Pomona College, R.C. Seaver Biology Building, Claremont, CA 91711, USA.
Mol Phylogenet Evol. 2013 Apr;67(1):60-71. doi: 10.1016/j.ympev.2012.12.016. Epub 2012 Dec 29.
The model organism Hydra belongs to the hydrozoan clade Aplanulata. Despite being a popular model system for development, little is known about the phylogenetic placement of this taxon or the relationships of its closest relatives. Previous studies have been conflicting regarding sister group relationships and have been unable to resolve deep nodes within the clade. In addition, there are several putative Aplanulata taxa that have never been sampled for molecular data or analyzed using multiple markers. Here, we combine the fast-evolving cytochrome oxidase 1 (CO1) mitochondrial marker with mitochondrial 16S, nuclear small ribosomal subunit (18S, SSU) and large ribosomal subunit (28S, LSU) sequences to examine relationships within the clade Aplanulata. We further discuss the relative contribution of four different molecular markers to resolving phylogenetic relationships within Aplanulata. Lastly, we report morphological synapomorphies for some of the major Aplanulata genera and families, and suggest new taxonomic classifications for two species of Aplanulata, Fukaurahydra anthoformis and Corymorpha intermedia, based on a preponderance of molecular and morphological data that justify the designation of these species to different genera.
模式生物水螅属于水螅纲的无腔动物分支。尽管它是一个广受欢迎的发育模型系统，但对于该分类群的系统发育位置或其最亲近的亲属关系知之甚少。以前的研究对于姐妹群关系存在冲突，并且无法解决该分支内的深节点。此外，还有几个假定的无腔动物分类群从未进行过分子数据采样或使用多个标记进行分析。在这里，我们将快速进化的细胞色素氧化酶 1（CO1）线粒体标记与线粒体 16S、核小核糖体亚基（18S、SSU）和大亚基（28S、LSU）序列相结合，以检查无腔动物分支内的关系。我们进一步讨论了四个不同分子标记在解决无腔动物内系统发育关系中的相对贡献。最后，我们报告了一些主要的无腔动物属和科的形态学共衍征，并根据大量的分子和形态学数据，建议对两种无腔动物物种——Fukaurahydra anthoformis 和 Corymorpha intermedia 进行新的分类分类，这些数据证明将这些物种指定到不同的属是合理的。
