Population genetic structure of the prairie dog flea and plague vector, Oropsylla hirsuta

Oropsylla hirsuta is the primary flea of the black-tailed prairie dog and is a vector of the plague bacterium, Yersinia pestis. We examined the population genetic structure of O. hirsuta fleas collected from 11 prairie dog colonies, 7 of which had experienced a plague-associated die-off in 1994. In a sample of 332 O. hirsuta collected from 226 host individuals, we detected 24 unique haplotype sequences in a 480 nucleotide segment of the cytochrome oxidase II gene. We found significant overall population structure but we did not detect a signal of isolation by distance, suggesting thatO. hirsutamay be able to disperse relatively quickly at the scale of this study. All 7 colonies that were recently decimated by plague showed signs of recent population expansion, whereas 3 of the 4 plague-negative colonies showed haplotype patterns consistent with stable populations. These results suggest thatO. hirsuta populations are affected by plague-induced prairie dog die-offs and that flea dispersal among prairie dog colonies may not be dependent exclusively on dispersal of prairie dogs. Re-colonization following plague events from plague-free refugia may allow for rapid flea population expansion following plague epizootics.