Arnason U, Gullberg A, Gretarsdottir S, Ursing B, Janke A
Department of Genetics, Division of Evolutionary Molecular Systematics, University of Lund, Sölvegatan 29, S-223 62 Lund, Sweden.
J Mol Evol. 2000 Jun;50(6):569-78. doi: 10.1007/s002390010060.
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 approximately 55 MYBP, while basal artiodactyl divergences were dated to >/=65 MYBP. Molecular estimates of Tertiary eutherian divergences were consistent with the fossil record.
须鲸亚目（须鲸）和齿鲸亚目（齿鲸）。在本研究中，我们对一种齿鲸——抹香鲸（Physeter macrocephalus）的完整线粒体（mt）基因组进行了测序，并将其与之前测序的两种须鲸（长须鲸和蓝鲸）以及其他一些哺乳动物（包括五种偶蹄目动物：河马、牛、绵羊、羊驼和猪）的完整mtDNA一起纳入系统发育分析。得到最有力支持的鲸偶蹄类关系是：外类群，(((猪, 羊驼), ((牛, 绵羊),(河马,(抹香鲸,(须鲸))))))。与之前对完整mtDNA的分析一样，河马与鲸类之间的姐妹群关系得到了有力支持，这使得偶蹄目和猪形亚目（猪、西貒和河马）成为并系群。此外，分析确定了猪形亚目（猪）和胼足亚目（羊驼）之间的姐妹群关系，尽管这种关系没有得到有力支持。须鲸和齿鲸的古生物学记录可追溯到渐新世，这表明须鲸和齿鲸谱系在距今3200 - 3400万年前（MYBP）分化。利用这个分化时间以及抹香鲸和两种须鲸的完整mtDNA，建立了一个新的分子参考O/M - 33，用于确定其他真兽类分化的时间。O/M - 33与之前建立的两个真兽类参考A/C - 60和E/R - 50总体上是一致的。鲸类（鲸）的起源，即河马与鲸类之间的分化，可追溯到大约55 MYBP，而基础偶蹄目动物的分化时间可追溯到≥65 MYBP。第三纪真兽类分化的分子估计与化石记录一致。
