Terrestrial invertebrates of dry river beds are not simply subsets of riparian assemblages
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Dry river beds are common worldwide and are rapidly increasing in extent due to the effects of water management and prolonged drought periods due to climate change. While attention has been given to the responses of aquatic invertebrates to drying rivers, few studies exist on the terrestrial invertebrates colonizing dry river beds. Dry river beds are physically harsh and they often differ substantially in substrate, topography, microclimate and inundation frequency from adjacent riparian zones. Given these differences, we predicted that dry river beds provide a unique habitat for terrestrial invertebrates, and that their assemblage composition differs from that in adjacent riparian zones. Dry river beds and riparian zones in Australia and Italy were sampled for terrestrial invertebrates with pitfall traps. Sites differed in substrate type, climate and flow regime. Dry river beds contained diverse invertebrate assemblages and their composition was consistently different from adjacent riparian zones, irrespective of substrate, climate or hydrology. Although some taxa were shared between dry river beds and riparian zones, 66 of 320 taxa occurred only in dry river beds. Differences were due to species turnover, rather than shifts in abundance, indicating that dry river bed assemblages are not simply subsets of riparian assemblages. Some spatial patterns in invertebrate assemblages were associated with environmental variables (irrespective of habitat type), but these associations were statistically weak. We suggest that dry river beds are unique habitats in their own right. We discuss potential human stressors and management issues regarding dry river beds and provide recommendations for future research.
KeywordsTemporary river Climate change Drought Riparian zone Community composition
AS was funded by the Queensland Department of Environment and Resource Management (DERM) and TRaCK (Tropical Rivers and Coastal Knowledge, http://www.track.gov.au). TRaCK received major funding for its research through the Australian Government’s Commonwealth Environment Research Facilities initiative; the Australian Government’s Raising National Water Standards Programme; Land and Water Australia and the Queensland Government’s Smart State Innovation Fund. Additional support was provided from the European Union through the Mediterranean Intermittent River ManAGEment (MIRAGE) project (ref: FP7 ENV 2007 1, http://www.mirage-project.eu). We acknowledge DERM for supplying the flow data for the Australian rivers, and IGB for supplying the flow data for the Tagliamento River. Diego Tonolla and Daniel von Schiller assisted with providing Tagliamento River GIS data. Many thanks to the field volunteers: in Australia—Jon and Jo Blessing, Sara Clifford, Ceaira Cottle, Werner Ehrsam, Jimmy Fawcett, Laurisse Frampton, Jess Haxen, Dean Holloway, Barry Kenway, Jaye Lobegeiger, Kate Masci, Morag McKinnon, Courtenay Mills, Annette Ritchie, Rob Rolls, Michael Rooke, Emily Saeck, Bill Senior, Suzanne Sippel, Ilva Sporne, Hamish Sutherland, Kenn Tews, Dominic Valdez, Ben Woodward, Belinda Young and Farah Zavahir; and in Italy—Claudio Cruciat and Brigitte Zoller. Thanks to Rob Rolls and Ben Stewart-Koster for providing statistical advice. We also wish to thank the landowners, particularly Neil and Helen Peddle. We thank the Australian Rivers Institute’s Aquatic Ecology Discussion Group (‘Dregs’) for providing comments on the manuscript. We thank Thibault Datry and the Guest Editor of this issue Dave Arscott. Finally we thank two anonymous referees for providing valuable criticism and excellent suggestions that greatly improved this manuscript.
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