Phylogenetic relationships within the eared seals (Otariidae : Carnivora):Implications for the historical biogeography of the family

Phylogenetic relationships within the family Otariidae were investigated us ing two regions of the mitochondrial genome. A 360-bp region of the cytochr ome b gene was employed for the primary phylogenetic analysis, while a 356- bp segment of the control region was used to enhance resolution of the term inal nodes. Traditional classification of the family into the subfamilies A rctocephalinae (fur seals) and Otariinae (sea lions) is not supported, with the fur seal Callorhinus ursinus having a basal relationship relative to t he rest of the family. This is consistent with the fossil record which sugg ests that this genus diverged from the line leading to the remaining fur se als and sea lions about 6 million years ago (mya). There is also little evi dence to support or refute the monophyly of sea lions. Four sea lion clades and five far seal clades were observed, but relationships among these clad es are unclear. Similar genetic divergences between the sea lion clades (D- a = 0.054-0.078), as well as between the major Arctocephalus far seal clade s (D-a = 0.040-0.069) suggest that these groups underwent periods of rapid radiation at about the time they diverged from each other. Rapid radiations of this type make the resolution of relationships between the resulting sp ecies difficult and indicate the requirement for additional molecular data from both nuclear and mitochondrial genes. The phylogenetic relationships w ithin the family and the genetic distances among some taxa highlight incons istencies in the current taxonomic classification of the family. (C) 2001 A cademic Press.