Medusozoan phylogeny and character evolution clarified by new large and small subunit rDNA data and an assessment of the utility of phylogenetic mixture models
Medusozoan phylogeny and character evolution clarified by new large and small subunit rDNA data and an assessment of the utility of phylogenetic mixture models
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DOI：
10.1080/10635150500433615
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发表时间：
2006-02-01
影响因子：
6.5
通讯作者：
Schierwater, B
中科院分区：
文献类型：
--
作者：
Collins, AG;Schuchert, P;Schierwater, B
从31种不同的水母动物中取样的核糖体大亚基（LSU或28S）的近完整序列的新汇编数据集极大地阐明了刺胞动物的系统发育历史。这些数据有很大的力量来辨别许多从以前的工作中得出的相互竞争的关系假设。此外，LSU数据在基于其他分子标记的模棱两可的关键节点上提供了强有力的支持。将LSU序列与核糖体小亚基（SSU或18S）的序列相结合，我们提出了一个关于水母动物关系的详细工作假设，并讨论了这个多样化进化分支的特征进化。Stauromedusae，包括底栖动物，所谓的有柄水母，似乎是所有其他水母动物的姐妹群，这意味着自由游动的水母阶段，运动神经网络和外胚层起源的静泡都是水母动物的特征。自其生命周期被阐明以来，一直没有确定的系统发育亲缘关系的长臂猿，与棘足动物类群冠状动物、根状动物和Semaeostomeae组成了一个分支——acrasped。长方体动物和水螅动物的息肉似乎都是次要简化的。水螅虫是由两个支持良好的分支组成，水螅虫和水螅虫。水水母在水螅纲内的位置表明其祖先水螅类动物具有双相生命周期，水母是通过内密码子形成的。因此，最近假设的内密码子和双边中胚层之间的同源性是值得怀疑的。Laingiomedusae，通常被认为是尾线组Narcomedusae的亲密盟友，相反，被证明是Hydroidolina的一个成员。水螅物种复合体的重要模式生物是一个分支的一部分，无尾虫，与其他水螅动物直接发展，不涉及纤毛水螅阶段。最后，将系统发育混合模型应用于我们的数据被证明与更传统的系统发育方法（包括明确的假设检验和多重最优性标准下的自举分析）相比几乎没有附加价值。
A newly compiled data set of nearly complete sequences of the large subunit of the nuclear ribosome (LSU or 28S) sampled from 31 diverse medusozoans greatly clarifies the phylogenetic history of Cnidaria. These data have substantial power to discern among many of the competing hypotheses of relationship derived from prior work. Moreover, LSU data provide strong support at key nodes that were equivocal based on other molecular markers. Combining LSU sequences with those of the small subunit of the nuclear ribosome (SSU or 18S), we present a detailed working hypothesis of medusozoan relationships and discuss character evolution within this diverse clade. Stauromedusae, comprising the benthic, so-called stalked jellyfish, appears to be the sister group of all other medusozoans, implying that the free-swimming medusa stage, the motor nerve net, and statocysts of ecto-endodermal origin are features derived within Medusozoa. Cubozoans, which have had uncertain phylogenetic affinities since the elucidation of their life cycles, form a clade-named Acraspeda-with the scyphozoan groups Coronatae, Rhizostomeae, and Semaeostomeae. The polyps of both cubozoans and hydrozoans appear to be secondarily simplified. Hydrozoa is comprised by two well-supported clades, Trachylina and Hydroidolina. The position of Limnomedusae within Trachylina indicates that the ancestral hydrozoan had a biphasic life cycle and that the medusa was formed via an entocodon. Recently hypothesized homologies between the entocodon and bilaterian mesoderm are therefore suspect. Laingiomedusae, which has often been viewed as a close ally of the trachyline group Narcomedusae, is instead shown to be unambiguously a member of Hydroidolina. The important model organisms of the Hydra species complex are part of a clade, Aplanulata, with other hydrozoans possessing direct development not involving a ciliated planula stage. Finally, applying phylogenetic mixture models to our data proved to be of little additional value over a more traditional phylogenetic approach involving explicit hypothesis testing and bootstrap analyses under multiple optimality criteria.