Reindeer introgression and the population genetics of caribou in Southwestern Alaska

Alaska caribou (Rangifer tarandus granti) in southwestern Alaska are a poorly understood system, with differing descriptions of their regional population structure, population abundance that has varied greatly through time and instances of the release of domestic reindeer (R. t. tarandus) into their range. Here, we use 21 microsatellites and 297 individuals to investigate the genetic population structure of herds and examine for population bottlenecks. Then, using genetic characteristics of existing reindeer populations, we examine introgression into the wild caribou populations. Caribou of the area are genetically diverse (HE between 0.69 – 0.84), with diversity decreasing along the Alaska Peninsula (AP). Using GST and Jost’s D, we find extensive structuring among all herds; MIGRATE-N finds AP herds share few effective migrants with other herds, with South AP and Unimak Island herds having the least. Bayesian clustering techniques are able to resolve all but Denali and Mulchatna caribo...