BIODIVERSITY AND PROBABLE ORIGINS OF THE MAYFLIES (EPHEMEROPTERA) OF THE SOUTHEASTERN UNITED STATES

M.L. Pescador, A.K. Rasmussen, and M.D. Hubbard. Entomology, Center for Water Quality, Florida A&M University, Tallahassee, FL 32307

There are approximately 300 mayfly species representing 60 genera known from the southeastern United States. The states with the most varied physiographic provinces appear to have higher mayfly diversity than the states that are confined to the Coastal Plain. A simple cluster analysis using Unweighted Pair Group Mathematical Averaging (UPGMA) was used to measure the similarities of the mayfly fauna of the various states in the region. The resultant dendogram showed three major clusters. The Coastal Plain states not only have a mayfly fauna of low diversity, but also have more species in common. Of the 20 families of mayflies represented in the Southeast, the Ephemerellidae, Heptageniidae, and Leptophlebiidae are the most diverse groups with species representing almost 50 percent of the total fauna. Endemicity is also high, representing approximately 30 percent of the region's fauna. The high diversity of the mayfly fauna of the Southeastern United States appears related to the geologic history, climatic conditions, and varied physiographic provinces of the region. The origin of the mayfly fauna of the region appears mainly boreal with a small amount of austral diffusion