BIODIVERSITY OF STREAM INSECTS - VARIATION AT LOCAL, BASIN, AND REGIONAL SCALES

We review the major conceptual developments that have occurred over th e last 50 years concerning the factors that influence insect biodivers ity in streams and examine how well empirical descriptions and theory match. Stream insects appear to respond to both spatial and temporal v ariation in physical heterogeneity. At all spatial scales, the data la rgely support the idea that physical complexity promotes biological ri chness, although exceptions to this relationship were found. These exc eptions may be related to how we measure habitat complexity at finer s patial scales and to factors that influence regional richness, such as biogeographic history, at broader spatial scales. However, the degree to which local stream insect assemblages are influenced by regional p rocesses is largely unknown.