Lee M S Y
School of Earth and Environmental Sciences, University of Adelaide, Adelaide, SA, Australia.
J Evol Biol. 2009 Jun;22(6):1308-16. doi: 10.1111/j.1420-9101.2009.01751.x. Epub 2009 Apr 23.
A combined analysis of nuclear, mitochondrial and morphological data robustly resolves snakes as the sister taxon to anguimorph 'lizards'. Analysed in isolation, nuclear DNA (nDNA) produces a trichotomy between snakes, iguanians and anguimorphs, mitochondrial DNA (mtDNA) is largely uninformative at deeper levels, and morphology tends to nest snakes deep within anguimorphs or with various legless squamate groups. When analysed simultaneously, the nuclear signal is sufficiently strong that mtDNA and morphology are constrained to choose between alternative resolutions of the iguanian-anguimorph-snake trichotomy (generated by the nDNA) - and both support the snake-anguimorph solution. Combined analyses of fast-evolving or idiosyncratically evolving markers (mtNDA, morphology) with conservative traits (e.g. nuclear genes) might be the best way to resolve ancient, closely spaced divergences. Fast or idiosyncratic markers potentially provide the most information about short, ancient internodes, but can converge on spurious trees if analysed in isolation. However, if constrained to only choosing between plausible trees, such data can contribute unique and valuable phylogenetic signal that resolves such problematic divergences.
对核基因、线粒体基因和形态学数据的综合分析有力地确定了蛇是有鳞目蜥蜴亚目“蜥蜴”的姐妹分类群。单独分析时，核DNA（nDNA）在蛇、鬣蜥和有鳞目蜥蜴亚目之间产生了一个三分法，线粒体DNA（mtDNA）在更深层次上基本没有信息，而形态学倾向于将蛇嵌套在有鳞目蜥蜴亚目深处或与各种无腿有鳞类群在一起。同时分析时，核基因信号足够强大，以至于mtDNA和形态学被限制在鬣蜥 - 有鳞目蜥蜴亚目 - 蛇三分法的不同解析之间进行选择（由nDNA产生），并且两者都支持蛇 - 有鳞目蜥蜴亚目这一解析。将快速进化或特异进化的标记（mtNDA、形态学）与保守性状（如核基因）进行综合分析，可能是解决古老且间隔很近的分化问题的最佳方法。快速或特异的标记可能提供有关短的、古老的节间的最多信息，但如果单独分析可能会得出虚假的系统树。然而，如果限制在仅在合理的系统树之间进行选择，这样的数据可以提供独特且有价值的系统发育信号，从而解决此类有问题的分化。
