Connecting stream communities

Posted on March 26, 2012

Although ecologists have traditionally treated natural communities more or less in isolation, there’s growing evidence that stream communities are structured by large-scale dispersal processes as well as local environmental conditions and species interactions.  A metacommunity is a set of local communities connected through the dispersal of potentially interacting species.  There’s been a recent flurry of interest in metacommunity theory, which accommodates the idea that the relative roles of local and regional factors vary with the spatial position in a river network because of trends in hydrology, stream form, disturbance and food resources between the headwaters and lower reaches.  Local and regional factors interact, for example as dispersing members of the regional species pool are filtered by local environmental tolerances and species interactions.  Constraints on dispersal set by the branching structure of streams can compromise population persistence and post-disturbance recovery in ways not found in other ecological systems.  Stream networks are different in other ways too – for example, compared to systems like lakes, forests and rock pools, river habitats tend to be less broken up into isolated patches, and population dispersal is often strongly directional as a result of water flow.  The ability of metapopulation theory to integrate processes at different spatial scales gives it the power to generate new insights into the structure and frunction of stream populations and ecosystems.

Reference:  Brown, B.L.  et al. 2011.  Metacommunity theory as a multispecies, multiscale framework for studying the influence of river network structure on riverine communities and ecosystems.  Journal of the North American Benthological Society 30(1), 310–327.