Delsuc Frédéric, Tsagkogeorga Georgia, Lartillot Nicolas, Philippe Hervé
Institut des Sciences de l'Evolution, UMR5554-CNRS, Université Montpellier II, CC064, Place Eugène Bataillon, Montpellier Cedex 5, France.
Genesis. 2008 Nov;46(11):592-604. doi: 10.1002/dvg.20450.
Recent phylogenomic analyses have suggested tunicates instead of cephalochordates as the closest living relatives of vertebrates. In direct contradiction with the long accepted view of Euchordates, this new phylogenetic hypothesis for chordate evolution has been the object of some skepticism. We assembled an expanded phylogenomic dataset focused on deuterostomes. Maximum-likelihood using standard models and Bayesian phylogenetic analyses using the CAT site-heterogeneous mixture model of amino-acid replacement both provided unequivocal support for the sister-group relationship between tunicates and vertebrates (Olfactores). Chordates were recovered as monophyletic with cephalochordates as the most basal lineage. These results were robust to both gene sampling and missing data. New analyses of ribosomal rRNA also recovered Olfactores when compositional bias was alleviated. Despitethe inclusion of 25 taxa representing all major lineages, the monophyly of deuterostomes remained poorly supported. The implications of these phylogenetic results for interpreting chordate evolution are discussed in light of recent advances from evolutionary developmental biology and genomics.
最近的系统发育基因组分析表明，与脊椎动物亲缘关系最近的现存生物是被囊动物而非头索动物。这一关于脊索动物进化的新系统发育假说与长期以来被广泛接受的真脊索动物观点直接矛盾，引发了一些质疑。我们构建了一个扩展的系统发育基因组数据集，重点关注后口动物。使用标准模型的最大似然法以及使用氨基酸替换的CAT位点异质混合模型的贝叶斯系统发育分析，都明确支持了被囊动物和脊椎动物（嗅球类）之间的姐妹群关系。脊索动物被确认为单系类群，头索动物是最基部的谱系。这些结果对于基因抽样和缺失数据都很稳健。当成分偏差得到缓解时，对核糖体rRNA的新分析也得出了嗅球类。尽管纳入了代表所有主要谱系的25个分类单元，但后口动物的单系性仍然缺乏有力支持。结合进化发育生物学和基因组学的最新进展，讨论了这些系统发育结果对解释脊索动物进化的意义。
