Genetic structure and diversity among brook trout from Isle Royale, Lake Nipigon, and three Minnesota tributaries of Lake Superior

Brook trout Salvelinus fontinalis from Isle Royale, Michigan, three Minnesota tributaries of Lake Superior, and Lake Nipigon in Ontario were analyzed for genetic variation at 12 microsatellite DNA loci. Analysis of molecular variance, genetic distance measures, and cluster analysis were used to examine the diversity, gene flow, and relatedness among the samples. The diversity estimates for the samples from Isle Royale were similar to those for the samples collected from Minnesota tributaries of Lake Superior, and all estimates were lower than those reported in other studies of brook trout from eastern North America. Genetic differences were detected among the brook trout at Isle Royale, Lake Nipigon, and the Minnesota tributaries of Lake Superior. Further, the population in Tobin Harbor at the eastern end of Isle Royale was distinct from the populations from tributaries at the southwestern end of the island. The Minnesota tributary population formed a group that was genetically distinct from those from Isle Royale and Lake Nipigon. The Isle Royale population should be managed to preserve the genetic and phenotypic variation that distinguishes it from the other brook trout populations analyzed to date.