Microgeographic variation in allozymes and mitochondrial DNA ofMicrotus richardsoni, the water vole, in the Beartooth Mountains of Montana and Wyoming, U.S.A.

Abstract

Microtus richardsoni, the water vole, is listed as a sensitive species within region 2 of the USDA Forest Service. Because it is a sensitive species, the water vole's ability to disperse becomes an important management concern in terms of its population viability. Both allozyme and mitochondrial DNA analyses were used to study microgeographic population structure within a group of populations from four adjacent watersheds of the Beartooth Mountains of Montana and Wyoming. Of 31 protein loci examined, only ADH, EST-1, and SOD-1 were polymorphic. ADH and EST-1 were in Hardy–Weinberg equilibrium, but SOD-1 was not. Mitochondrial DNA was found to be polymorphic with 9 restriction enzymes. The size of the fragments produced by each restriction enzyme was estimated and ordered into a site map. In total, 51 sites were found with 9 restriction enzymes resulting in 29 different haplotypes from 142 individuals. Shared haplotypes were geographically contiguous except for one. There was no significant difference in genetic distance among water voles from the Beartooth Mountains, and only the outgroup from Togwotee Pass in the Absaroka Mountains of Wyoming had significant genetic distance. This suggests the possibility of dispersal between water voles from the contiguous watersheds of the Beartooth Mountains but not between the Beartooth Mountains and Togwotee Pass populations.