Higher level phylogeny of baleen whales

Abstract

Abstract The phylogenetic history of the bowhead whale (Balaena mysticetus) has been investigated intensively using ever-increasing samples of molecular data. By integrating this genomic information with evidence from the fossil record, divergence times can be estimated using “molecular clock” models. Recent hypotheses of cetacean phylogeny place the bowhead within Mysticeti (baleen whales), sister to the genus Eubalaena (North Atlantic, North Pacific, and southern right whales) in the family Balaenidae. The pygmy right whale (Caperea; Neobalaenidae) does not cluster with the skim-feeding balaenids and is instead positioned sister to Balaenopteroidea (rorquals and gray whale). Although a consensus has emerged regarding the divergence time between Mysticeti and Odontoceti (toothed whales) at ~36–39\xa0Ma in the latest Eocene, the timing of evolutionary splits within Mysticeti remain contentious. Accurate dating of the baleen whale tree is complicated by lineage-specific rates of molecular evolution, gene flow among distantly related mysticete taxa, as well as contradictory results when different data and methodological approaches are applied.