| Summary: | Recent biogeographic history in North America has been dominated by glacial- interglacial cycles. The repeated isolation and reconnection of populations of various taxa has had a profound impact on intraspecies diversity. Many formal classifications of this diversity used morphological traits, but these often confound with genetic data. As habitats become increasingly fragmented and populations become isolated, an understanding of subspecific diversity (e.g. ESUs) in threatened and endangered species is paramount to appropriate management intended to promote connectivity. Through analysis of mitochondrial DNA sequences and 14 microsatellite loci we elucidate the phylogeographic history of caribou (Rangifer tarandus) and reevaluate their classification in western North America. Results indicate important restructuring of caribou subspecies, their distribution and the designation of ecotypes. For example, the subspecies R.t. grantiof Alaska and R.t. groenlandicus of northern Canada show significant genetic diversity, reciprocal introgression and common ancestry, belying sufficient differentiation expected at the subspecies level. Conversely, the Northern Mountain ecotype of woodland caribou (R.t. caribou) appears to have closer kinship to caribou classified as grantiorgroenlandicusthan to woodland caribou. These results provide important insight into the evolutionary history of caribou in North America, and are important for managers evaluating source populations for caribou translocation conservation measures.
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