Vidal Nicolas, Hedges S Blair
Department of Biology, Astrobiology Research Center, Pennsylvania State University, University Park, PA 16802-5301, USA.
C R Biol. 2005 Oct-Nov;328(10-11):1000-8. doi: 10.1016/j.crvi.2005.10.001. Epub 2005 Oct 27.
Squamate reptiles number approximately 8000 living species and are a major component of the world's terrestrial vertebrate diversity. However, the established relationships of the higher-level groups have been questioned in recent molecular analyses. Here we expand the molecular data to include DNA sequences, totaling 6192 base pairs (bp), from nine nuclear protein-coding genes (C-mos, RAG1, RAG2, R35, HOXA13, JUN, alpha-enolase, amelogenin and MAFB) for 19 taxa representing all major lineages. Our phylogenetic analyses yield a largely resolved phylogeny that challenges previous morphological analyses and requires a new classification. The limbless dibamids are the most basal squamates. Of the remaining taxa (Bifurcata), the gekkonids form a basal lineage. The Unidentata, squamates that are neither dibamids nor gekkonids, are divided into the Scinciformata (scincids, xantusiids, and cordylids) and the Episquamata (remaining taxa). Episquamata includes Laterata (Teiformata, Lacertiformata, and Amphisbaenia, with the latter two joined in Lacertibaenia) and Toxicofera (iguanians, anguimorphs and snakes). Our results reject several previous hypotheses that identified either the varanids, or a burrowing lineage such as amphisbaenians or dibamids, as the closest relative of snakes. Our study also rejects the monophyly of both Scleroglossa and Autarchoglossa, because Iguania, a species-rich lineage (ca. 1440 sp.), is in a highly nested position rather than being basal among Squamata. Thus iguanians should not be viewed as representing a primitive state of squamate evolution but rather a specialized and successful clade combining lingual prehension, dependence on visual cues, and ambush foraging mode, and which feeds mainly on prey avoided by other squamates. Molecular time estimates show that the Triassic and Jurassic (from 250 to 150 Myr) were important times for squamate evolution and diversification.
有鳞目爬行动物现存约8000种，是世界陆地脊椎动物多样性的主要组成部分。然而，近期的分子分析对高级类群已确立的亲缘关系提出了质疑。在此，我们扩展了分子数据，纳入了来自9个核蛋白编码基因（C - mos、RAG1、RAG2、R35、HOXA13、JUN、α - 烯醇化酶、釉原蛋白和MAFB）的DNA序列，共计6192个碱基对（bp），涉及代表所有主要谱系的19个分类单元。我们的系统发育分析得出了一个基本解析清楚的系统发育树，这对先前的形态学分析提出了挑战，需要一个新的分类。无肢的双斑蛇科是最基部的有鳞目动物。在其余分类单元（双叉类）中，壁虎科形成一个基部谱系。单系类，即既不是双斑蛇科也不是壁虎科的有鳞目动物，分为石龙子类（石龙子科、黄蜥科和绳蜥科）和上鳞类（其余分类单元）。上鳞类包括后类（蜥蜴类、蜥蜴亚目和蚓蜥目，后两者合并为蜥蜴蚓蜥类）和毒蜥类（鬣蜥类、蛇蜥类和蛇类）。我们的结果否定了先前的几个假说，这些假说认为巨蜥类，或者像蚓蜥类或双斑蛇科这样的穴居谱系是蛇类的最近亲缘类群。我们的研究还否定了硬舌亚目和全舌亚目的单系性，因为鬣蜥类，一个物种丰富的谱系（约1440种），处于一个高度嵌套的位置，而不是在有鳞目基部。因此，鬣蜥类不应被视为代表有鳞目进化的原始状态，而应被视为一个特殊且成功的分支，它结合了舌抓握、依赖视觉线索和伏击觅食模式，并且主要以其他有鳞目动物避开的猎物为食。分子时间估计表明，三叠纪和侏罗纪（从2.5亿年前到1.5亿年前）是有鳞目进化和多样化的重要时期。
