DNA Barcoding Suggests Sexual and Asexual Campeloma decisum (Say, 1817) (Gastropoda: Viviparidae) are Different Taxa

Campeloma decisum (Say, 1817) is a species of freshwater snail found across the eastern United States. Populations of C. decisum may be sexual, with males and females present, or asexual containing only females. The distribution of population reproductive modes is thought to reflect asexual colonization following Pleistocene glaciation. Using Bayesian analysis of coxI gene sequences, our data suggest C. decisum represents at least two distinct taxa, with sexual populations related to other sexual Campeloma species and asexual populations related to other asexual Campeloma and the sexual C. geniculum. Our data further suggest this diversification occurred in the Miocene, with the geographical distinction between sexual and asexual populations being less reliant on glaciation than originally believed.