FLEAS OF THE AMERICAN PIKA: DIVERSITY AND BIOGEOGRAPHY IN NORTH AMERICA’S INTERMOUNTAIN WEST

American pikas (Ochotona princeps) are small mammals that are widely distributed across North America’s Intermountain West. Previous investigations revealed five geographically distinct mitochondrial lineages within O. princeps associated with different mountain systems of the Intermountain West. In contrast, diversity of endoparasitic helminths of pikas is not structured geographically in the same way. Instead, there are two primary parasite assemblages, one distributed across southwestern pika populations and one found across the northeastern part of the host range. These contrasting patterns suggest that the shared history of pikas and their parasites had different consequences for the evolutionary trajectories of these organisms. Here I investigate whether or not patterns in diversity of fleas associated with pikas suggest a history that is more similar to that of the host or that of the endoparasites. I characterized the flea diversity and distribution within American pikas based on a sample of 837 flea specimens collected from 34 localities in the Intermountain West. I identified 11 flea species, two of which are common and known to be specific to pikas. I examined the population genetic structure of the most common flea species, Ctenophyllus armatus, for phylogeographic concordance between host and parasite diversity. I generated DNA sequences from the mitochondrial COII gene for 71 fleas representing 24 localities and showed general congruence between the phylogeographic structure of the fleas and that of the endoparasites. This is consistent with post-glacial pika population movements from temperate latitude mountain systems northward into the Coast, Cascade, and Rocky Mountain Ranges of Canada