Microgeographic population genetic structure in the northern water snake, Nerodia sipedon sipedon detected using microsatellite DNA loci

We describe the isolation and genetic characterization of eight microsatell ite DNA loci from the northern water snake, Nerodia sipedon sipedon and use these loci to analyse levels of genetic differentiation between local (< 2 km apart) populations of these snakes in Ontario. These loci are variable, with expected heterozygosities ranging from 0.28 to 0.91, and can correctl y exclude nonsires in parentage analyses with a high probability (0.998). P opulation analyses reveal significant deviation from expected heterozygosit y levels for one population, probably a result of a null allele(s) at a sin gle locus and small but significant levels of genetic differentiation among all three populations. This demonstrates that microgeographic genetic stru cture exists in this species, possibly due to limited dispersal.