Amy M. Runck
Pleistocene events had a significant impact on the extinction of high latitude organisms. Southeast Alaska is a recently deglaciated region that has been colonized by two species of red-backed voles, Clethrionomys rutilus and C. gapperi. A contact zone near the Stikine River has been hypothesized and I have examined variation in the mitochondrial cytochrome b gene, the MYH2 nuclear intron, and the post palatal bridge. Low, but consistent, levels of sequence divergence of the cytochrome b gene were found among four endemic populations corroborating subspecific designations. Introgression of the mitochondrial genome diagnostic of C. rutilus was observed extending 80 km south of the Stikine River area in specimens of C. gapperi. Post glacial contact resulting from the retreat of the Cordilleran and Laurentide ice sheets has apparently led to the formation of this hybrid zone.