A molecular genetic approach to studying sylvatic plague on the landscape level: Testing black-tailed prairie dogs as major dispersers of plague.

摘要

I studied how the genetic structures of the black-tailed prairie dog, BTPD (Cynomys ludovicianus), its common flea species, Oropsylla hirsuta, and the plague bacterium, Yersinia pestis , overlapped in the prairie habitat in north-central Montana. This study took place during an unexpected epizootic which allowed the opportunity to assess how plague spreads between colonies.;I examined the population genetic structures of BTPDs and O. hirsuta to determine how their dispersal patterns impact the spread of Y. pestis. O. hirsuta revealed low genetic differentiation between the colonies which suggested their dispersal was unrestricted; patterns were consistent with a metapopulation model. For BTPDs, I primarily compared genetic structures of colonies treated with an insecticide, deltamethrin, over two years during the plague outbreak. The colonies exhibited changes in gene flow over both years indicating that plague can change the metapopulation dynamics of BTPDs. I also found no correlation between O. hirsuta allelic richness and gene diversity with plague prevalence suggesting that the increase in infected fleas during epizootics does not influence their population genetic structure.;In addition, I conducted microbial genetic studies of Y. pestis using Multilocus VNTR Analysis (MLVA) to further elucidate the genetic structure of Y. pestis isolated from infected fleas with the purpose of estimating its dispersal patterns among prairie dog colonies. A modified nested-MLVA approach was implemented; it allowed increased discrimination between closely-related strains. The results indicated transmission of plague between colonies was localized with some indication of long-distance dispersals. Lastly, I could not reliably forecast plague outbreaks based solely on Y. pestis prevalence on BTPD colonies.;I used microsatellite markers to estimate population genetic structures in both prairie dogs and O. hirsuta sampled from the same colonies. The results showed BTPDs were not the principal means of O. hirsuta dispersal; other species probably contributed to the spread of fleas between colonies.