Molecular phylogeny of choanoflagellates, the sister group to Metazoa
Molecular phylogeny of choanoflagellates, the sister group to Metazoa
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DOI：
10.1073/pnas.0801667105
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发表时间：
2008-10-28
影响因子：
11.1
通讯作者：
Baldauf, S. L.
中科院分区：
文献类型：
--
作者：
Carr, M.;Leadbeater, B. S. C.;Baldauf, S. L.
领鞭毛虫是单细胞水生鞭毛虫，具有独特的形态，由一个带有单根鞭毛的细胞组成，鞭毛周围有一圈微绒毛“领”。由于它们与海绵的领细胞（ choanocytes）惊人地相似，长期以来一直引起进化生物学家的兴趣。分子系统发育学已经证实领鞭毛虫和后生动物之间关系密切，而且第一个领鞭毛虫基因组序列最近已经发表。然而，领鞭毛虫内部的分子系统发育研究仍然极其有限。因此，对于领鞭毛虫的进化或者领鞭毛虫和后生动物之间关系的确切性质知之甚少。我们对领鞭毛虫形态多样性的广泛样本（包括目前培养中大多数可用的物种）的四个基因进行了测序。对这些序列单独以及组合进行的系统发育分析否定了该类群的许多传统分类。分子数据也有力地支持领鞭毛虫的单系性，否定了后生动物起源于一个真正的领鞭毛虫祖先的观点。将形态和生态特征的互补矩阵映射到系统发育树上，可以重新解释领鞭毛虫的特征进化，并预测它们最后共同祖先的性质。
Choanoflagellates are single-celled aquatic flagellates with a unique morphology consisting of a cell with a single flagellum surrounded by a "collar" of microvilli. They have long interested evolutionary biologists because of their striking resemblance to the collared cells (choanocytes) of sponges. Molecular phylogeny has confirmed a close relationship between choanoflagellates and Metazoa, and the first choanoflagellate genome sequence has recently been published. However, molecular phylogenetic studies within choanoflagellates are still extremely limited. Thus, little is known about choanoflagellate evolution or the exact nature of the relationship between choanoflagellates and Metazoa. We have sequenced four genes from a broad sampling of the morphological diversity of choanoflagellates including most species currently available in culture. Phylogenetic analyses of these sequences, alone and in combination, reject much of the traditional taxonomy of the group. The molecular data also strongly support choanoflagellate monophyly rejecting proposals that Metazoa were derived from a true choanoflagellate ancestor. Mapping of a complementary matrix of morphological and ecological traits onto the phylogeny allows a reinterpretation of choanoflagellate character evolution and predicts the nature of their last common ancestor.