Abstract
Nucleotide sequence analysis of a 238 base-pair segment of the mitochondrial control region for 392 Steller sea lions (Eumetopias jubatus) from rookeries across nearly the entire distributional range of the species supports the hypothesis of two genetically differentiated stocks. An eastern stock includes rookeries in California, Oregon, British Columbia, and southeastern Alaska. A western stock includes rookeries in Prince William Sound, the Bering Sea, Central Gulf of Alaska, Western Gulf of Alaska, Eastern Aleutian Islands, Central Aleutian Islands, Russia (Commander Islands and Kamchatka), and the Kuril Islands. The distribution of haplotypes and a phylogenetic analysis of the haplotypes provides evidence for the reconstruction of the evolutionary history of the populations. Steller sea lions diverged genetically as the result of being isolated in at least two, and possibly three, glacial refugia. The data indicate that females have a relatively high level of philopatry and the control region has a rapid rate of evolution, which has resulted in relatively high levels of haplotype endemism in some areas. In particular, the Kuril Islands appear to be highly variable with many low-frequency haplotypes unique to that area.
