title: Mitochondrial phylogenetics and evolution of mysticete whales.
abstract: The phylogenetic relationships among baleen whales (Order: Cetacea) remain uncertain despite extensive research in cetacean molecular phylogenetics and a potential morphological sample size of over 2 million animals harvested. Questions remain regarding the number of species and the monophyly of genera, as well as higher order relationships. Here, we approach mysticete phylogeny with complete mitochondrial genome sequence analysis. We determined complete mtDNA sequences of 10 extant Mysticeti species, inferred their phylogenetic relationships, and estimated node divergence times. The mtDNA sequence analysis concurs with previous molecular studies in the ordering of the principal branches, with Balaenidae (right whales) as sister to all other mysticetes base, followed by Neobalaenidae (pygmy right whale), Eschrichtiidae (gray whale), and finally Balaenopteridae (rorquals + humpback whale). The mtDNA analysis further suggests that four lineages exist within the clade of Eschrichtiidae + Balaenopteridae, including a sister relationship between the humpback and fin whales, and a monophyletic group formed by the blue, sei, and Bryde's whales, each of which represents a newly recognized phylogenetic relationship in Mysticeti. We also estimated the divergence times of all extant mysticete species, accounting for evolutionary rate heterogeneity among lineages. When the mtDNA divergence estimates are compared with the mysticete fossil record, several lineages have molecular divergence estimates strikingly older than indicated by paleontological data. We suggest this discrepancy reflects both a large amount of ancestral polymorphism and long generation times of ancestral baleen whale populations.
authors.affiliation: Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku Yokohama, Kanagawa 226-8501, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sasaki
authors.forename: Masato
authors.initials: M
authors.lastname: Nikaido
authors.forename: Healy
authors.initials: H
authors.lastname: Hamilton
authors.forename: Mutsuo
authors.initials: M
authors.lastname: Goto
authors.forename: Hidehiro
authors.initials: H
authors.lastname: Kato
authors.forename: Naohisa
authors.initials: N
authors.lastname: Kanda
authors.forename: Luis
authors.initials: L
authors.lastname: Pastene
authors.forename: Ying
authors.initials: Y
authors.lastname: Cao
authors.forename: R
authors.initials: R
authors.lastname: Fordyce
authors.forename: Masami
authors.initials: M
authors.lastname: Hasegawa
authors.forename: Norihiro
authors.initials: N
authors.lastname: Okada
mesh_terms: D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D004272:DNA, Mitochondrial / Q000235:genetics*; D019143:Evolution, Molecular; D016013:Likelihood Functions; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D014907:Whales / Q000145:classification / Q000235:genetics*
chemical_list: D017931:DNA Primers; D004272:DNA, Mitochondrial