Caspers G J, Reinders G J, Leunissen J A, Wattel J, de Jong W W
Department of Biochemistry, University of Nijmegen, The Netherlands.
J Mol Evol. 1996 May;42(5):580-6. doi: 10.1007/BF02352288.
The phylogenetic relationships among the major groups of amniote vertebrates remain a matter of controversy. Various alternatives for the position of the turtles have been proposed, branching off either before or after the mammals. To discover the phylogenetic position of turtles in relation to mammals and birds, we have determined cDNA sequences for the eye lens proteins alpha A- and alpha B-crystallin of the red-eared slider turtle (Trachemys scripta elegans). In addition, databases were searched for turtle protein sequences, for which mammalian, avian, and outgroup orthologs were available. All sequences were analyzed by three phylogenetic tree reconstruction methods (neighbor-joining, maximum parsimony, and maximum likelihood). Including the alpha-crystallins, 7 out of 12 proteins support a sister-group relation of turtles and birds with all 3 methods. For each of the other five proteins no topology was consistently preferred by the three approaches. Analyses of the combined amino acid data (1,695 aligned sites) also give extremely strong evidence that turtles are nearer to birds, indicating that mammals branched off before the divergence between turtles and birds occurred.
羊膜动物主要类群之间的系统发育关系仍存在争议。关于龟类的分类地位，已提出了各种不同的观点，认为它们要么在哺乳动物之前分支，要么在哺乳动物之后分支。为了确定龟类相对于哺乳动物和鸟类的系统发育位置，我们测定了红耳龟（Trachemys scripta elegans）眼晶状体蛋白αA-和αB-晶状体蛋白的cDNA序列。此外，我们还在数据库中搜索了有哺乳动物、鸟类和外类群直系同源物的龟类蛋白质序列。所有序列均通过三种系统发育树重建方法（邻接法、最大简约法和最大似然法）进行分析。包括α-晶状体蛋白在内，12种蛋白质中有7种通过所有这三种方法都支持龟类和鸟类为姐妹群关系。对于其他五种蛋白质中的每一种，这三种方法都没有始终一致地偏好某一种拓扑结构。对组合氨基酸数据（1695个比对位点）的分析也提供了极其有力的证据，表明龟类比鸟类更接近，这意味着哺乳动物在龟类和鸟类分化之前就已经分支出去了。
