Journal article

Does dispersal control population densities in advection-dominated systems? A fresh look at critical assumptions and a direct test

Barbara J Downes, Jill Lancaster



1. In advection-dominated systems (both freshwater and marine), population dynamics are usually presumed to be dominated by the effects of migrants dispersing by advection, especially over the small spatial scales at which populations can be studied, but few studies have tested this presumption. We tested the hypothesis that benthic densities are controlled by densities of dispersers for two aquatic insects in upland streams. 2. Our study animals were two species of caddisflies (Hydropsychidae), which become sedentary filter-feeders following settlement onto substrata. Densities of dispersers in the drift (advective dispersal) were quantified using nets placed along the upstream edges of rif..

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Funding Acknowledgements

This work was supported by a Discovery Grant from the Australian Research Council to BJD. We thank Jodie Street, David Ryan, Andrew Sharpe, Paul Reich and many part-time research assistants for carrying out fieldwork. Jodie Street and Andrew Sharpe processed samples and produced some of the analytical results reported here. We thank Goran Englund for some constructive, critical remarks about the data. The manuscript was improved by comments from the freshwater ecology research group at the University of Melbourne: Nicole Barbee, Jane Catford, Rob Hale, Ash Macqueen and Deb Thomas, and we thank two referees for their constructive comments.