MOLECULAR PHYLOGENY OF MOBILE RIVER DRAINAGE-BASIN PLEUROCERID SNAILS(CAENOGASTROPODA, CERITHIOIDEA)

Sequences from the mitochondrial 16S rRNA gene were obtained to constr uct a molecular phylogeny for Mobile River drainage basin pleurocerid snails. Data from 876 aligned positions generated a single most-parsim onious tree for each of three analytical approaches: (1) equal weighti ng, (2) transversions weighted 2x transitions; and (3) transversions w eighted 4x transitions. Identical topologies for the resulting trees d epict the genera Elimia and Pleurocera as monophyletic sister taxa. Th e genus Leptoxis is paraphyletic with Leptoxis plicata sister to the E limia + Pleurocera clade. L. taeniata and L. ampla are sister taxa and L. picta is the most basal pleurocerid examined. When transversions w ere weighted 10x transitions a single most-parsimonious tree was obtai ned with the only topological difference being L. picta depicted as si ster to L. taeniata and L. ampla and L. plicata is now the most basal pleurocerid examined. Many of the Elimia species are closely related, but we await further data before making any taxonomic recommendations. L. picta and L. plicata are quite distinct from each other and all ot her pleurocerid species examined. These data serves as an important fo undation for future studies examining conservation genetics and system atics of this diverse and imperiled family. (C) 1997 Academic Press.