title: Balaenoptera omurai is a newly discovered baleen whale that represents an ancient evolutionary lineage.
abstract: Balaenoptera omurai, formerly classified as a small form of Bryde's whale, was recently reclassified as a new baleen whale species of the family Balaenopteridae. Although researchers have investigated the evolutionary history of Balaenopteridae and their relatives using molecular phylogenetic methods, the taxonomy of the ordinary Bryde's whale (Balaenoptera brydei) and small-form Bryde's whales (Balaenoptera edeni and B. omurai) remains unclear. We have used complete mtDNA sequences and short interspersed repetitive element (SINE) insertion patterns to construct the evolutionary history of both B. omurai and the taxonomically redefined species, B. edeni. The combined results demonstrate that B. omurai forms a monophyletic lineage with B. musculus, B. brydei, B. edeni and B. borealis and that B. omurai and B. musculus successively diverged from their common ancestor. In addition, we also showed that B. edeni constitutes a sister taxon to B. brydei. Our data suggest that B. omurai evolved as an ancient independent lineage that diverged much earlier than B. borealis, B. brydei and B. edeni, which were previously believed to be closely related to B. omurai.
authors.affiliation: Department of Evolutionary Biology and Biodiversity, National Institute for Basic Biology, 38 Nishigonaka, Myodaiji, Okazaki 444-8585, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sasaki
authors.forename: Masato
authors.initials: M
authors.lastname: Nikaido
authors.forename: Shiro
authors.initials: S
authors.lastname: Wada
authors.forename: Tadasu K
authors.initials: TK
authors.lastname: Yamada
authors.forename: Ying
authors.initials: Y
authors.lastname: Cao
authors.forename: Masami
authors.initials: M
authors.lastname: Hasegawa
authors.forename: Norihiro
authors.initials: N
authors.lastname: Okada
mesh_terms: D000818:Animals; D050616:Balaenoptera / Q000145:classification / Q000235:genetics / Q000502:physiology*; D004272:DNA, Mitochondrial; D008957:Models, Genetic; D010802:Phylogeny; D020086:Short Interspersed Nucleotide Elements
chemical_list: D004272:DNA, Mitochondrial