The Mitochondrial Genome of the Sperm Whale and a New Molecular Reference for Estimating Eutherian Divergence Dates |
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Authors: | Ulfur Arnason Anette Gullberg Solveig Gretarsdottir Björn Ursing Axel Janke |
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Institution: | Department of Genetics, Division of Evolutionary Molecular Systematics, University of Lund, S?lvegatan 29, S-223 62 Lund, Sweden, SE
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Abstract: | Extant cetaceans are systematically divided into two suborders: Mysticeti (baleen whales) and Odontoceti (toothed whales).
In this study, we have sequenced the complete mitochondrial (mt) genome of an odontocete, the sperm whale (Physeter macrocephalus), and included it in phylogenetic analyses together with the previously sequenced complete mtDNAs of two mysticetes (the
fin and blue whales) and a number of other mammals, including five artiodactyls (the hippopotamus, cow, sheep, alpaca, and
pig). The most strongly supported cetartiodactyl relationship was: outgroup,((pig, alpaca),((cow, sheep),(hippopotamus,(sperm
whale,(baleen whales))))). As in previous analyses of complete mtDNAs, the sister-group relationship between the hippopotamus
and the whales received strong support, making both Artiodactyla and Suiformes (pigs, peccaries, and hippopotamuses) paraphyletic.
In addition, the analyses identified a sister-group relationship between Suina (the pig) and Tylopoda (the alpaca), although
this relationship was not strongly supported. The paleontological records of both mysticetes and odontocetes extend into the
Oligocene, suggesting that the mysticete and odontocete lineages diverged 32–34 million years before present (MYBP). Use of
this divergence date and the complete mtDNAs of the sperm whale and the two baleen whales allowed the establishment of a new
molecular reference, O/M-33, for dating other eutherian divergences. There was a general consistency between O/M-33 and the
two previously established eutherian references, A/C-60 and E/R-50. Cetacean (whale) origin, i.e., the divergence between
the hippopotamus and the cetaceans, was dated to ≈55 MYBP, while basal artiodactyl divergences were dated to ≥65 MYBP. Molecular
estimates of Tertiary eutherian divergences were consistent with the fossil record.
Received: 12 July 1999 / Accepted: 28 February 2000 |
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Keywords: | : Molecular references — Cetferungulata — Cetartiodactyla — Cetancodonta — Cetacea — Mysticeti — Odontoceti — Sperm whale |
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