An exploration of factors influencing lotic insect species richness

An understanding of factors that influence species richness of lotic insect s is generally lacking. We present comparative data on aquatic insect speci es richness from several North American and other streams. Factors such as large sample numbers and drainage area (species area relationships) are not significant predictors of species richness across the streams we examined. We explore several hypotheses regarding the origins and maintenance of spe cies richness using Upper Three Runs Creek (UTR), South Carolina, USA, as a reference stream. UTR has the highest species richness of any stream in th e Western Hemisphere. Hypotheses examined included historical, regional and local processes such as: (1) Evolutionary time, (2) disturbance regime/env ironmental variability, (3) temperature/evolutionary-speed, (4) productivit y, and (5) habitat heterogeneity. Of these hypotheses, we suggest that prod uctivity and habitat heterogeneity appear to contribute most to the high sp ecies richness found in UTR. We believe that multidisciplinary analysis of other streams is necessary because without this crucial information our kno wledge of, and desire to protect biodiversity in streams will be wanting.