homogenization in biological communities have been extensively studied, functional homogenization remains an understudied facet of biodiversity. Here, we tested four hypotheses related to long-term changes (1991–2016) in the taxonomic and functional arrangement of freshwater macroinvertebrate assemblages across space and possible drivers of these changes. Using data collected annually at 64 river sites in mainland New Zealand, we related temporal changes in taxonomic and functional spatial {\(\beta\)}-diversity, and the contribution of individual sites to {\(\beta\)}-diversity, to a set of global, regional, catchment and reach-scale environmental descriptors. We observed long-term, mostly climate-induced, temporal trends towards taxonomic homogenization but functional differentiation among macroinvertebrate assemblages. These changes were mainly driven by replacements of species and functional traits among assemblages, rather than nested species loss. In addition, there was no difference between the mean rate of change in the taxonomic and functional facets of {\(\beta\)}-diversity. Climatic processes governed overall population and community changes in these freshwater ecosystems, but were amplified by multiple anthropogenic, topographic and biotic drivers of environmental change, acting widely across the landscape. The functional diversification of communities could potentially provide communities with greater stability, resistance and resilience capacity to environmental change, despite ongoing taxonomic homogenization. Therefore, our study highlights a need to further understand temporal trajectories in both taxonomic and functional components of species communities, which could enable a clearer picture of how biodiversity and ecosystems will respond to future global changes.

58. Conservation of freshwater macroinvertebrate biodiversity in tropical regions
2020 – Aquatic Conservation: Marine and Freshwater Ecosystems
S. Sundar, Jani Heino, Fabio de Oliveira Roque, John P. Simaika, Adriano S. Melo, Jonathan D. Tonkin, Davidson {Gomes Nogueira}, Daniel Paiva Silva

Motivated by recent global initiatives for biodiversity conservation and restoration, this article reviews the gaps in our understanding of, and the challenges facing, freshwater macroinvertebrate biodiversity and conservation in tropical regions. This study revealed a lack of adequate taxonomic, phylogenetic, and ecological information for most macroinvertebrate groups, and consequently there are large-scale knowledge gaps regarding the response of macroinvertebrate diversity to potential climate change and other human impacts in tropical regions. We propose ideas to reduce the impact of key drivers of declines in macroinvertebrate biodiversity, including habitat degradation and loss, hydrological alteration, overexploitation, invasive species, pollution, and the multiple impacts of climate change. The review also provides recommendations to enhance conservation planning in these systems (as well as providing clear management plans at local, regional, and national levels), integrated catchment management, the formulation of regulatory measures, the understanding of the determinants of macroinvertebrate diversity across multiple scales and taxonomic groups, and the collaboration between researchers and conservation professionals. It is suggested that the integrated use of macroinvertebrate biodiversity information in biomonitoring can improve ecosystem management. This goal can be facilitated in part by conservation psychology, marketing, and the use of the media and the Internet.

2019

57. Moderate warming over the past 25 years has already reorganized stream invertebrate communities
2019 – Science of The Total Environment
Peter Haase, Francesca Pilotto, Fengqing Li, Andrea Sundermann, Armin W. Lorenz, Jonathan D. Tonkin, Stefan Stoll

Climate warming often results in species range shifts, biodiversity loss and accumulated climatic debts of biota (i.e. slower changes in biota than in temperature). Here, we analyzed the changes in community composition and temperature signature of stream invertebrate communities over 25,years (1990–2014), based on a large set of samples (n,=,3782) over large elevation, latitudinal and longitudinal gradients in central Europe. Although warming was moderate (average 0.5,{\(^\circ\)}C), we found a strong reorganization of stream invertebrate communities. Total abundance (+35.9%) and richness (+39.2%) significantly increased. The share of abundance (TA) and taxonomic richness (TR) of warm-dwelling taxa (TA: +73.2%; TR: +60.2%) and medium-temperature-dwelling taxa (TA: +0.4%; TR: +5.8%) increased too, while cold-dwelling taxa declined (TA: -61.5%; TR: -47.3%). The community temperature index, representing the temperature signature of stream invertebrate communities, increased at a similar pace to physical temperature, indicating a thermophilization of the communities and, for the first time, no climatic debt. The strongest changes occurred along the altitudinal gradient, suggesting that stream invertebrates use the spatial configuration of river networks to track their temperature niche uphill. Yet, this may soon come to an end due to the summit trap effect. Our results indicate an ongoing process of replacement of cold-adapted species by thermophilic species at only 0.5,{\(^\circ\)}C warming, which is particularly alarming in the light of the more drastic climate warming projected for coming decades.

56. Reintroduction of freshwater macroinvertebrates: challenges and opportunities: Reintroduction of freshwater macroinvertebrates
2019 – Biological Reviews
Jonas Jourdan, Martin Plath, Jonathan D. Tonkin, Maria Ceylan, Arlena C. Dumeier, Georg Gellert, Wolfram Graf, Charles P. Hawkins, Ellen Kiel, Armin W. Lorenz, Christoph D. Matthaei, Piet F. M. Verdonschot, Ralf C. M. Verdonschot, Peter Haase

Species reintroductions – the translocation of individuals to areas in which a species has been extirpated with the aim of re-establishing a self-sustaining population – have become a widespread practice in conservation biology. Reintroduction projects have tended to focus on terrestrial vertebrates and, to a lesser extent, fishes. Much less effort has been devoted to the reintroduction of invertebrates into restored freshwater habitats. Yet, reintroductions may improve restoration outcomes in regions where impoverished regional species pools limit the self-recolonisation of restored freshwaters. We review the available literature on macroinvertebrate reintroductions, focusing on identifying the intrinsic and extrinsic factors that determine their success or failure. Our study reveals that freshwater macroinvertebrate reintroductions remain rare, are often published in the grey literature and, of the attempts made, approximately one-third fail. We identify life-cycle complexity and remaining stressors as the two factors most likely to affect reintroduction success, illustrating the unique challenges of freshwater macroinvertebrate reintroductions. Consideration of these factors by managers during the planning process and proper documentation – even if a project fails – may increase the likelihood of successful outcomes in future reintroduction attempts of freshwater macroinvertebrates.

55. Diverging response patterns of terrestrial and aquatic species to hydromorphological restoration
2019 – Conservation Biology
Francesca Pilotto, Jonathan D. Tonkin, Kathrin Januschke, Armin W. Lorenz, Jonas Jourdan, Andrea Sundermann, Daniel Hering, Stefan Stoll, Peter Haase

Although experiences with ecological restoration continue to accumulate, the effectiveness of restoration for biota remains debated. We complemented a traditional taxonomic analysis approach with information on 56 species traits to uncover the responses of 3 aquatic (fish, macroinvertebrates, macrophytes) and 2 terrestrial (carabid beetles, floodplain vegetation) biotic groups to 43 hydromorphological river restoration projects in Germany. All taxonomic groups responded positively to restoration, as shown by increased taxonomic richness (10–164%) and trait diversity (habitat, dispersal and mobility, size, form, life history, and feeding groups) (15–120%). Responses, however, were stronger for terrestrial than aquatic biota, and, contrary to our expectation, taxonomic responses were stronger than those of traits. Nevertheless, trait analysis provided mechanistic insights into the drivers of community change following restoration. Trait analysis for terrestrial biota indicated restoration success was likely enhanced by lateral connectivity and reestablishment of dynamic processes in the floodplain. The weaker response of aquatic biota suggests recovery was hindered by the persistence of stressors in the aquatic environment, such as degraded water quality, dispersal constraints, and insufficient hydromorphological change. Therefore, river restoration requires combined localand regional-scale approaches to maximize the response of both aquatic and terrestrial organisms. Due to the contrasting responses of aquatic and terrestrial biota, the planning and assessment of river restoration outcomes should consider effects on both components of riverine landscapes.

54. Increasing drought favors nonnative fishes in a dryland river: evidence from a multispecies demographic model
2019 – Ecosphere
Jane S. Rogosch, Jonathan D. Tonkin, David A. Lytle, David M. Merritt, Lindsay V. Reynolds, Julian D. Olden

Understanding how novel biological assemblages are structured in relation to dynamic environmental regimes remains a central challenge in ecology. Demographic approaches to modeling species assemblages show promise because they seek to represent fundamental relationships between population dynamics and environmental conditions. In dryland rivers, rapidly changing climate conditions have shifted drought and flooding regimes with implications for fish communities. Our goals were to (1) develop a mechanistic multispecies demographic model that links native and nonnative species with river flow regimes, and (2) evaluate demographic responses in population and community structure to changing flow regimes. Each fish species was represented by a stage-structured matrix, and species were coupled together into a multispecies framework through density-dependent relationships in reproduction. Then, community dynamics were simulated through time using annual flow events classified from gaged streamflow data. We parameterized the model with vital rates and flow–response relationships for a community of native and nonnative fishes using literature-derived values. We applied the simulation model to the Verde River (Arizona, USA), a major tributary within the Colorado River Basin, for the past half century (1964–2017). Model validation revealed a match between model projections and relative abundance trends observed in a long-term fish monitoring dataset (1994–2008). At the beginning of the validation period (1994), model and survey observations showed that native species comprised approximately 80% of total abundance. Model projections beyond the survey data (2008–2017) predicted a shift from a native dominant to a nonnative dominant assemblage, coinciding with increasing drought frequency. Trade-offs between native and nonnative species dominance emerged from differences in mortality in response to the changing sequence of major flow events including spring floods, summer high flows, and droughts. In conclusion, the demographic approach presented here provides a flexible modeling framework that is readily applied to other stream systems and species by adjusting or transferring, when appropriate, species vital rates and flow-event thresholds.

53. Global patterns and drivers of ecosystem functioning in rivers and riparian zones
2019 – Science Advances
Scott D. Tiegs, David M. Costello, Mark W. Isken, Guy Woodward, Peter B. McIntyre, Mark O. Gessner, Eric Chauvet, Natalie A. Griffiths, Alex S. Flecker, Vicenç Acuña, Ricardo Albariño, Daniel C. Allen, Cecilia Alonso, Patricio Andino, Clay Arango, Jukka Aroviita, Marcus V. M. Barbosa, Leon A. Barmuta, Colden V. Baxter, Thomas D. C. Bell, Brent Bellinger, Luz Boyero, Lee E. Brown, Andreas Bruder, Denise A. Bruesewitz, Francis J. Burdon, Marcos Callisto, Cristina Canhoto, Krista A. Capps, María M. Castillo, Joanne Clapcott, Fanny Colas, Checo Colón-Gaud, Julien Cornut, Verónica Crespo-Pérez, Wyatt F. Cross, Joseph M. Culp, Michael Danger, Olivier Dangles, Elvira {de Eyto}, Alison M. Derry, Veronica Díaz Villanueva, Michael M. Douglas, Arturo Elosegi, Andrea C. Encalada, Sally Entrekin, Rodrigo Espinosa, Diana Ethaiya, Verónica Ferreira, Carmen Ferriol, Kyla M. Flanagan, Tadeusz Fleituch, Jennifer J. {Follstad Shah}, André {Frainer Barbosa}, Nikolai Friberg, Paul C. Frost, Erica A. Garcia, Liliana {García Lago}, Pavel Ernesto {García Soto}, Sudeep Ghate, Darren P. Giling, Alan Gilmer, José Francisco Gonçalves, Rosario Karina Gonzales, Manuel A. S. Graça, Mike Grace, Hans-Peter Grossart, François Guérold, Vlad Gulis, Luiz U. Hepp, Scott Higgins, Takuo Hishi, Joseph Huddart, John Hudson, Samantha Imberger, Carlos Iñiguez-Armijos, Tomoya Iwata, David J. Janetski, Eleanor Jennings, Andrea E. Kirkwood, Aaron A. Koning, Sarian Kosten, Kevin A. Kuehn, Hjalmar Laudon, Peter R. Leavitt, Aurea L. {Lemes da Silva}, Shawn J. Leroux, Carri J. LeRoy, Peter J. Lisi, Richard MacKenzie, Amy M. Marcarelli, Frank O. Masese, Brendan G. McKie, Adriana {Oliveira Medeiros}, Kristian Meissner, Marko Miliša, Shailendra Mishra, Yo Miyake, Ashley Moerke, Shorok Mombrikotb, Rob Mooney, Tim Moulton, Timo Muotka, Junjiro N. Negishi, Vinicius Neres-Lima, Mika L. Nieminen, Jorge Nimptsch, Jakub Ondruch, Riku Paavola, Isabel Pardo, Christopher J. Patrick, Edwin T. H. M. Peeters, Jesus Pozo, Catherine Pringle, Aaron Prussian, Estefania Quenta, Antonio Quesada, Brian Reid, John S. Richardson, Anna Rigosi, José Rincón, Geta Rî{ş}noveanu, Christopher T. Robinson, Lorena Rodríguez-Gallego, Todd V. Royer, James A. Rusak, Anna C. Santamans, Géza B. Selmeczy, Gelas Simiyu, Agnija Skuja, Jerzy Smykla, Kandikere R. Sridhar, Ryan Sponseller, Aaron Stoler, Christopher M. Swan, David Szlag, Franco {Teixeira-de Mello}, Jonathan D. Tonkin, Sari Uusheimo, Allison M. Veach, Sirje Vilbaste, Lena B. M. Vought, Chiao-Ping Wang, Jackson R. Webster, Paul B. Wilson, Stefan Woelfl, Marguerite A. Xenopoulos, Adam G. Yates, Chihiro Yoshimura, Catherine M. Yule, Yixin X. Zhang, Jacob A. Zwart

River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth’s biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented next-generation biomonitoring by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale.

52. Prepare river ecosystems for an uncertain future
2019 – Nature
Jonathan D. Tonkin, N. LeRoy Poff, Nick R. Bond, Avril Horne, David. M. Merritt, Lindsay V. Reynolds, Julian D. Olden, Albert Ruhi, David A. Lytle

As the climate warms, we can’t restore waterways to pristine condition, but models can predict potential changes, argue Jonathan D. Tonkin, N. LeRoy Poff and colleagues.

51. The three Rs of river ecosystem resilience: Resources, recruitment, and refugia: The three Rs of river resilience: Resources, Recruitment and Refugia
2019 – River Research and Applications
Kris {Van Looy}, Jonathan D. Tonkin, Mathieu Floury, Catherine Leigh, Janne Soininen, Stefano Larsen, Jani Heino, N. {LeRoy Poff}, Michael Delong, Sonja C. Jähnig, Thibault Datry, Núria Bonada, Juliette Rosebery, Aurélien Jamoneau, Steve J. Ormerod, Kevin J. Collier, Christian Wolter

Resilience in river ecosystems requires that organisms must persist in the face of highly dynamic hydrological and geomorphological variations. Disturbance events such as floods and droughts are postulated to shape life history traits that support resilience, but river management and conservation would benefit from greater understanding of the emergent effects in communities of river organisms.

50. Urbanization impacts the physicochemical characteristics and abundance of fecal markers and bacterial pathogens in surface water
2019 – International Journal of Environmental Research and Public Health
Tianma Yuan, Kiran Kumar Vadde, Jonathan D. Tonkin, Jianjun Wang, Jing Lu, Zimeng Zhang, Yixin Zhang, Alan J. McCarthy, Raju Sekar

Urbanization is increasing worldwide and is happening at a rapid rate in China in line with economic development. Urbanization can lead to major changes in freshwater environments through multiple chemical and microbial contaminants. We assessed the impact of urbanization on physicochemical characteristics and microbial loading in canals in Suzhou, a city that has experienced rapid urbanization in recent decades. Nine sampling locations covering three urban intensity classes (high, medium and low) in Suzhou were selected for field studies and three locations in Huangshan (natural reserve) were included as pristine control locations. Water samples were collected for physicochemical, microbiological and molecular analyses. Compared to medium and low urbanization sites, there were statistically significant higher levels of nutrients and total and thermotolerant coliforms (or fecal coliforms) in highly urbanized locations. The effect of urbanization was also apparent in the abundances of human-associated fecal markers and bacterial pathogens in water samples from highly urbanized locations. These results correlated well with land use types and anthropogenic activities at the sampling sites. The overall results indicate that urbanization negatively impacts water quality, providing high levels of nutrients and a microbial load that includes fecal markers and pathogens.

2018

49. Assessing phytoplankton composition and structure within micro-estuaries and micro-outlets: a community analysis approach
2018 – Hydrobiologia
Tatenda Dalu, Mandla L. Magoro, Jonathan D. Tonkin, Lucienne R. D. Human, Renzo Perissinotto, Shaun H. P. Deyzel, Janine B. Adams, Alan K. Whitfield

Micro-estuaries and micro-outlets represent small coastal waterbodies that differ in their relative salinity and size, with the former being larger, more saline (mesohaline versus oligohaline), and exchanging with the sea more often than the latter. There are thousands of these waterbodies along the world’s coastline, yet few of these very small systems have been identified and studied. We investigated systematic differences between micro-estuaries and micro-outlets in terms of phytoplankton community composition, including spatio-temporal variation in both community structure and biomass (chlorophyll-a). A multivariate analysis was used to assess differences in environmental variables, biomass and phytoplankton community composition across four seasons and the two waterbody types. A total of 260 (63 families) and 244 (74 families) phytoplankton taxa were identified within the micro-estuaries and micro-outlets, respectively. Nano- and picoplankton were the dominant groups in micro-estuaries, and pico- and microplankton in micro-outlets. Micro-estuaries were rich in phytoplankton taxa representative of marine, estuarine and freshwater conditions, with a successional sequence in dominance evident, from Chlorophyta during winter to Bacillariophyta in spring and Cyanophyta in summer. By contrast, micro-outlets were mostly dominated by freshwater taxa, with Chlorophyta remaining the dominant group across all four seasons. Higher phytoplankton biomass was recorded during the winter when increased nutrients were available following catchment flooding. Seasonal switching in phytoplankton was reflected not only in changing dominance patterns in both habitat types but also in complete replacement of some species in micro-outlets, despite Chlorophyta remaining dominant. Such temporal turnover, which is often accompanied by predictable seasonal changes in environmental conditions, can promote overall species richness by allowing more taxa to coexist in a single environment through temporal niche segregation.

48. The next generation of site-based long-term ecological monitoring: Linking essential biodiversity variables and ecosystem integrity
2018 – Science of The Total Environment
Peter Haase, Jonathan D. Tonkin, Stefan Stoll, Benjamin Burkhard, Mark Frenzel, Ilse R. Geijzendorffer, Christoph Häuser, Stefan Klotz, Ingolf Kühn, William H. McDowell, Michael Mirtl, Felix Müller, Martin Musche, Johannes Penner, Steffen Zacharias, Dirk S. Schmeller

Global change effects on biodiversity and human wellbeing call for improved long-term environmental data as a basis for science, policy and decision making, including increased interoperability, multifunctionality, and harmonization. Based on the example of two global initiatives, the International Long-Term Ecological Research (ILTER) network and the Group on Earth Observations Biodiversity Observation Network (GEO BON), we propose merging the frameworks behind these initiatives, namely ecosystem integrity and essential biodiversity variables, to serve as an improved guideline for future site-based long-term research and monitoring in terrestrial, freshwater and coastal ecosystems. We derive a list of specific recommendations of what and how to measure at a monitoring site and call for an integration of sites into co-located site networks across individual monitoring initiatives, and centered on ecosystems. This facilitates the generation of linked comprehensive ecosystem monitoring data, supports synergies in the use of costly infrastructures, fosters cross-initiative research and provides a template for collaboration beyond the ILTER and GEO BON communities.

47. Effects of changing climate on European stream invertebrate communities: A long-term data analysis
2018 – Science of The Total Environment
Jonas Jourdan, Robert B. O’Hara, Roberta Bottarin, Kaisa-Leena Huttunen, Mathias Kuemmerlen, Don Monteith, Timo Muotka, D=avis Ozoli, Riku Paavola, Francesca Pilotto, Gunta Springe, Agnija Skuja, Andrea Sundermann, Jonathan D. Tonkin, Peter Haase

Long-term observations on riverine benthic invertebrate communities enable assessments of the potential impacts of global change on stream ecosystems. Besides increasing average temperatures, many studies predict greater temperature extremes and intense precipitation events as a consequence of climate change. In this study we examined long-term observation data (10–32 years) of 26 streams and rivers from four ecoregions in the European Long-Term Ecological Research (LTER) network, to investigate invertebrate community responses to changing climatic conditions. We used functional trait and multi-taxonomic analyses and combined examinations of general long-term changes in communities with detailed analyses of the impact of different climatic drivers (i.e., various temperature and precipitation variables) by focusing on the response of communities to climatic conditions of the previous year. Taxa and ecoregions differed substantially in their response to climate change conditions. We did not observe any trend of changes in total taxonomic richness or overall abundance over time or with increasing temperatures, which reflects a compensatory turnover in the composition of communities; sensitive Plecoptera decreased in response to warmer years and Ephemeroptera increased in northern regions. Invasive species increased with an increasing number of extreme days which also caused an apparent upstream community movement. The observed changes in functional feeding group diversity indicate that climate change may be associated with changes in trophic interactions within aquatic food webs. These findings highlight the vulnerability of riverine ecosystems to climate change and emphasize the need to further explore the interactive effects of climate change variables with other local stressors to develop appropriate conservation measures.

46. Dispersal capacity and broad-scale landscape structure shape benthic invertebrate communities along stream networks
2018 – Limnologica
Fengqing Li, Jonathan D. Tonkin, Peter Haase

Dispersal is a fundamental trait influencing species{} distribution patterns and metacommunity structure. Yet, for stream communities it remains unclear how communities differ in dispersal capacity. Due to the dendritic network structure of streams and the greater spatial variability in environmental conditions in headwaters than in mainstems, we asked three main questions: 1) Do benthic invertebrates inhabiting headwaters have lower community-wide dispersal capacities (DCc) on average than those living in mainstems? 2) In turn, does the degree of community dissimilarity among sites differ between the different locations in the river network? 3) Are these differences more pronounced in highland streams compared to lowland streams as a consequence of major landscape features (i.e. mountains)? To examine these questions, we compiled 1466 benthic invertebrate samples across the southern highland and northern lowland areas of Germany. Results showed that overall DCc increased with stream size in both highland and lowland streams. In highland streams, higher DCc in mainstems was associated with more homogeneous communities compared to headwater communities. However, this pattern did not occur in lowland streams. This suggests that both dispersal capacity and landscape structure interact to determine community structure in these networks. Our results therefore stress the importance of considering dispersal traits and landscape features, as well as habitat control (or environmental filtering) to better understand (meta-) community structure across various landscape types.

45. Flow regime alteration degrades ecological networks in riparian ecosystems
2018 – Nature Ecology & Evolution
Jonathan D. Tonkin, David. M. Merritt, Julian D. Olden, Lindsay V. Reynolds, David A. Lytle

Riverine ecosystems are governed by patterns of temporal variation in river flows. This dynamism will change due to climate change and the near-ubiquitous human control of river flows globally, which may have severe effects on species distributions and interactions. We employed a combination of population modelling and network theory to explore the consequences of possible flow regime futures on riparian plant communities, including scenarios of increased drought, flooding and flow homogenization (removal of flow variability). We found that even slight modifications to the historic natural flow regime had significant consequences for the structure of riparian plant networks. Networks of emergent interactions between plant guilds were most connected at the natural flow regime and became simplified with increasing flow alteration. The most influential component of flow alteration was flood reduction, with drought and flow homogenization both having greater simplifying community-wide consequences than increased flooding. These findings suggest that maintaining floods under future climates will be needed to overcome the negative long-term consequences of flow modification on riverine ecosystems.

44. Do latitudinal gradients exist in New Zealand stream invertebrate metacommunities?
2018 – PeerJ
Jonathan D. Tonkin, Russell G. Death, Timo Muotka, Anna Astorga, David A. Lytle

That biodiversity declines with latitude is well known, but whether a metacommunity process is behind this gradient has received limited attention. We tested the hypothesis that dispersal limitation is progressively replaced by mass effects with increasing latitude, along with a series of related hypotheses. We explored these hypotheses by examining metacommunity structure in stream invertebrate metacommunities spanning the length of New Zealand’s two largest islands ({\(\sim\)}1,300 km), further disentangling the role of dispersal by deconstructing assemblages into strong and weak dispersers. Given the highly dynamic nature of New Zealand streams, our alternative hypothesis was that these systems are so unpredictable (at different stages of post-flood succession) that metacommunity structure is highly context dependent from region to region. We rejected our primary hypotheses, pinning this lack of fit on the strong unpredictability of New Zealand’s dynamic stream ecosystems and fauna that has evolved to cope with these conditions. While local community structure turned over along this latitudinal gradient, metacommunity structure was highly context dependent and dispersal traits did not elucidate patterns. Moreover, the emergent metacommunity types exhibited no trends, nor did the important environmental variables. These results provide a cautionary tale for examining singular metacommunities. The considerable level of unexplained contingency suggests that any inferences drawn from one-off snapshot sampling may be misleading and further points to the need for more studies on temporal dynamics of metacommunity processes.

43. Metacommunities in river networks: The importance of network structure and connectivity on patterns and processes
2018 – Freshwater Biology
Jonathan D. Tonkin, Jani Heino, Florian Altermatt

Rivers are spatially organised into hierarchic dendritic networks. This unique physical structure and the associated directionality of physical flows set them apart from most other environments by regulating the dispersal of resident biota and therefore the distribution of biodiversity. The aim of this special issue is to highlight the importance of the river network on structuring biodiversity, particularly through metacommunity dynamics and associated dispersal processes. The issue covers a wide range of topics, including disease spread, nutrient uptake, trophic dynamics, effects of anthropogenic stressors and the joint roles of dispersal and environmental filtering. Contributions employ a broad range of approaches, including field and laboratory experiments, modelling, population genetics and conceptual synthesis. Although these studies represent just a sample of the research that is being performed on biodiversity and metacommunity dynamics in river networks, several important findings have emerged; a common theme being that the structure of the network and spatial dynamics clearly influence the dynamics of populations and communities, and their functions. By taking a broad taxonomic focus (from diatoms and protists to fish), and spanning a large geographic gradient (from the tropics to the subarctic), this special issue provides a broad look at the dynamics that occur in river networks relating to their unique makeup. We hope that this selection of studies spurs additional research on these interesting, globally important, yet severely threatened ecological systems.

42. The role of dispersal in river network metacommunities: Patterns, processes, and pathways
2018 – Freshwater Biology
Jonathan D. Tonkin, Florian Altermatt, Debra S. Finn, Jani Heino, Julian D. Olden, Steffen U. Pauls, David. A. Lytle

River networks are hierarchical dendritic habitats embedded within the terrestrial landscape, with varying connectivity between sites depending on their positions along the network. This physical organisation influences the dispersal of organisms, which ultimately affects metacommunity dynamics and biodiversity patterns. We provide a conceptual synthesis of the role of river networks in structuring metacommunities in relation to dispersal processes in riverine ecosystems. We explore where the river network best explains observed metacommunity structure compared to other measurements of physical connectivity. We mostly focus on invertebrates, but also consider other taxonomic groups, including microbes, fishes, plants, and amphibians. Synthesising studies that compared multiple spatial distance metrics, we found that the importance of the river network itself in explaining metacommunity patterns depended on a variety of factors, including dispersal mode (aquatic versus aerial versus terrestrial) and landscape type (arid versus mesic), as well as location-specific factors, such as network connectivity, land use, topographic heterogeneity, and biotic interactions. The river network appears to be less important for strong aerial dispersers and insects in arid systems than for other groups and biomes, but there is considerable variability. Borrowing from other literature, particularly landscape genetics, we developed a conceptual model that predicts that the explanatory power of the river network peaks in mesic systems for obligate aquatic dispersers. We propose directions of future avenues of research, including the use of manipulative field and laboratory experiments that test metacommunity theory in river networks. While field and laboratory experiments have their own benefits and drawbacks (e.g. reality, control, cost), both are powerful approaches for understanding the mechanisms structuring metacommunities, by teasing apart dispersal and niche-related factors. Finally, improving our knowledge of dispersal in river networks will benefit from expanding the breadth of cost-distance modelling to better infer dispersal from observational data; an improved understanding of life-history strategies rather than relying on independent traits; exploring individual-level variation in dispersal through detailed genetic studies; detailed studies on fine-scale environmental (e.g. daily hydrology) and organismal spatiotemporal variability; and synthesising comparative, experimental, and theoretical work. Expanding in these areas will help to push the current state of the science from a largely pattern-detection mode into a new phase of more mechanistically driven research.

41. Unlocking biodiversity data: Prioritization and filling the gaps in biodiversity observation data in Europe
2018 – Biological Conservation
Florian T. Wetzel, Heather C. Bingham, Quentin Groom, Peter Haase, Urmas Kõljalg, Michael Kuhlmann, Corinne S. Martin, Lyubomir Penev, Tim Robertson, Hannu Saarenmaa, Dirk S. Schmeller, Stefan Stoll, Jonathan D. Tonkin, Christoph L. Häuser

Large quantities of biodiversity data are required to assess the current status of species, to identify drivers of population and distributional change, and to predict changes to biodiversity under future scenarios. Nevertheless, currently-available data are often not well-suited to these purposes. To highlight existing gaps, we assess the availability of species observation data in Europe, their geographic and temporal range, and their quality. We do so by reviewing the most relevant sources for European biodiversity observation data, and identifying important barriers to filling gaps. We suggest strategies, tools and frameworks to continue to fill these gaps, in addition to producing data suitable for generating Essential Biodiversity Variables (EBVs). Our review of data sources shows that only around a third of data-providers provide unrestricted data access. Particularly large geographic gaps exist in Eastern European countries and many datasets are not suitable for generating EBVs due to the absence of long-term data. We highlight examples built on recent experiences from large data integrators, publishers and networks that help to efficiently improve data availability, adopt open science principles and close existing data gaps. Future strategies must urgently consider the needs of relevant data stakeholders, particularly science- and policy-related needs, and provide incentives for data-providers. Hence, sustainable, longterm infrastructures and a European biodiversity network are needed to provide such efficient workflows, incentives for data-provision and tools.

2017

40. Assessing drivers of benthic macroinvertebrate community structure in African highland streams: An exploration using multivariate analysis
2017 – Science of The Total Environment
Tatenda Dalu, Ryan J. Wasserman, Jonathan D. Tonkin, Mhairi E. Alexander, Mwazvita T.B. Dalu, Samuel N. Motitsoe, Kwanele I. Manungo, Onias Bepe, Timothy Dube

Understanding the drivers of community structure is fundamental for adequately managing ecosystems under global change. Here we used a large dataset of eighty-four headwater stream sites in three catchments in the Eastern Highlands of Zimbabwe, which represent a variety of abiotic conditions and levels of impairment, to examine the drivers of benthic macroinvertebrate community structure. We focused our assessment on macroinvertebrate family level community composition and functional feeding group classifications. Taxonomic richness was weakly positively correlated with ammonium, phosphates and pH, and weakly negatively correlated with detrital cover and dissolved oxygen. Measured abiotic variables, however, had limited influence on both macroinvertebrate diversity and functional feeding group structure, with the exception of ammonium, channel width and phosphates. This reflected the fact that many macroinvertebrate families and functional feeding guilds were well represented across a broad range of habitats. Predatory macroinvertebrates were relatively abundant, with collector-filterers having the lowest relative abundances. The findings of the study suggest that for certain ecological questions, a more detailed taxonomic resolution may be required to adequately understand the ecology of aquatic macroinvertebrates within river systems. We further recommend management and conservation initiatives on the Save River system, which showed significant impact from catchment developmental pressures, such as urbanisation, agriculture and illegal mining.

39. Water or sediment? Partitioning the role of water column and sediment chemistry as drivers of macroinvertebrate communities in an austral South African stream
2017 – Science of The Total Environment
Tatenda Dalu, Ryan J. Wasserman, Jonathan D. Tonkin, Tongayi Mwedzi, Mandla L. Magoro, Olaf L.F. Weyl

Water pollution is a critical management issue, with many rivers and streams draining urban areas being polluted by the disposal of untreated solid waste and wastewater discharge, storm water and agricultural runoff. This has implications for biodiversity, and many rivers in the developing world are now considered compromised. We investigated benthic macroinvertebrate community structure and composition in relation to physico-chemical conditions of the water column and sediments. The study was conducted in an Austral catchment subject to both urban and agricultural pollutants in two different seasons. We assessed whether sediment characteristics were more important drivers of macroinvertebrate community composition than water column characteristics. We expected clear differences in macroinvertebrate community composition and in the associated community metrics due to distinct flow conditions between the two seasons. A combination of multivariate analyses (canonical correspondence analysis (CCA)) and biological indicator analysis were used to examine these patterns. Chironomidae was the most abundant family ({\(>\)} 60%) in the upper mainstem river and stream sites. Stream sites were positively associated with CCA axis 2, being characterised by high turbidity and lower pH, salinity, phosphate concentration, channel width and canopy cover. Canopy cover, channel width, substrate embeddedness, phosphate concentration, pH, salinity and turbidity all had a significant effect on macroinvertebrate community composition. Using CCA variation partitioning, water quality was, however, a better predictor of benthic macroinvertebrate composition than sediment chemical conditions. Furthermore, our results suggest that seasonality had little effect on structuring benthic macroinvertebrate communities in this south-eastern zone of South Africa, despite clear changes in sediment chemistry. This likely reflects the relative lack of major variability in water chemistry compared to sediment chemistry between seasons and the relatively muted variability in precipitation between seasons than the more classic Austral temperate climates.

38. Characterizing fish responses to a river restoration over 21 years based on species’ traits: Fish Responses to River Restoration
2017 – Conservation Biology
Stefanie Höckendorff, Jonathan D. Tonkin, Peter Haase, Margret Bunzel-Drüke, Olaf Zimball, Matthias Scharf, Stefan Stoll

Understanding restoration effectiveness is often impaired by a lack of high-quality, long-term monitoring data and, to date, few researchers have used species’ trait information to gain insight into the processes that drive the reaction of fish communities to restoration. We examined fish-community responses with a highly resolved data set from 21 consecutive years of electrofishing (4 years prerestoration and 17 years postrestoration) at multiple restored and unrestored reaches from a river restoration project on the Lippe River, Germany. Fish abundance peaked in the third year after the restoration; abundance was 6 times higher than before the restoration. After 5–7 years, species richness and abundance stabilized at 2 and 3.5 times higher levels relative to the prerestoration level, respectively. However, interannual variability of species richness and abundance remained considerable, illustrating the challenge of reliably assessing restoration outcomes based on data from individual samplings, especially in the first years following restoration. Life-history and reproduction-related traits best explained differences in species’ responses to restoration. Opportunistic short-lived species with early female maturity and multiple spawning runs per year exhibited the strongest increase in abundance, which reflected their ability to rapidly colonize new habitats. These often small-bodied and fusiform fishes typically live in dynamic and ephemeral instream and floodplain areas that river-habitat restorations often aim to create, and in this case their increases in abundance indicated successful restoration. Our results suggest that a greater consideration of species’ traits may enhance the causal understanding of community processes and the coupling of restoration to functional ecology. Trait-based assessments of restoration outcomes would furthermore allow for easier transfer of knowledge across biogeographic borders than studies based on taxonomy.

37. Severity multipliers as a methodology to explore potential effects of climate change on stream bioassessment programs
2017 – Water
Sonja Jähnig, Jonathan D. Tonkin, Maria Gies, Sami Domisch, Daniel Hering, Peter Haase

Given the scientific consensus that climate change is impacting biodiversity, estimates of future climate change effects on stream communities and assessments of potential biases are necessary. Here, we propose a simple technique to approximate changes in invertebrate and fish biomonitoring results. Taxa lists for 60 (invertebrate) and 52 (fish) sites were each modified by 10 multipliers as stepwise 5% or 10% changes in abundances to simulate potential climate-change severity, reflecting increasing climate change effects. These 10 multipliers were based on the stream zonation preference for invertebrates and the Fish Region Index (FRI) values for fish, both reflecting the longitudinal gradient present in river ecosystems. The original and modified taxa lists were analyzed using the standard assessment software for the particular group, followed by analysis of key biomonitoring metrics. For invertebrates, our simulations affected small good quality streams more often negatively while large poor mountain streams showed a tendency to improve. Forty percent of the invertebrate data sites showed a change in the final ecological assessment class when using the multipliers, with the poor quality sites changing more often. For fish, metric changes were variable, but the FRI ratio showed mostly positive responses, i.e., a shift in FRI towards downstream communities. The results are discussed as an example that facilitates the interpretation of potential climate-change effects with varying severity. Further, we discuss the simplified approach and implications for assessment from climate change induced range shifts.

36. Linking river flow regimes to riparian plant guilds: a community-wide modeling approach
2017 – Ecological Applications
David A. Lytle, David M. Merritt, Jonathan D. Tonkin, Julian D. Olden, Lindsay V. Reynolds

Modeling riparian plant dynamics along rivers is complicated by the fact that plants have different edaphic and hydrologic requirements at different life stages. With intensifying human demands for water and continued human alteration of rivers, there is a growing need for predicting responses of vegetation to flow alteration, including responses related to climate change and river flow management. We developed a coupled structured population model that combines stage-s-pecific responses of plant guilds with specific attributes of river hydrologic regime. The model uses information on the vital rates of guilds as they relate to different hydrologic conditions (flood, drought, and baseflow), but deliberately omits biotic interactions from the structure (interaction neutral). Our intent was to (1) consolidate key vital rates concerning plant population dynamics and to incorporate these data into a quantitative framework, (2) determine whether complex plant stand dynamics, including biotic interactions, can be predicted from basic vital rates and river hydrology, and (3) project how altered flow regimes might affect riparian communities. We illustrated the approach using five flow-- response guilds that encompass much of the river floodplain community: hydroriparian tree, xeroriparian shrub, hydroriparian shrub, mesoriparian meadow, and desert shrub. We also developed novel network-b- ased tools for predicting community-w- ide effects of climate-d- riven shifts and deliberately altered flow regimes. The model recovered known patterns of hydroriparian tree vs. xeroriparian shrub dominance, including the relative proportion of these two guilds as a function of river flow modification. By simulating flow alteration scenarios ranging from increased drought to shifts in flood timing, the model predicted that mature hydroriparian forest should be most abundant near the observed natural flow regime. Multiguild sensitivity analysis identified substantial network connectivity (many connected nodes) and biotic linkage (strong pairwise connections between nodes) under natural flow regime conditions. Both connectivity and linkage were substantially reduced under drought and other flow-- alteration scenarios, suggesting that community structure is destabilized under such conditions. This structured population modeling approach provides a useful tool for understanding the community-w- ide effects of altered flow regimes due to climate change and management actions that influence river flow regime.

35. High mortality and enhanced recovery: modelling the countervailing effects of disturbance on population dynamics
2017 – Ecology Letters
Laura E. McMullen, Patrick {De Leenheer}, Jonathan D. Tonkin, David A. Lytle

Disturbances cause high mortality in populations while simultaneously enhancing population growth by improving habitats. These countervailing effects make it difficult to predict population dynamics following disturbance events. To address this challenge, we derived a novel form of the logistic growth equation that permits time-varying carrying capacity and growth rate. We combined this equation with concepts drawn from disturbance ecology to create a general model for population dynamics in disturbance-prone systems. A river flooding example using three insect species (a fast life-cycle mayfly, a slow life-cycle dragonfly and an ostracod) found optimal tradeoffs between disturbance frequency vs. magnitude and a close fit to empirical data in 62% of cases. A savanna fire analysis identified fire frequencies of 3–4 years that maximised population size of a perennial grass. The model shows promise for predicting population dynamics after multiple disturbance events and for management of river flows and fire regimes.

34. Effects of Chaetogaster limnaei limnaei (Oligochaeta, Tubificidae) on freshwater snail communities
2017 – Hydrobiologia
Stefan Stoll, Nico Hormel, Denise Früh, Jonathan D. Tonkin

From laboratory studies, the relationship between the oligochaete Chaetogaster limnaei limnaei (CL) and its freshwater snail hosts is known to be context-dependent, ranging from mutualistic to parasitic. We monitored snail communities of seven streams in Germany during three seasons of a year and investigated infestation by CL. Some snail species never were infested. In snail species that were infested, size, substratum type, oxygen concentration and species identity were the most important variables explaining the variance in CL infestation. Independent of individual snail size, Bithynia tentaculata, Ancylus fluviatilis and Acroloxus lacustris showed the highest CL abundances. Across species, CL abundances were highest in large individuals on silty substratum at well-oxygenated sites. Reproductive success of snail populations was estimated from proportion of juveniles in populations. This measure of reproductive success of snail populations was inversely related with CL infestation level. These results suggest that CL infestation affects aquatic snails at the population and community level in the field. Differential infestation levels and different impacts of CL infestation between species lead to an asymmetric distribution of positive and negative effects among all snail species present in a habitat. Thus, CL may be an overlooked agent in structuring snail communities.

33. Metacommunity structuring in Himalayan streams over large elevational gradients: the role of dispersal routes and niche characteristics
2017 – Journal of Biogeography
Jonathan D. Tonkin, Ram Devi {Tachamo Shah}, Deep Narayan Shah, Felicitas Hoppeler, Sonja C. Jähnig, Steffen U. Pauls

Aim To examine metacommunity structuring in stream communities over large elevational gradients by disentangling physical and environmental structuring and the importance of different dispersal routes and niche characteristics.

32. Seasonality and predictability shape temporal species diversity
2017 – Ecology
Jonathan D. Tonkin, Michael T. Bogan, Núria Bonada, Blanca Rios-Touma, David A. Lytle

Temporal environmental fluctuations, such as seasonality, exert strong controls on biodiversity. While the effects of seasonality are well known, the predictability of fluctuations across years may influence seasonality in ways that are less well understood. The ability of a habitat to support unique, non-n- ested assemblages of species at different times of the year should depend on both seasonality (occurrence of events at specific periods of the year) and predictability (the reliability of event recurrence) of characteristic ecological conditions. Drawing on tools from wavelet analysis and information theory, we developed a framework for quantifying both seasonality and predictability of habitats, and applied this using global long--term rainfall data. Our analysis predicted that temporal beta diversity should be maximized in highly predictable and highly seasonal climates, and that low degrees of seasonality, predictability, or both would lower diversity in characteristic ways. Using stream invertebrate communities as a case study, we demonstrated that temporal species diversity, as exhibited by community turnover, was determined by a balance between temporal environmental variability (seasonality) and the reliability of this variability (predictability). Communities in highly seasonal mediterranean environments exhibited strong oscillations in community structure, with turnover from one unique community type to another across seasons, whereas communities in aseasonal New Zealand environments fluctuated randomly. Understanding the influence of seasonal and other temporal scales of environmental oscillations on diversity is not complete without a clear understanding of their predictability, and our framework provides tools for examining these trends at a variety of temporal scales, seasonal and beyond. Given the uncertainty of future climates, seasonality and predictability are critical considerations for both basic science and management of ecosystems (e.g., dam operations, bioassessment) spanning gradients of climatic variability.

2016

31. Environmental and spatial characterisation of an unknown fauna using DNA sequencing - an example with Himalayan Hydropsychidae (Insecta: Trichoptera)
2016 – Freshwater Biology
Felicitas Hoppeler, Ram Devi {Tachamo Shah}, Deep Narayan Shah, Sonja C. Jähnig, Jonathan D. Tonkin, Subodh Sharma, Steffen U. Pauls

Ecological studies of freshwater biota in understudied regions are often obstructed by poor taxonomic knowledge. We posit that molecular tools can help alleviate this issue and present an example where we combined molecular tools, environmental data and ecological statistics to investigate the distribution and community ecology of an unknown fauna of hydropsychid caddisflies along altitudinal gradients in four Himalayan river systems of Central and Eastern Nepal. A total of 484 larval specimens from 34 tributaries were examined. Phylogenetic analysis of the mitochondrial cytochrome c oxidase I (COI) and the nuclear ribosomal RNA 28S were used to delineate molecular operational taxonomic units (MOTUs) applying three analytical methods: general mixed Yule-coalescent (GMYC) model, Automatic Barcode Gap Discovery (ABGD) and Bayesian Phylogenetics and Phylogeography (BPP). Spatial distributional patterns and potential differences in ecological niches among MOTUs were statistically tested using regression and correlation approaches. Further, we examined the data for signs of non-random structure in MOTU communities. MOTU diversity within the family of Hydropsychidae was generally high but varied across evaluated gene fragments and slightly among delineation methods. Yet, the subsequent evaluation of environmental and spatial drivers and resulting distributional patterns were highly consistent among the different MOTU estimates. Within each river system, we found community composition varied greatly along the altitudinal gradients, with many MOTUs associated with specific altitudinal ranges. Prevalent MOTU turnover at the river system scale indicated high {\(\beta\)}-diversity in the hydropsychid community leading to high degrees of regional endemism. In the Langtang river system, we found fewer MOTU co-occurrences than expected by chance. These results highlight the utility of DNA-based approaches using variable genetic markers (mitochondrial or ribosomal nuclear) for primary biodiversity assessment of poorly studied groups or regions. Our study further shows that DNA-based biodiversity measures are suitable for downstream applications, such as exploring fundamental questions in stream ecology.

30. Time is no healer: increasing restoration age does not lead to improved benthic invertebrate communities in restored river reaches
2016 – Science of The Total Environment
Moritz Leps, Andrea Sundermann, Jonathan D. Tonkin, Armin W. Lorenz, Peter Haase

Evidence for successful restoration of riverine communities is scarce, particularly for benthic invertebrates. Among the multitude of reasons discussed so far for the lack of observed effects is too short of a time span between implementation and monitoring. Yet, studies that explicitly focus on the importance of restoration age are rare.

29. Scale-dependent effects of river habitat quality on benthic invertebrate communities — Implications for stream restoration practice
2016 – Science of The Total Environment
Stefan Stoll, Philippa Breyer, Jonathan D. Tonkin, Denise Früh, Peter Haase

Although most stream restoration projects succeed in improving hydromorphological habitat quality, the ecological quality of the stream communities often remains unaffected. We hypothesize that this is because stream communities are largely determined by environmental properties at a larger-than-local spatial scale. Using benthic invertebrate community data as well as hydromorphological habitat quality data from 1087 stream sites, we investigated the role of local- (i.e. 100 m reach) and regional-scale (i.e. 5 km ring centered on each reach) stream hydromorphological habitat quality (LQ and RQ, respectively) on benthic invertebrate communities. The analyses showed that RQ had a greater individual effect on communities than LQ, but the effects of RQ and LQ interacted. Where RQ was either good or poor, communities were exclusively determined by RQ. Only in areas of intermediate RQ, LQ determined communities. Metacommunity analysis helped to explain these findings. Species pools in poor RQ areas were most depauperated, resulting in insufficient propagule pressure for species establishment even at high LQ (e.g. restored) sites. Conversely, higher alpha diversity and an indication of lower beta dispersion signals at mass effects occurring in high RQ areas. That is, abundant neighboring populations may help to maintain populations even at sites with low LQ. The strongest segregation in species co-occurrence was detected at intermediate RQ levels, suggesting that communities are structured to the highest degree by a habitat/environmental gradient. From these results, we conclude that when restoring riverine habitats at the reach scale, restoration projects situated in intermediate RQ settings will likely be the most successful in enhancing the naturalness of local communities. With a careful choice of sites for reach-scale restoration in settings of intermediate RQ and a strategy that aims to expand areas of high RQ, the success of reach-scale restoration in promoting the ecological quality of communities can be greatly improved.

28. Anthropogenic land-use stress alters community concordance at the river-riparian interface
2016 – Ecological Indicators
Jonathan D. Tonkin, Stefan Stoll, Sonja C. Jähnig, Peter Haase

Organisms often respond in similar ways to environmental or spatial gradients, particularly at large spatial scales. Yet, while understanding these relationships is important for both basic and applied purposes, such as identifying surrogate taxa for conservation and monitoring purposes, patterns at finer scales and across ecotones are less certain. Our central aim was to explore patterns in community concordance at the river-riparian interface and examine whether concordance was decoupled by increasing anthropogenic stress (a gradient of local land-use intensity). We explored this at 15 sites over three years within the LTER site, Rhine-Main-Observatory, a low mountain river system in central Germany, assessing concordance between four organism groups: riparian spiders and carabid beetles, benthic macroinvertebrates, and combined aquatic macrophytes and riparian plants. This represented three different linkages: (1) predator–prey, (2) direct competition, and (3) habitat associations. While there were no correlations in richness patterns, multivariate community structure was highly concordant between all groups. Anthropogenic stress strongly reduced links between riparian spiders and carabid beetles, likely resulting from their shared resource requirements. However, increasing concordance generally occurred between plants and other groups, although inconsistently between the three groups. We posit that patterns may be resulting from two processes: (1) linkages between directly competing species decouple with increasing anthropogenic stress, and (2) stronger coupling may occur between habitat providers and dependent species when overall habitat complexity is reduced. Our results highlight the complex manner in which anthropogenic stress can influence ecosystem structure, particularly at small scales. Based on these complexities, we recommend considering the full suite of community data to adequately explore biodiversity patterns or when searching for surrogate taxa.

27. Context dependency in biodiversity patterns of central German stream metacommunities
2016 – Freshwater Biology
Jonathan D. Tonkin, Jani Heino, Andrea Sundermann, Peter Haase, Sonja C. Jähnig

Context dependency is an emerging topic that is challenging our understanding of the factors shaping biodiversity in metacommunities. River networks and other dendritic systems provide unique systems for examining variation in the processes shaping biodiversity between different metacommunities. We examined biodiversity patterns in five benthic invertebrate data sets, from two catchments in central Germany, with the aim of exploring context dependency in these systems. We used variance partitioning to disentangle the variation explained in three biodiversity metrics: taxonomic richness, Simpson’s diversity and local contribution to beta diversity (LCBD; a measure of the uniqueness of a site). As explanatory variables, we used proxies of network position (i.e. catchment size and altitude) and habitat conditions. Contrary to our expectation, we found no evidence of a decline in LCBD downstream in our study. Local habitat conditions and catchment land use played a much stronger role than catchment size and altitude in explaining variation in the three biodiversity metrics. Observed patterns were highly variable between different data sets in our study. These findings suggest that factors shaping biodiversity patterns in these systems are highly context dependent and less related to their position along the river network than local habitat conditions. Given the clear context dependency between data sets, we urge researchers to focus on disentangling the factors driving the high levels of variability between individual systems through the study of a number of replicate, rather than single, metacommunities.

26. Contrasting metacommunity structure and beta diversity in an aquatic-floodplain system
2016 – Oikos
Jonathan D. Tonkin, Stefan Stoll, Sonja C. Jähnig, Peter Haase

Habitat connectivity and dispersal interact to structure metacommunities, but few studies have examined these patterns jointly for organisms across the aquatic–terrestrial ecotone. We assessed metacommunity structure and beta diversity patterns of instream benthic invertebrates, riparian carabid beetles (Order: Coleoptera; Family: Carabidae) and riparian spiders (Order: Araneae) at fifteen sites in a river-floodplain system. Sampling took place over a three-year period (2010–2012) in the Rhine-Main-Observatory LTER site on the Kinzig River, central Germany. This allowed disentangling the combined influence, and temporal variability, of habitat connectivity (i.e. between aquatic and terrestrial) and dispersal ability (i.e. between spiders and beetles, and aerial and aquatic dispersing invertebrates) on the dominant paradigms structuring these metacommunities. We found mostly consistent differences in the manner that metacommunities were structured between groups, with lower levels of variability explained for beetles compared to the other groups. Beetles were consistently structured more by turnover than nestedness components, with greater beta diversity than expected by chance and a minor spatial compared to environmental signal emerging with variance partitioning. Conversely, spiders and benthic invertebrates had lower beta diversity and greater nestedness than null expectation, and a clearer spatial signal controlling metacommunity structure. Our results suggest varying levels of mass effects and species sorting shape river-floodplain metacommunities, depending on habitat connectivity and dispersal ability. That is, greater connectivity and lower fragmentation along the river compared to the terrestrial zone promoted mass effects, and differences in overall dispersal ability and mode (i.e. active and passive) for instream and riparian communities shifted paradigms between mass effects and species sorting.

25. Elements of metacommunity structure of river and riparian assemblages: Communities, taxonomic groups and deconstructed trait groups
2016 – Ecological Complexity
Jonathan D. Tonkin, Stefan Stoll, Sonja C. Jähnig, Peter Haase

The elements of metacommunity structure (EMS) framework gives rise to important ecological insights through the distinction of metacommunities into several different idealised structures. We examined the EMS in assemblages occupying a low-mountain river system in central Germany, sampled over three consecutive years. We compared the idealised distributions of assemblages in both the riparian floodplain zone (carabid beetles and spiders) and the benthic instream environment (benthic invertebrates). We further deconstructed instream organisms into taxonomic and trait groups to examine whether greater signal emerges in more similar species groups. We found little evidence of strong competition, even for trait-modality groups, and nestedness was almost non-existent. In addition to random distributions, Gleasonian distributions (indicating clear, but individualistic turnover between sites) were the most commonly identified structure. Clear differences were apparent between different trait groups, particularly between within-trait modalities. These were most evident for different dispersal modes and life cycle durations, with strong dispersers showing possible signs of mass effects. While random distributions may have partly reflected small sample sizes, clearly coherent patterns were evident for many groups, indicating a sufficient gradient in environmental conditions. The prevalence of random distributions suggests many species are responding to a variety of environmental filters in these river-floodplain metacommunities in an anthropogenically-dominated landscape, whereas Gleasonian distributions indicate species are responding idiosyncratically to a primary environmental gradient. Our findings further emphasise the prevalence of context dependency (spatio-temporal variability) in metacommunity studies, thus we stress the need to further disentangle the causes of such variation.

24. Exploring stream communities in a tropical biodiversity hotspot: biodiversity, regional occupancy, niche characteristics and environmental correlates
2016 – Biodiversity and Conservation
Jonathan D. Tonkin, Francis O. Arimoro, Peter Haase

Exploring and describing biodiversity and the mechanisms structuring it is fundamental to advancing ecology. This is particularly pertinent in understudied biogeographical regions, such as the Afrotropics, that are characterised by strong seasonal climatic shifts. We investigated the characteristics of stream biodiversity in the Niger Delta region of Nigeria, a tropical biodiversity hotspot, by examining patterns in 20 stream invertebrate communities across both the wet and dry seasons. For this, we took a multi-faceted approach accounting for the three levels of biodiversity ({\(\alpha\)}, {\(\beta\)} and {\(\gamma\)}), including partitioning the nestedness and turnover components of {\(\beta\)} diversity, regional occupancy-abundance patterns, niche characteristics, and the environmental drivers of community structure. {\(\alpha\)} diversity was low in these streams, with strong turnover between sites leading to high {\(\beta\)} diversity contributing to regional biodiversity, but there was little variation in communities between seasons. The proportion of sites occupied by taxa declined with increasing niche position, and decreasing niche breadth. Occupancy was predicted well by a combination of these two factors (niche position and breadth), but not mean local abundance, as the abundance-occupancy link was an upper-limit unimodal relationship. On average, community structure was linked more strongly to environmental variables in the wet season. Our findings demonstrate the clear role of spatial, but not temporal, turnover in assemblages, which likely reflects the environmental heterogeneity of this region. This is further supported by the fact that regional occupancy was mostly related to niche characteristics, particularly niche position. We emphasise the importance of continued basic and applied ecological work in this important biogeographic region to enable better protection of its biodiversity.

2015

23. A preliminary survey of altitudinal variation in two ground weta species, Hemiandrus maculifrons (Walker) and Hemiandrus pallitarsis (Walker) (Orthoptera: Anostostomatidae)
2015 – New Zealand Entomologist
Esta M. Chappell, David S. Webb, Adam J. Brown, Jonathan D. Tonkin

Species’ ranges along altitudinal clines are probably influenced by their ability to adapt to a range of abiotic factors. Physical adaptations in response to lower temperatures at higher altitudes often include changes in body size. We investigated the distribution and potential change in body size with altitude of two species of ground w{=e}t{=a}, Hemiandrus maculifrons and Hemiandrus pallitarsis in the Moehau Ecological Area on the Coromandel Peninsula, North Island, New Zealand. Over eight nights of searching, 17 adult H. maculifrons and 28 adult H. pallitarsis were found. Hemiandrus maculifrons was the smaller of the two species and was found at higher altitudes compared with H. pallitarsis (91–577 m and 27–207 m, respectively). No ground w{=e}t{=a} were caught in baited and unbaited live-catch pitfall traps (40 set at 211–242 m above sea level; 40 at 620–626 m above sea level). Despite what appeared to be a tendency for the size of male H. maculifrons to increase with altitude, we found no evidence of intraspecific variation in body size with altitude although sample sizes were small. Nevertheless, these two species of ground w{=e}t{=a} appear well suited to further investigations into aspects associated with factors that influence body size, distributional range shifts and climate change.

22. Community-environment relationships of riverine invertebrate communities in central Chinese streams
2015 – Environmental Earth Sciences
Sonja C. Jähnig, Deep Narayan Shah, Ram Devi {Tachamo Shah}, Fengqing Li, Qinghua Cai, Andrea Sundermann, Jonathan D. Tonkin, Sonja Stendera

Chinese rivers are both highly biodiverse and highly under pressure, hence an urgent need exists to understand ecological drivers and disentangle different scales of stressors to support water management. Our aims were to (1) determine the most influential variables for benthic invertebrate occurrence, (2) compare results related to communities as opposed to metrics and (3) examine the role of spatial scales with relevance to management. Benthic invertebrate sampling was performed at 37 sites in selected tributaries of the middle reaches of the Yangtze, covering an environmental gradient with a focus on organic pollution (stratified sampling design). Ten metrics commonly used in biomonitoring were derived and analysed in parallel to assemblage data. Environmental variables covered 74 parameters from three different spatial scales, namely local, reach and catchment scale. We ran a CCA with each of the three subsets to find out the significant determining/explanatory variables, followed by pCCA and pRDA (for metric data) with these variables with forward selection to determine single variables important for each subset; we further used variation portioning for benthic invertebrate data. A high percentage of overall variability (70 %) of the assemblage structure was explained, with catchment- and local-scale variables being almost equally important. Small-scale variables tended to be more important than large-scale variables for the metric-based approach but not for the assemblage approach. Our results emphasise the need for spatially explicit regional studies in freshwater systems and suggest testing multi-metric assessment approaches to tackle water management and environmental health questions in China.

21. Disentangling environmental drivers of benthic invertebrate assemblages: The role of spatial scale and riverscape heterogeneity in a multiple stressor environment
2015 – Science of The Total Environment
Moritz Leps, Jonathan D. Tonkin, Veronica Dahm, Peter Haase, Andrea Sundermann

It is broadly acknowledged that freshwater ecosystems are affected by multiple stressors, but the relative importance of individual stressors in impairing riverine communities remains unclear. We investigated the impacts of multiple stressors, incorporating in-stream water quality, riparian and catchment land use and stream morphology, on riverine benthic invertebrate communities, while considering the spatial scales of factors and the heterogeneity of riverscapes. We performed a stepwise regression procedure linking 21 abiotic and 20 community metrics using Generalized Linear Models on data from 1018 river sites spread across Germany. High impact stressors (e.g., nutrients and water temperature) were identified for various community metrics. Both the combination of relevant stressors and their explanatory value differed significantly across streams of different sizes and ecoregions. In large rivers, the riparian land use was less important in determining community structure compared to lower order streams. Thus, possible mitigating effects of revegetated riparian buffer strips are likely to be overwhelmed by the influence of catchment-wide land use. Our results indicated substantial variability in stressors for the range of metrics studied, providing insight into potential target parameters for effective ecosystem management. To achieve long lasting successes in managing, protecting and restoring running waters, it is of vital importance to recognize the heterogeneity of riverscapes and to consider large-scale influences.

20. Latitudinal patterns and large-scale environmental determinants of stream insect richness across Europe
2015 – Limnologica
Deep Narayan Shah, Jonathan D. Tonkin, Peter Haase, Sonja C. Jähnig

Latitudinal patterns have been widely studied in many organism groups, such as terrestrial vertebrates or plants, along with a suite of other large-scale biodiversity-environment gradients. Much less is known about these patterns for freshwater organisms, particularly stream insects. We evaluated European stream insect richness along a latitudinal gradient (39{\(^\circ\)}–68{\(^\circ\)} N) and estimated how much of the variation in taxon richness patterns could be explained by natural drivers: current climate, geographic location and topography. We assessed richness patterns using two datasets. First, based on 1318 sampling sites, we calculated taxon richness of juveniles stages of aquatic insects in 1{\(^\circ\)} {} 1{\(^\circ\)} grid cells and converted these into latitudinal bands. Second, we calculated taxonomic richness using species lists from www.freshwaterecology.info for the ecoregions of European freshwaters. We evaluated Ephemeroptera, Plecoptera and Trichoptera (EPT) richness patterns for both latitudinal band and ecoregion data using linear regression, comparing list-based with grid-based data compiled for each region. We then estimated both pure and combined effects of each group of environmental variables using variance partitioning. Both individually and combined, EPT taxon richness declined with increasing latitude. Taxon richness was high between 42{\(^\circ\)} and 46{\(^\circ\)} N, geographically representing the Alps, and a threshold was detected at 48{\(^\circ\)} N for all three groups and combined EPT using the grid data. Current climate, geographic location, and topographic predictors explained over 50% of the variation in taxonomic richness (E – 52%; P – 59%; T – 57%; overall EPT – 57%). A greater pure effect was observed for current climate than geographic locations and topographic predictors. We discuss other potential factors such as past glaciation, dispersal and anthropogenic stressors such as land use, river engineering, or pollution that might have shaped the present distribution of species.

19. Climatic and catchment-scale predictors of Chinese stream insect richness differ between taxonomic groups
2015 – PLOS ONE
Jonathan D. Tonkin, Deep Narayan Shah, Mathias Kuemmerlen, Fengqing Li, Qinghua Cai, Peter Haase, Sonja C. Jähnig

Little work has been done on large-scale patterns of stream insect richness in China. We explored the influence of climatic and catchment-scale factors on stream insect (Ephemeroptera, Plecoptera, Trichoptera; EPT) richness across mid-latitude China. We assessed the predictive ability of climatic, catchment land cover and physical structure variables on genus richness of EPT, both individually and combined, in 80 mid-latitude Chinese streams, spanning a 3899-m altitudinal gradient. We performed analyses using boosted regression trees and explored the nature of their influence on richness patterns. The relative importance of climate, land cover, and physical factors on stream insect richness varied considerably between the three orders, and while important for Ephemeroptera and Plecoptera, latitude did not improve model fit for any of the groups. EPT richness was linked with areas comprising high forest cover, elevation and slope, large catchments and low temperatures. Ephemeroptera favoured areas with high forest cover, medium-to-large catchment sizes, high temperature seasonality, and low potential evapotranspiration. Plecoptera richness was linked with low temperature seasonality and annual mean, and high slope, elevation and warm-season rainfall. Finally, Trichoptera favoured high elevation areas, with high forest cover, and low mean annual temperature, seasonality and aridity. Our findings highlight the variable role that catchment land cover, physical properties and climatic influences have on stream insect richness. This is one of the first studies of its kind in Chinese streams, thus we set the scene for more in-depth assessments of stream insect richness across broader spatial scales in China, but stress the importance of improving data availability and consistency through time.

18. Environmental controls on river assemblages at the regional scale: An application of the elements of metacommunity structure framework
2015 – PLOS ONE
Jonathan D. Tonkin, Andrea Sundermann, Sonja C. Jähnig, Peter Haase

Understanding factors that structure regional biodiversity is important for linking ecological and biogeographic processes. Our objective was to explore regional patterns in riverine benthic invertebrate assemblages in relation to their broad positioning along the river network and examine differences in composition, biodiversity (alpha and beta diversity), and environmental drivers. We up-scaled methods used to examine patterns in metacommunity structure (Elements of Metacommunity Structure framework) to examine faunal distribution patterns at the regional extent for 168 low-mountain stream invertebrate assemblages in central Germany. We then identified the most influential environmental factors using boosted regression trees. Faunal composition patterns were compartmentalised (Clementsian or quasi-Clementsian), with little difference from headwaters to large rivers, potentially reflecting the regional scale of the study, by crossing major catchment boundaries and incorporating different species pools. While idealised structures did not vary, environmental drivers of composition varied considerably between river sections and with alpha diversity. Prediction was substantially weaker, and the importance of space was greater, in large rivers compared to other sections suggesting a weakening in species sorting downstream. Further, there was a stronger transition in composition than for alpha diversity downstream. The stronger links with regional faunal composition than with richness further emphasises the importance of considering the alternative ways in which anthropogenic stressors are operating to affect biodiversity patterns. Our approach allowed bridging the gap between local (or metacommunity) and regional scales, providing key insights into drivers of regional biodiversity patterns.

17. Small-scale patch complexity, benthic invertebrate colonisation and leaf breakdown in three headwater streams in Bay of Plenty, New Zealand
2015 – New Zealand Journal of Marine and Freshwater Research
Jonathan D. Tonkin, Adam Brown, Esta M. Chappell

We assessed the effects of patch complexity on benthic macroinvertebrate colonisation and leaf breakdown in three headwater streams in the Kaimai Range, New Zealand. We used three patch types: complex, disturbed, and unaltered control patches, and measured colonisation of macroinvertebrates and leaf breakdown rates within each patch. We hypothesised colonisation and breakdown would be highest in the complex patches and lowest in disturbed patches. With the exception of percentage of total shredders, no differences were found in macroinvertebrate diversity or community structure and no treatment effect was evident for leaf breakdown rates. While this may suggest no influence of patch complexity on leaf breakdown, we cannot discount unmeasured site-specific influences, such as a high flow event, which occurred during the treatment period, as clear differences were evident between the three streams. Higher spatiotemporal replication and more appropriate seasonal sampling would be required to further explore this relationship.

2014

16. Notes on sexual size dimorphism, sex ratio and movements of adult ground weta {} (Walker) (Orthoptera: Anostostomatidae)
2014 – New Zealand Entomologist
Esta M. Chappell, David S. Webb, Jonathan D. Tonkin

The ground weta (Hemiandrus maculifrons) is an apparently abundant species with a New Zealand-wide distribution. Despite this, there is a paucity of ecological and biological information concerning this species. We aimed to gain new information about movement patterns, capture rates and body size differences by tagging individuals and conducting nightly surveys of a single H. maculifrons population in the Otanewainuku Forest, Bay of Plenty, New Zealand. Over a 26-night period between March and April 2012, we tagged 53 females and 78 males with queen bee tags and small reflector strips and recorded the location of animals that were subsequently re-sighted. Adult females were significantly larger than males, but capture and re-sight rates suggested males were the more abundant sex during the study period. Female weta moved further over consecutive nights than males (average distance moved, 1.57 m vs. 1.01 m, respectively); however, the tagging method, time of year and study area may have resulted in underestimates. These results indicate areas for further research into aspects of sexual selection, such as potentially biased sex ratios, sexual size dimorphism and mate competition, within H. maculifrons.

15. Learning the ropes: mussel spat ropes improve fish and shrimp passage through culverts
2014 – Journal of Applied Ecology
Bruno O. David, Jonathan D. Tonkin, Kristopher W. T. Taipeti, Hayden T. Hokianga

Culvert pipes are regularly used around the world for conveying stream flows underground, through embankments or under road crossings. Installation of these features can have significant negative effects on the passage of freshwater biota and potentially exclude many species from large areas of river networks. We investigated the installation of mussel spat ropes as a potentially rapid and cost-effective tool for improving passage of freshwater biota through culvert pipes where internal barrel conditions impede passage. We assessed passage success for two fish species, juvenile rainbow trout Oncorhynchus mykiss (Walbaum 1972) and adult inanga Galaxias maculatus (Jenyns 1842), and one migratory shrimp, Paratya curvirostris (Heller 1862), through culverts of differing length (3 and 6 m), slope (1{\(\cdot\)}5 and 3{\(^\circ\)}) and flow (0{\(\cdot\)}24 and 0{\(\cdot\)}75 L s-1). We hypothesized that ropes would enhance the passage success of these three species, but success rates would differ between species and trial combinations. Ropes resulted in a reduced water velocity within culvert barrels and significantly improved passage success for all three species. Shrimp benefited most by the presence of ropes, being unable to negotiate any of the pipe combinations in their absence, but exhibiting varying rates of success across all combinations with their presence. Both G. maculatus and O. mykiss were able to negotiate some of the non-roped pipe combinations, but as the level of difficulty increased, successful passage was only achieved with the ropes present. Synthesis and applications. We conclude that this relatively inexpensive and easy-to-install tool has the potential to substantially improve passage for a range of aquatic biota through various culvert scenarios. We consider that ropes would be particularly useful in situations where internal culvert access is difficult and where various culvert parameters (slope, flow, length) result in internal barrel hydraulics that would normally limit or exclude passage of aquatic biota.

14. The combined effects of flow regulation and an artificial flow release on a regulated river: flow regulation on the Tongariro River
2014 – River Research and Applications
Jonathan D. Tonkin, Russell G. Death

Damming and regulating the flow of rivers is a widespread issue and can have a significant impact on resident biota. The Tongariro River, central North Island, New Zealand, has a flow regime that is regulated by two hydroelectric dams along its length, and it has been suggested that flushing flows' would assist benthic communities by removingnuisance’ periphyton growth forms that typically occur in autumn. We assessed whether (i) damming has altered periphyton and macroinvertebrate communities downstream of the Rangipo Dam and (ii) whether the release of a flow pulse equivalent to 50 times the baseflow is sufficient to (a) move the substrate in the section of river downstream of this dam and (b) impact benthic periphyton and macroinvertebrate communities. Downstream macroinvertebrate communities were impacted by the presence of the dam, but periphyton was not. No movement of substrate occurred downstream of the dam as a result of the flow release, which was likely because of naturally high embeddedness and armouring of substrate. Periphyton biomass and macroinvertebrate density were not affected by the release indicating that larger releases would be required to have any effect on benthic communities downstream of this dam. This study highlights the importance of considering natural bed structure and sediment dynamics when using flow releases downstream of dams to control periphyton. Copyright {} 2013 John Wiley & Sons, Ltd.

13. Dispersal distance and the pool of taxa, but not barriers, determine the colonisation of restored river reaches by benthic invertebrates
2014 – Freshwater Biology
Jonathan D. Tonkin, Stefan Stoll, Andrea Sundermann, Peter Haase

Restoration is an increasingly central theme in river ecology. Recent studies have highlighted the importance of the species pool in the surrounding river network for determining colonisation of restored river reaches by both invertebrates and fish. Using a comprehensive data set of 21 river restoration sites and 292 sites in the immediate surroundings, we tested the influence of distance to nearest colonist source on invertebrate colonisation based on a comparison of river network distances and Euclidean distances, expecting river network distances would better align with colonisation rates. We then assessed the importance of dispersal distance in relation to several other parameters, such as the number and intensity of barriers along the river network, surrounding taxon pool occupancy rate, physical characteristics of the restored sites and restoration techniques used in determining colonisation of commonly occurring benthic invertebrates. We hypothesised that (i) distance would be critical, with colonisation of restored sites declining with increasing distance; (ii) barriers between these sites would be a minor, but taxon-specific, influence on the colonisation; and (iii) the higher the regional pool occupancy rate of a certain taxon, the higher its probability of presence at a restored site. Overall, taxon pool occupancy rate was the most important driver of colonisation likelihood, followed by distance to nearest source, with the first kilometre particularly important. The effect of barriers was minor but significant, and taxon identity had no effect on the predictive ability of the model. Factors associated with the restoration projects such as techniques used and physical characteristics had minor influences, being completely outweighed by taxon pool and dispersal-related factors. To gauge the likelihood of successful outcomes of habitat restoration projects, we suggest it is important to assess regional taxon pools and ensure distances between healthy populations are minimised. These results clearly emphasise the importance of spatial planning for restoration projects.

12. Drivers of macroinvertebrate community structure in unmodified streams
2014 – PeerJ
Jonathan D. Tonkin

Often simple metrics are used to summarise complex patterns in stream benthic ecology, thus it is important to understand how well these metrics can explain the finer-scale underlying environmental variation often hidden by coarser-scale influences. I sampled 47 relatively pristine streams in the central North Island of New Zealand in 2007 and (1) evaluated the local-scale drivers of macroinvertebrate community structure as well as both diversity and biomonitoring metrics in this unmodified landscape, and (2) assessed whether these drivers were similar for commonly used univariate metrics and multivariate structure. The drivers of community metrics and multivariate structure were largely similar, with % canopy cover and resource supply metrics the most commonly identified environmental drivers in these pristine streams. For an area with little to no anthropogenic influence, substantial variation was explained in the macroinvertebrate community (up to 70% on the first two components of a partial least squares regression), with both uni- and multivariate approaches. This research highlights two important points: (1) the importance of considering natural underlying environmental variation when assessing the response to coarse environmental gradients, and (2) the importance of considering canopy cover presence when assessing the impact of stressors on stream macroinvertebrate communities.

11. Periphyton control on stream invertebrate diversity: is periphyton architecture more important than biomass?
2014 – Marine and Freshwater Research
Jonathan D. Tonkin, Russell G. Death, José Barquín

There is little consensus on the form of the periphyton biomass–macroinvertebrate diversity relationship in streams. One factor that these relationships do not account for is the growth form of primary producers. We (1) examined the periphyton biomass–macroinvertebrate diversity relationship in 24 streams of Cantabria, Spain, in July 2007, and (2) determined whether this relationship was underpinned, and better explained, by specific responses to the growth form of the periphyton community. We hypothesised that macroinvertebrate diversity would be a log-linear function of periphyton biomass and would respond differently to two coarse divisions of the periphytic community; i.e. positively to %cover of non-filamentous algae and negatively to %cover of streaming filamentous algae. There was no relationship between benthic periphyton biomass and macroinvertebrate diversity in these streams but, as predicted, this relationship was underpinned by responses to the growth form of periphyton community. Generally, macroinvertebrate diversity responded positively to %cover of non-filaments and negatively to %cover of streaming filaments, although results were variable. These findings suggest that periphyton biomass–macroinvertebrate diversity relationships in streams can be underpinned by interactions with specific growth forms of periphyton. We suggest that further research is required to develop robust thresholds of %cover of filamentous algae cover that would benefit managers wishing to minimise negative effects of eutrophication on stream communities.

10. The rise of riverine flow-ecology and environmental flow research
2014 – Environmental Processes
Jonathan D. Tonkin, Sonja C. Jähnig, Peter Haase

Rivers worldwide are under increasing threat from hydrologic alteration. Managing for environmental flows (E-flows) is one way of dealing with this, but research remains heavily focused on development of methods for setting flows. We examined trends in riverine flow-ecology research (the link between the flow regime and biota of a river) from 1995 to 2012 internationally by assessing publication rate of all countries combined and identifying trends in research specifically on E-flows. USA dominated the research output in flow-ecology research, but Australian researchers were the most active on E-flows. We show that E-flow research has exponentially expanded since the mid 1990s, both in number and as a percentage of general river research. Eflow research productivity also increased weakly with the number of dams and per-capita gross domestic product (GDP) of countries, highlighting that this research is performed mostly in developed countries. We expect this trend will continue and suggest that E-flow research needs to be incorporated into policy in low-GDP countries to ensure healthy viable river ecosystems.

2013

9. Macroinvertebrate drift-benthos trends in a regulated river
2013 – Fundamental and Applied Limnology
Jonathan D. Tonkin, Russell G. Death

Downstream drift plays a fundamental role in the spatial distribution and community structure of lotic macroinvertebrates. We sampled both benthic and drifting macroinvertebrates at 15 sites, in three sections of river with varying flow alteration along the Tongariro River, New Zealand. Our objectives were to examine whether (i) benthic and drift density were linearly related throughout the river, (ii) the presence of dams affected the propensity of macroinvertebrates to drift, and (iii) drift propensity was related to benthic periphyton biomass or natural longitudinal patterns down the river. More taxa were collected from the drift than the benthos, although drift and benthic samples were generally taxonomically similar, despite some structural differences. Nonetheless, differences were evident between the major groups when assessing density and relative abundance links between the benthos and drift. The presence of dams did not affect the propensity of macroinvertebrates to drift on the whole, nor was propensity affected by periphyton biomass or distance from source. These results suggest that although altered periphyton biomass in downstream sections in the Tongariro River is altering the composition of benthic and drifting macroinvertebrates, drift propensity is unaffected. However, some deviations from linear relationships between benthic and drift density are evident suggesting these links may be taxon specific.

8. Do productivity and disturbance interact to modulate macroinvertebrate diversity in streams?
2013 – Hydrobiologia
Jonathan D. Tonkin, Russell G. Death, Kevin J. Collier

Although disturbance and productivity are clearly strong influences on lotic diversity, rarely have their interactive effects been studied in running water systems. We hypothesised that the presence or absence of canopy cover in streams would alter productivity–disturbance–diversity relationships due to differential effects on the food base, and tested this hypothesis in 47 mountain streams in the central North Island of New Zealand. Canopy cover had no influence on algal biomass in these streams, but a link between disturbance and productivity was found in open canopy streams where taxonomic richness of invertebrates increased log-linearly with increasing algal biomass and peaked at intermediate levels of disturbance. Community evenness declined with disturbance, but only at closed canopy sites where both invertebrate taxonomic richness and Simpson’s diversity index were higher. Although there was a peak in richness at intermediate rates of disturbance, our results do not directly match predictions of the dynamic equilibrium model which predicts that the level of disturbance maximising diversity interacts with habitat productivity. Rather, we suggest the combined effects of productivity and disturbance are additive rather than multiplicative such that productivity simply sets the upper limit to richness in streams.

7. Productivity-diversity relationships for stream invertebrates differ geographically
2013 – Aquatic Ecology
Jonathan D. Tonkin, Russell G. Death, José Barquín

More productive environments typically have more species, although the specific form of this relationship is unclear and can vary with spatial scale. This relationship has received little direct attention in lotic systems, and thus the nature of the relationship is unclear, as is any effect of spatial scale. We examined the link between stream primary productivity and macroinvertebrate diversity in Spain and New Zealand and hypothesized that macroinvertebrate diversity would increase log-linearly with increasing productivity in both regions. We sampled 24 streams in Cantabria, Spain, and 24 in the central North Island, New Zealand. Algal primary productivity was approximately three times higher in Spanish streams, but taxonomic richness of invertebrates did not differ between the regions. Richness and Shannon diversity only responded to productivity in the New Zealand streams, exhibiting the predicted log-linear increase. In the Spanish streams, only the total number of individuals increased with productivity. However, when plotted on the same axes, richness in the Spanish streams simply occurred on the linear portion of the graph to the right of the New Zealand streams. We speculate that productivity in the Spanish streams never became low enough to constrain diversity, but did in the New Zealand streams. Combining results from the two regions, there is no evidence of a decline in diversity with higher productivity.

6. Scale dependent effects of productivity and disturbance on diversity in streams
2013 – Fundamental and Applied Limnology
Jonathan D. Tonkin, Russell G. Death

The effects of productivity and disturbance on diversity vary widely with the spatial scale at which they are examined. Not only do productivity and disturbance have strong influences on diversity patterns at local and regional scales but they can affect the way in which communities assemble and in turn alter beta diversity or community dissimilarity. We assessed whether the form of both the productivity- and disturbance-diversity relationships differed between the spatial scale at which they were examined using experimental stream channels in three Hawke’s Bay, New Zealand streams. In place of true local and regional richness, we used the proxies within- and between-stream richness, as well as assessing between-stream community dissimilarity (similar to beta diversity). Our results indicate that productivity and disturbance both affect diversity but at individual scales and in different forms. At the within-stream scale, richness was a u shaped function of productivity whereas at the between-stream scale richness increased monotonically with increasing productivity. Community dissimilarity on the other hand, increased monotonically with increasing rate of disturbance. Rather than a greater role of deterministic assembly with increasing disturbance, our results indicate the opposite, but it appears that communities are simply converging on those found in the surrounding streambed with time since disturbance. Specifically, communities were more similar within individual streams than within disturbance treatments and animals colonizing post-disturbance were simply a subset of taxa present at each site regardless of perceived colonizing ability, rather than a suite of specialist colonizing taxa. These results demonstrate that without a distinction between early and late colonizers, a greater rate of deterministic assembly at high disturbance will not occur.

2012

5. A new approach to assess bed stability relevant for invertebrate communities in upland streams: a new approach to assess bed stability
2012 – River Research and Applications
Arved C. Schwendel, Russell G. Death, Ian C. Fuller, Jonathan D. Tonkin

Composition and structure of lotic ecosystems can be affected by substrate instability. Consequently stream ecologists have used various methods to determine bed stability characteristics. However, the link between community composition and these measurements varies because benthic biota often responds to combinations of bed stability characteristics. This paper presents a protocol to determine reach-scale stream bed stability in mountain streams which is relevant for invertebrate communities (Stream Bed Stability for Invertebrates, SBSI). The approach is calibrated on community composition response to bed stability but does not measure any single bed stability characteristic per se. It consists of 13 parameters that are assessed once at each reach with minimal instrumentation and low interference with the substrate. These 13 parameters cover aspects of sediment supply from banks, transport capacity and substrate erodibility as well as effects of particle transport on channel bottom structures, substrate assemblage and single grains. Application of the SBSI protocol improved the relationship between bed stability and community diversity compared to when conventional bed stability measures were employed. The SBSI protocol provides a cost-effective and time-effective assessment method for bed stability and its application can facilitate research on invertebrate community response to physical disturbance. Copyright {} 2011 John Wiley & Sons, Ltd.

4. Consistent effects of productivity and disturbance on diversity between landscapes
2012 – Ecosphere
Jonathan D. Tonkin, Russell G. Death

Productivity and disturbance have a strong role in determining diversity patterns in nature yet whether they operate individually or interact to determine diversity is unclear. Moreover, what effect land-use change has on this relationship has not been assessed. We tested whether land use influenced the relationship between productivity, disturbance and diversity, and assessed the fit of three productivitydisturbance-diversity models, using data from multiple samplings of 16 streams in two contrasting regions of the North Island of New Zealand. As the Dynamic Equilibrium Model (DEM) has received inconsistent support in all ecosystems and little favorable applications in lotic systems, we applied this along with two previously developed for stream communities. Although the community structure differed between the two regions, the response of taxonomic richness to productivity and disturbance was consistent. That is, richness was log-linearly related to productivity and declined monotonically with disturbance. However, there was no evidence of an interactive effect of productivity and disturbance. When accounting for density (rarefaction) the results were inconsistent, exhibiting no relationship with productivity but declining with disturbance. Our results suggest both the Death and Tonkin productivity-disturbance-diversity models are the most applicable in these communities where disturbance simply removes taxa and productivity controls the upper limit to richness.

3. Mussel spat ropes assist redfin bully Gobiomorphus huttoni passage through experimental culverts with velocity barriers
2012 – Water
Jonathan D. Tonkin, Liam A.H. Wright, Bruno O. David

The application of mussel spat rope for enabling the passage of redfin bully Gobiomorphus huttoni through culverts, which create velocity barriers, was trialled in the laboratory. No fish were able to access the un-roped control pipes whereas 52% successfully negotiated the pipes in the rope treatments. The success of fish ascending treatment pipes suggests mussel spat rope may be effective for enabling the passage of this and other similar fish species through otherwise impassable culverts with velocity barriers.

2009

2. Ecological values of Hamilton urban streams (North Island, New Zealand): constraints and opportunities for restoration
2009 – New Zealand Journal of Ecology
Kevin J. Collier, Amy Macdonald, Brian J. Smith, Jonathan D. Tonkin

Urban streams globally are characterised by degraded habitat conditions and low aquatic biodiversity, but are increasingly becoming the focus of restoration activities. We investigated habitat quality, ecological function, and fish and macroinvertebrate community composition of gully streams in Hamilton City, New Zealand, and compared these with a selection of periurban sites surrounded by rural land. A similar complement of fish species was found at urban and periurban sites, including two threatened species, with only one introduced fish widespread (Gambusia affinis). Stream macroinvertebrate community metrics indicated low ecological condition at most urban and periurban sites, but highlighted the presence of one high value urban site with a fauna dominated by sensitive taxa. Light-trapping around seepages in city gullies revealed the presence of several caddisfly species normally associated with native forest, suggesting that seepage habitats can provide important refugia for some aquatic insects in urban environments. Qualitative measures of stream habitat were not significantly different between urban and periurban sites, but urban streams had significantly lower hydraulic function and higher biogeochemical function than periurban streams. These functional differences are thought to reflect, respectively, (1) the combined effects of channel modification and stormwater hydrology, and (2) the influence of riparian vegetation providing shade and enhancing habitat in streams. Significant relationships between some macroinvertebrate community metrics and riparian vegetation buffering and bank protection suggest that riparian enhancement may have beneficial ecological outcomes in some urban streams. Other actions that may contribute to urban stream restoration goals include an integrated catchment approach to resolving fish passage issues, active reintroduction of wood to streams to enhance cover and habitat heterogeneity, and seeding of depauperate streams with native migratory fish to help initiate natural recolonisation.

1. Invertebrate drift patterns in a regulated river: dams, periphyton biomass or longitudinal patterns?
2009 – River Research and Applications
Jonathan D. Tonkin, Russell G. Death, Michael K. Joy

Macroinvertebrate drift was sampled at 15 sites along the Tongariro River, New Zealand above and below two hydroelectric dams. Sixty-seven invertebrate taxa were collected in the drift. Trichoptera (31) were the most diverse, followed by Diptera (13), Ephemeroptera (8) and Plecoptera (8). However, chironomidae were the numerically dominant taxa in the drift throughout the river and represented over 80% of all animals collected. Of these, Orthocladiinae and Diamesinae were the most abundant. Taxonomic richness declined with distance downstream and peaked at sites with intermediate levels of periphyton biomass. The per cent of Ephemeroptera, Plecoptera and Trichoptera (EPT) was 3–4 times higher in the unregulated section of the river and declined exponentially with both distance downstream and increase in periphyton biomass, but densities were similar along the river. Of the measured environmental variables periphyton biomass was most closely linked with drift community structure. Periphyton biomass was six times higher in the lower section of the river than the upper unregulated section. The autocorrelation between periphyton biomass and distance downstream complicates the interpretation of results. However, because of the distinct differences between above and below dam sections of river in periphyton biomass and the strong link between it and invertebrate drift we suggest that the alteration of flow patterns by the hydroelectric dams and the associated shift in periphyton biomass is the most likely explanation for invertebrate drift patterns in the river. Copyright # 2009 John Wiley & Sons, Ltd.

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