Clonal diversity and polyphyletic origins of hybrid and spontaneous parthenogenetic Campeloma (Gastropoda : Viviparidae) from the south-eastern United States

Some theories for the maintenance of sexual reproduction indicate that part henogens may persist if there is high clonal diversity and high dispersal r ates. Using allozymic variation, we report on the origin, clonal diversity and population structure of hybrid and spontaneous parthenogens from southe astern United States populations of the freshwater snail Campeloma. Indepen dent origins of triploid hybrid parthenogens in the Florida panhandle occur red by hybridization between an Atlantic coastal species (C. limum or C. fl oridense) and the Florida sexual species (C. geniculum). Allozyme genotypic diversity is similar between these hybrid parthenogens and sexuals. Diploi d spontaneous parthenogens originated multiple times from nonlocal C. limum sexual populations in Atlantic coastal rivers, and levels of genotypic div ersity are significantly higher: in sexual C. limum. flow parthenogens orig inate, the degree of clonal diversity, and their subsequent dispersal influ ence whether basic assumptions of evolution-of-sex models are met.