Genomic data do not support comb jellies as the sister group to all other animals
Genomic data do not support comb jellies as the sister group to all other animals
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DOI：
10.1073/pnas.1518127112
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发表时间：
2015-12-15
影响因子：
11.1
通讯作者：
Woerheide, Gert
中科院分区：
文献类型：
--
作者：
Pisani, Davide;Pett, Walker;Woerheide, Gert
了解复杂的特征，如上皮、神经系统、肌肉或肠道是如何起源的，取决于关于主要动物谱系之间的系统发育关系的一个得到充分支持的假说。传统上，海绵动物被解释为其余动物的姐妹群，这一假说与传统观点一致，即最后一个共同的动物祖先相对简单，更复杂的身体计划出现在进化的后期。然而，这一前提最近受到了对梳水母基因组的分析的挑战，相反，对梳水母的基因组分析发现，纤毛虫是其余动物的姊妹群(“纤毛目姐妹”假说)。因为鞭毛虫是形态复杂的捕食者，有真正的上皮、神经系统、肌肉和肠道，这种情况意味着这些特征要么存在于所有动物的最后一个共同祖先中，然后在海绵和胎盘动物(毛状虫)中消失，要么在梳状水母中收敛地进化。在这里，我们分析了来自最近支持Ctenophora-SISTER的研究的代表性数据集，包括串联蛋白质序列的基因组规模比对，以及基因组基因含量数据集。我们没有发现对Ctenophora-SISTER的支持，并得出结论，这是由于方法学不充分造成的人工制品，特别是使用简单化的进化模型和不适当的物种选择来扎根后生动物树。我们的结果强化了动物复杂性进化的传统假说，并表明基于Ctenophora-SISTER假说的后生动物进化的推断不被当前可用的数据支持。
Understanding how complex traits, such as epithelia, nervous systems, muscles, or guts, originated depends on a well-supported hypothesis about the phylogenetic relationships among major animal lineages. Traditionally, sponges (Porifera) have been interpreted as the sister group to the remaining animals, a hypothesis consistent with the conventional view that the last common animal ancestor was relatively simple and more complex body plans arose later in evolution. However, this premise has recently been challenged by analyses of the genomes of comb jellies (Ctenophora), which, instead, found ctenophores as the sister group to the remaining animals (the "Ctenophora-sister" hypothesis). Because ctenophores are morphologically complex predators with true epithelia, nervous systems, muscles, and guts, this scenario implies these traits were either present in the last common ancestor of all animals and were lost secondarily in sponges and placozoans (Trichoplax) or, alternatively, evolved convergently in comb jellies. Here, we analyze representative datasets from recent studies supporting Ctenophora-sister, including genome-scale alignments of concatenated protein sequences, as well as a genomic gene content dataset. We found no support for Ctenophora-sister and conclude it is an artifact resulting from inadequate methodology, especially the use of simplistic evolutionary models and inappropriate choice of species to root the metazoan tree. Our results reinforce a traditional scenario for the evolution of complexity in animals, and indicate that inferences about the evolution of Metazoa based on the Ctenophora-sister hypothesis are not supported by the currently available data.