Genetics of Potamopyrgus antipodarum (Gastropoda: Prosobranchia): Variation in unisexual populations

The New Zealand gastropod Potamopyrgus antipodarum comprises both unisexual and bisexual populations. The aim of this study was to examine the genetic variation of unisexual populations and to determine whether the variation observed was consistent with the predictions of ameiotic or meiotic parthenogenesis. Genetic variation within and among eight unisexual populations of P. antipodarum (four from the Auckland region and four from the Rotorua region) was examined for seven presumptive loci. The results indicated extreme genetic divergence both within populations, among populations within each region, and between regions. In many instances a significant excess of heterozy gotes was noted, suggesting ameiotic parthenogenesis. The finding of genetic divergence within individual populations is not consistent with the one-clone one-population hypothesis generally postulated for ameiotic parthenogens. Possible origins of this variation are discussed.