Phylogeography and conservation genetics of the Iowa Pleistocene snail

The Iowa Pleistocene snail, Discus macclintocki, is an endangered species t hat survives only in relictual populations on algific (cold-air) talus slop es in northeast Iowa and northwest Illinois in the central region of the US A. These populations are believed to have been isolated since the temperatu res began to warm at the end of the last glacial period around 16 500 years ago. DNA sequencing of the 16s rRNA gene of the mitochondria was used to d etermine the genetic relationship among 10 populations and the genetic dive rsity within these populations. Genetic diversity is extremely high within this species with 40 haplotypes spread across the 10 populations sampled wi thin a 4000 km(2) region. Phylogenetic analyses showed that haplotypes form ed monophyletic groups by the watershed on which they were found, suggestin g that watersheds were important historical avenues of gene flow. Genetic d istances were strongly related to the geographical distance among all popul ations, but this relationship was dependent on the scale being considered.