The influence of riverine network structure on patterns of benthic macroinvertebrate diversity and community structure

There is a growing appreciation that regional processes (i.e., dispersal driven processes) can influence diversity and community structure in ecological systems as much as local processes (environmental parameters, species interactions, speciation). In riverine macroinvertebrate systems, understanding these dispersal-driven influences necessarily involves additional complexities because of some of the unique features of these systems including the network-style construction of riverine dispersal networks, and organisms with life stages that allow dispersal outside of the riverine network (e.g., the adult flying stages of stream insects). However, understanding the forces that structure riverine communities may necessarily require some understanding of how dispersal drives diversity and community processes. We investigated the influence of dispersal-driven dynamics on diversity and community structure in benthic invertebrate communities using several datasets: the South Carolina Stream Assessment macroinvertebrate survey, the Maryland Biological Stream Survey, and personally collected data from Kings Mountain National Military Park, S.C., and Fort Jackson, S.C. We focused on two primary questions. 1) Do forces influencing diversity and structuring communities change with location within riverine networks? 2) Do similar patterns persist across systems? Ultimately we discovered that the relative influence of local and regional effects does shift with the position of local communities in riverine networks. However, the degree and nature of these shifts varied across systems, suggesting that though network structure matters, exactly how it matters depends on the specifics of the system of interest.