Although migration occurs in many communities and theoretical studies suggest that it can be an important influence on community dynamics, it is not well understood. Stream communities provide an excellent opportunity to investigate migration. Recent research suggests that movement may be influenced by intraspecific and interspecific competition such that it is density-dependent. However, the prevalence of biotically induced migration in these communities is unknown. A few theoretical studies suggest that density-dependent migration can have important consequences for community dynamics; however, no thorough investigations have been undertaken. It is clear that both empirical and theoretical investigations are needed to understand not only the prevalence of density-dependent migration in streams, but its importance to community structure. A combination of laboratory and field experiments will be used to quantify the effects of environmental heterogeneity and intraspecific competition on the migration of a caddisfly, Hydropsyche slossonae. Laboratory studies will document processes and field studies will verify their importance in natural communities. Existing theoretical models will be modified to incorporate density-dependent migration. Through this modeling effort, the influence of such migration on community structure will be assessed. A computer model to will also be used to generate predictions specific to stream communities. Combining both empirical and theoretical studies will provide a unique opportunity to understand the influence of migration on population dynamics.
