title: Cytochrome b nucleotide sequences and the identification of five primary lineages of extant cetaceans.
abstract: Relationships among and within baleen and toothed whales were examined using the complete sequence of the mitochondrial cytochrome b gene. Based on parsimony analyses of conservative nucleotide substitutions, five primary evolutionary lineages of extant cetaceans were identified, one represented by baleen whales (Mysticeti) and four represented by odontocetes (toothed whales). Based on the most comprehensive representation of taxa, both cetaceans and artiodactyls, the most parsimonious relationship among the five lineages is (Mysticeti, Odontoceti (Platanistoidea (Physeteroidea (Ziphioidea (Delphinida))))). This relationship, however, is labile and sensitive to ingroup representation and the choice of outgroup. The short nodes among the five cetacean lineages suggest that the divergence among these lineages occurred over a narrow time period, a finding consistent with the limited fossil evidence that indicates a major cetacean radiation 30-34 Mya. The level of divergence among the five cetacean lineages, and that seen between cetaceans and artiodactyls, suggests that cetaceans and artiodactyls had a common ancestor approximately 60 Mya.
authors.affiliation: Division of Evolutionary Molecular Systematics, University of Lund, Sweden. Ulfur.Arnason@gen.lu.se
authors.forename: U
authors.initials: U
authors.lastname: Arnason
authors.forename: A
authors.initials: A
authors.lastname: Gullberg
mesh_terms: D000818:Animals; D001188:Artiodactyla / Q000235:genetics; D001483:Base Sequence; D002591:Cetacea / Q000145:classification / Q000235:genetics*; D003573:Cytochrome b Group / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics*; D004289:Dolphins / Q000145:classification / Q000235:genetics; D019143:Evolution, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D017354:Point Mutation; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity; D014907:Whales / Q000145:classification / Q000235:genetics
chemical_list: D003573:Cytochrome b Group; D004272:DNA, Mitochondrial