Janke A, Erpenbeck D, Nilsson M, Arnason U
Department of Genetics, University of Lund, Sweden.
Proc Biol Sci. 2001 Mar 22;268(1467):623-31. doi: 10.1098/rspb.2000.1402.
The complete mitochondrial genomes of two reptiles, the common iguana (Iguana iguana) and the caiman (Caiman crocodylus), were sequenced in order to investigate phylogenetic questions of tetrapod evolution. The addition of the two species allows analysis of reptilian relationships using data sets other than those including only fast-evolving species. The crocodilian mitochondrial genomes seem to have evolved generally at a higher rate than those of other vertebrates. Phylogenetic analyses of 2889 amino-acid sites from 35 mitochondrial genomes supported the bird-crocodile relationship, lending no support to the Haematotherma hypothesis (with birds and mammals representing sister groups). The analyses corroborated the view that turtles are at the base of the bird-crocodile branch. This position of the turtles makes Diapsida paraphyletic. The origin of the squamates was estimated at 294 million years (Myr) ago and that of the turtles at 278 Myr ago. Phylogenetic analysis of mammalian relationships using the additional outgroups corroborated the Marsupionta hypothesis, which joins the monotremes and the marsupials to the exclusion of the eutherians.
为了研究四足动物进化的系统发育问题，对两种爬行动物——绿鬣蜥（Iguana iguana）和凯门鳄（Caiman crocodylus）的完整线粒体基因组进行了测序。这两个物种的加入使得能够使用除仅包含快速进化物种的数据集之外的其他数据集来分析爬行动物之间的关系。鳄鱼的线粒体基因组似乎总体上比其他脊椎动物进化得更快。对来自35个线粒体基因组的2889个氨基酸位点进行的系统发育分析支持了鸟类 - 鳄鱼的关系，不支持热血动物假说（鸟类和哺乳动物为姐妹群）。分析证实了龟类处于鸟类 - 鳄鱼分支基部的观点。龟类的这一位置使得双孔亚纲成为并系群。有鳞目动物的起源估计在2.94亿年前，龟类的起源在2.78亿年前。使用额外外类群对哺乳动物关系进行的系统发育分析证实了有袋总目假说，该假说将单孔目动物和有袋动物归为一类，排除了真兽类。
