Distribution of hyporheic cyclopoids (Crustacea : Copepoda) in the easternUnited States

We sampled the hyporheic cyclopoid copepods of 14 unpolluted sites in the e astern United States to test whether community composition differed between glaciated and unglaciated sites. We found 31 species of cyclopoids in all, over half of which were new to science or only recently described. All of these newly discovered species were interstitial specialists ("stygobionts" ) living in the unglaciated Southeast, suggesting that many new species of hyporheic cyclopoids remain to be found in this region. Glaciated sites con tained fewer species of interstitial specialists (but not fewer species of generalists) and fewer narrowly endemic species than unglaciated sites. Fur ther, ordination results suggest that there is a break in species compositi on near the glacial border. In contrast, local ecological conditions had mu ch weaker effects on species composition. We also found strong differences between interstitial specialists and generalists in local distributions wit hin our study sites and in range size-abundance relationships. Our results thus show that glaciation has strong residual effects on the composition of present-day communities of hyporheic cyclopoids.