MITOCHONDRIAL-DNA VARIATION AMONG SUBSPECIES AND POPULATIONS OF SEA OTTERS (ENHYDRA-LUTRIS)

We used restriction-enzyme analysis of polymerase-chain reaction-ampli fied, mitochondrial DNA (mtDNA) to assess genetic differentiation of s ubspecies and populations of sea otters, Enhydra lutris, throughout th e range of the species. There were several haplotypes of mtDNA in each subspecies and geographically separate populations. MtDNA sequence di vergence of haplotypes of sea otters was 0.0004-0.0041 base substituti ons per nucleotide. E. I. nereis appears to have monophyletic mitochon drial DNA, while E. I. lutris and E. I. kenyoni do not. Different freq uencies of haplotypes of mtDNA among populations reflect current restr iction of gene flow and the unique histories of different populations. There are two or three haplotypes of mtDNA and diversity of haplotype s is 0.1376-0.5854 in each population of otters. This is consistent wi th theoretical work, which suggests that population bottlenecks of sea otters probably did not result in major losses of genetic variation f or individual populations, or the species as a whole.