Biol. Rev. (2018), pp. 000–000. 1 doi: 10.1111/brv.12458 Reintroduction of freshwater macroinvertebrates: challenges and opportunities Jonas Jourdan1,∗ , Martin Plath2, Jonathan D. Tonkin3 , Maria Ceylan1, Arlena C. Dumeier4, Georg Gellert5, Wolfram Graf6, Charles P. Hawkins7, Ellen Kiel4, Armin W. Lorenz8, Christoph D. Matthaei9, Piet F. M. Verdonschot10,11, Ralf C. M. Verdonschot10 and Peter Haase1,12 1Department of River Ecology and Conservation, Senckenberg Research Institute and Natural History Museum Frankfurt, Clamecystr. 12, 63571 Gelnhausen, Germany 2Shaanxi Key Laboratory for Molecular Biology in Agriculture and College of Animal Science and Technology, Northwest A&F University, Xinong Road 22, Yangling, 712100 Shaanxi, China 3Department of Integrative Biology, Oregon State University, Corvallis, 3029 Cordley Hall, OR 97331, U.S.A. 4Department of Biology and Environmental Sciences – Aquatic Ecology and Nature Conservation, Carl von Ossietzky University of Oldenburg, Ammerl¨ander Heerstr. 114–118, 26129 Oldenburg, Germany 5Landesarbeitskreis Wasser, Bund f¨ur Umwelt und Naturschutz Deutschland Landesverband Nordrhein-Westfalen, Merowingerstr. 88, 40225 D¨usseldorf, Germany 6Institute of Hydrobiology and Aquatic Ecosystem Management, BOKU - University of Natural Resources and Life Sciences, Gregor-Mendel-Straße 33, 1180, Vienna, Austria 7Department of Watershed Sciences, National Aquatic Monitoring Center, and Ecology Center, Utah State University, 5210 Old Main Hill, Logan, UT 84322-5210, U.S.A. 8Department of Aquatic Ecology, Faculty of Biology, University of Duisburg-Essen, Universit¨atsstr. 5, 45141 Essen, Germany 9Department of Zoology, University of Otago, 340 Great King Street, Dunedin 9016, New Zealand 10Wageningen Environmental Research, Wageningen University and Research, Droevendaalsesteeg 3, 6700AA Wageningen, The Netherlands 11Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Science Park 904, 1090GE Amsterdam, The Netherlands 12Faculty of Biology, University of Duisburg-Essen, Universit¨atsstr. 5, 45141 Essen, Germany ABSTRACT 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. Key words: invertebrate reintroduction, conservation, translocation, species management, population restoration, restoring diversity. * Address for correspondence (Tel: +49 6051 61954 3125; E-mail: [email protected]) Biological Reviews (2018) 000–000 © 2018 Cambridge Philosophical Society 2 Jonas Jourdan and others CONTENTS I. Introduction .............................................................................................. 2 II. Reviewing methods ...................................................................................... 3 III. Current status of freshwater macroinvertebrate reintroductions .......................................... 4 (1) Reintroduction of non-insect species ................................................................. 4 (2) Reintroduction of aquatic and semi-aquatic insects .................................................. 8 IV. Factors determining the success of reintroductions ....................................................... 8 (1) Intrinsic factors ....................................................................................... 9 (a) Effects of life cycles ................................................................................ 9 (b) Life-history differences ............................................................................ 10 (c) Standing genetic variation and evolvability ....................................................... 10 (d) Phenotypic plasticity .............................................................................. 11 (e) Signatures of local adaptation ..................................................................... 11 (f ) Behavioural deficiencies .......................................................................... 11 (2) Extrinsic factors ...................................................................................... 11 (a) Water quality ..................................................................................... 11 (b) Microhabitat availability .......................................................................... 12 (c) Timing of reintroduction ......................................................................... 12 (d) Competition, predation and facilitation ........................................................... 12 (e) Handling effects during release ................................................................... 13 V. Risks and opportunities of macroinvertebrate reintroductions ........................................... 13 (1) Translocation of pathogens and invasive species ..................................................... 13 (2) Significance of the evolutionary history of species and populations ................................... 13 (3) Opportunities ........................................................................................ 14 VI. Recommendations for practitioners ...................................................................... 14 (1) Planning the reintroduction .......................................................................... 14 (2) Selection of target species and populations ........................................................... 14 (3) Avoiding pathogen and parasite transmission ........................................................ 15 (4) Post-reintroduction monitoring ....................................................................... 15 VII. Conclusions .............................................................................................. 16 VIII. Acknowledgements ....................................................................................... 16 IX. References ................................................................................................ 16 I. INTRODUCTION functional traits (Palmer, Ambrose & Poff, 1997). Although subsequent evaluations often confirm an improvement in Humans have profoundly altered freshwater ecosystems physico-chemical conditions and macro-scale morphological by overexploitation, habitat degradation, and pollution, habitat quality (Palmer et al., 2010), these improvements all of which have contributed to the decline of native have rarely achieved the desired outcome for the aquatic biodiversity (Allan & Flecker, 1993; Dudgeon et al., 2006). community (Palmer et al., 2010; Haase et al., 2013). Benthic In recent decades, there has been increasing emphasis macroinvertebrates, in particular, often show no substantial on the restoration of freshwater ecosystems worldwide increase in population densities, species richness or trait (Palmer, Menninger & Bernhardt, 2010; Haase et al., 2013; diversity in response to restoration activities (Palmer et al., Palmer, Hondula & Koch, 2014). Broad policy initiatives 2010; Louhi et al., 2011; Pilotto et al., in press). aiming at protecting aquatic life (e.g. the Water Framework Multiple factors may inhibit macroinvertebrate recoloni- Directive 2000/60/EC in Europe, or the Clean Water Act in sation following restoration, including deficiencies in water the USA) have resulted in the widespread implementation quality (Kail, Arle & Jahnig,¨ 2012) associated with catchment of restoration with substantial financial costs (Bernhardt land use (Harding et al., 1998). In cases where water quality is et al., 2005). Often, projects have focused on restoring good and the aquatic habitat attains a pre-disturbance state, hydromorphological and physico-chemical properties of dispersal and metapopulation dynamics play a significant freshwater habitats [e.g. hydromorphological conditions role in determining recolonisation success (Clarke et al., 2008; (Bernhardt et al., 2005), chemical pollutants (Skjelkvale˚ et al., Tonkin et al., 2014; Li et al., 2016). Freshwater macroinverte- 2005)] or hydrological regimes of wetlands (Zedler, 2000), brates use a variety of active (e.g. upstream movement, aerial driven by the assumption that habitat improvement will dispersal) and passive (e.g. downstream drift, bird-mediated lead to a corresponding restoration of previous species dispersal) mechanisms to colonise