Hierarchical patterns of genetic population structure in black rat snakes (Elaphe obsoleta obsoleta) as revealed by microsatellite DNA analysis

investigated the distribution of variation at six microsatellite loci in th e black rat snake (Elaphe obsoleta obsoleta). Sampling occurred at three hi erarchical scales ranging from communal hibernacula to regional populations , with most locales situated within the Frontenac Axis region of eastern On tario. We detected no statistically significant pairwise differentiation (F -ST and R-ST) between hibernacula within the same subpopulations (interhibe rnaculum distance <6 km). However, isolation-by-distance was evident among locales within the Frontenac Axis (maximum of 50 km) and among regional pop ulations (maximum of 1500 km). Conservative estimates of N-e derived from h eterozygosity values ranged from approximately 600 to 2000. These values su ggest relatively large genetic neighborhoods encompassing many communal hib ernacula. Our results considered together suggest viscosity of gene flow ov er relatively short distances (tens of kilometers), but substantial genetic exchange among local hibernacula.