LOW GENETIC-VARIATION AMONG KILLER WHALES (ORCINUS-ORCA) IN THE EASTERN NORTH PACIFIC AND GENETIC DIFFERENTIATION BETWEEN FORAGING SPECIALISTS

Killer whales from the coastal waters off California through Alaska we re compared for genetic variation at three nuclear DNA markers and seq uenced for a total of 520 bp from the mitochondrial control region. Tw o putative sympatric populations that range throughout this region wer e compared. They can be distinguished by social and foraging behavior and are known as ''residents'' and ''transients.'' We found low levels of variation within populations compared to other cetacean species. C omparisons between fish (resident) versus marine mammal (transient) fo raging specialists indicated highly significant genetic differentiatio n at both nuclear and mitochondrial loci. This differentiation is at a level consistent with intraspecific variation. A comparison between t wo parapatric resident populations showed a small but fixed mtDNA hapl otype difference. Together these data suggest low levels of genetic di spersal between foraging specialists and a pattern of genetic differen tiation consistent with matrifocal population structure and small effe ctive population size.