HIGH VARIABILITY FOR CONTROL-REGION SEQUENCES IN A MARINE MAMMAL - IMPLICATIONS FOR CONSERVATION AND BIOGEOGRAPHY OF STELLER SEA LIONS (EUMETOPIAS-JUBATUS)

The Steller sea lion (Eumetopias jubatus) is a threatened species that has experienced significant population declines over the past 3 decad es. Previous genetic studies indicated low allozymic variability in th is monotypic species. However, high levels of variation exist in the m itochondrial control-region, as revealed by a 238 base-pair sequence f rom 224 specimens taken over most of the range of the species. Pattern s of macrogeographic variation indicate the presence of two geneticall y differentiated populations of Steller sea lions. A western populatio n included rookeries from the Commander Islands in Russia and the Aleu tian Islands and Gulf of Alaska in Alaska. An eastern population inclu ded rookeries from southeastern Alaska and Oregon. Phenetic analysis o f the mitochondrial-DNA (mtDNA) haplotypes indicates that certain hapl otype lineages are specific to one or the other populations. Thus, the se populations have been separated for a sufficient amount of time to allow diversification of lineages. However, the two populations are pa raphyletic with respect to mtDNA, which indicates that they do not tra ce their ancestries back to a single maternal ancestor in either case. The populations likely diverged as a result of separation in differen t glacial refugia.