Townsend Ted, Larson Allan, Louis Edward, Macey J Robert
Department of Biology, Washington University, St. Louis, Missouri 63130, USA.
Syst Biol. 2004 Oct;53(5):735-57. doi: 10.1080/10635150490522340.
Squamate reptiles (snakes, lizards, and amphisbaenians) serve as model systems for evolutionary studies of a variety of morphological and behavioral traits, and phylogeny is crucial to many generalizations derived from such studies. Specifically, the traditional dichotomy between Iguania (anoles, iguanas, chameleons, etc.) and Scleroglossa (skinks, geckos, snakes, etc.) has been correlated with major evolutionary shifts within Squamata. We present a molecular phylogenetic study of 69 squamate species using approximately 4600 (2876 parsimony-informative) base pairs (bp) of DNA sequence data from the nuclear genes RAG-1(approximately 2750 bp) and c-mos(approximately 360 bp) and the mitochondrial ND2 region (approximately 1500 bp), sampling all major clades and most major subclades. Under our hypothesis, species previously placed in Iguania, Anguimorpha, and almost all recognized squamate families form strongly supported monophyletic groups. However, species previously placed in Scleroglossa, Varanoidea, and several other higher taxa do not form monophyletic groups. Iguania, the traditional sister group of Scleroglossa, is actually highly nested within Scleroglossa. This unconventional rooting does not seem to be due to long-branch attraction, base composition biases among taxa, or convergence caused by similar selective forces acting on nonsister taxa. Studies of functional tongue morphology and feeding mode have contrasted the similar states found in Sphenodon(the nearest outgroup to squamates) and Iguania with those of Scleroglossa, but our findings suggest that similar states in Sphenodonand Iguania result from homoplasy. Snakes, amphisbaenians, and dibamid lizards, limbless forms whose phylogenetic positions historically have been impossible to place with confidence, are not grouped together and appear to have evolved this condition independently. Amphisbaenians are the sister group of lacertids, and dibamid lizards diverged early in squamate evolutionary history. Snakes are grouped with iguanians, lacertiforms, and anguimorphs, but are not nested within anguimorphs.
有鳞目爬行动物（蛇、蜥蜴和蚓蜥）是各种形态和行为特征进化研究的模式系统，系统发育对于从这类研究中得出的许多概括至关重要。具体而言，鬣蜥亚目（安乐蜥、鬣蜥、变色龙等）和硬舌亚目（石龙子、壁虎、蛇等）之间的传统二分法与有鳞目内部的主要进化转变相关。我们使用来自核基因RAG - 1（约2750碱基对）、c - mos（约360碱基对）以及线粒体ND2区域（约1500碱基对）的大约4600个（2876个简约信息）碱基对的DNA序列数据，对69种有鳞目物种进行了分子系统发育研究，涵盖了所有主要类群和大多数主要亚类群。在我们的假设下，先前归入鬣蜥亚目、蛇蜥亚目以及几乎所有公认的有鳞目科的物种形成了得到有力支持的单系类群。然而，先前归入硬舌亚目、巨蜥总科以及其他几个高级分类单元的物种并未形成单系类群。传统上作为硬舌亚目姐妹群的鬣蜥亚目，实际上高度嵌套在硬舌亚目之中。这种非常规的系统发育分支似乎并非由于长枝吸引、分类单元间的碱基组成偏差，或者作用于非姐妹分类单元的相似选择力导致的趋同现象。对功能性舌形态和进食模式的研究对比了喙头蜥（有鳞目最近的外类群）和鬣蜥亚目中发现的相似状态与硬舌亚目的状态，但我们的研究结果表明，喙头蜥和鬣蜥亚目中的相似状态是由平行进化导致的。蛇、蚓蜥和双足蜥，这些历史上系统发育位置一直难以确定的无肢形态，并未聚在一起，似乎是独立进化出这种状态的。蚓蜥是蜥蜴科的姐妹群，双足蜥在有鳞目进化历史早期就已分化。蛇与鬣蜥、蜥蜴形类和蛇蜥类聚在一起，但并不嵌套在蛇蜥类之中。
