Stach Thomas, Turbeville J M
Department of Biological Sciences, University of Arkansas, 019 West Avenue Annex, Fayetteville 72701, USA.
Mol Phylogenet Evol. 2002 Dec;25(3):408-28. doi: 10.1016/s1055-7903(02)00305-6.
The phylogeny of the Tunicata was reconstructed using molecular and morphological characters. Mitochondrial cytochrome oxidase I (cox1) and 18S rDNA sequences were obtained for 14 and 4 tunicate species, respectively. 18S rDNA sequences were aligned with gene sequences obtained from GenBank of 57 tunicates, a cephalochordate, and a selachian craniate. Cox1 sequences were aligned with the sequence of two ascidians and a cephalochordate obtained from GenBank. Traditional, morphological, life history, and biochemical characters of larval and adult stages were compiled from the literature and analyzed cladistically. Separate and simultaneous parsimony analyses of molecular and morphological data were carried out. Aplousobranch ascidians from three different families were included in a molecular phylogenetic analysis for the first time. Analysis of the morphological, life history, and biochemical characters results in a highly unresolved tree. Aplousobranchiata form a strongly supported monophylum in the analysis of the 18S rDNA data, the morphological data, and the combined data set. Cionidae is not included in the Aplousobranchiata but nests within the Phlebobranchiata. Appendicularia (=Larvacea) nest within the 'Ascidiacea' as the sister taxon of Aplousobranchiata in the parsimony analysis of the 18S rDNA data and the combined analysis. A potential morphological synapomorphy of Aplousobranchiata plus Appendicularia is the horizontal orientation of the larval tail. In the 18S rDNA and the combined analysis, Thaliacea is included in the 'Ascidiacea' as the sister group to Phlebobranchiata. Pyrosomatida is found to be the sister taxon to the Salpidae in analyses of 18S rDNA and combined data, whereas the analysis of the morphological data recovers a sister group relationship between Doliolidae and Salpidae. Results of cox1 analyses are incongruent with both the 18S rDNA and the morphological phylogenies. Cox1 sequences may evolve too rapidly to resolve relationships of higher tunicate taxa. However, the cox1 data may be useful at lower taxonomic levels.
利用分子和形态学特征重建了被囊动物的系统发育。分别获得了14种和4种被囊动物的线粒体细胞色素氧化酶I（cox1）和18S rDNA序列。将18S rDNA序列与从GenBank获得的57种被囊动物、一种头索动物和一种板鳃亚纲脊椎动物的基因序列进行比对。将cox1序列与从GenBank获得的两种海鞘和一种头索动物的序列进行比对。从文献中收集幼虫和成虫阶段的传统、形态、生活史和生化特征，并进行分支分析。对分子和形态数据进行了单独和同时的简约分析。首次将来自三个不同科的单鳃类海鞘纳入分子系统发育分析。对形态、生活史和生化特征的分析产生了一棵高度不确定的树。在对18S rDNA数据、形态数据和组合数据集的分析中，单鳃类形成了一个得到有力支持的单系类群。菊海鞘科不包含在单鳃类中，而是嵌套在鳃海鞘科内。在对18S rDNA数据的简约分析和组合分析中，尾海鞘纲（=幼形纲）嵌套在“海鞘纲”内，作为单鳃类的姐妹分类单元。单鳃类加尾海鞘纲的一个潜在形态共衍征是幼虫尾部的水平方向。在18S rDNA和组合分析中，海樽纲作为鳃海鞘科的姐妹群包含在“海鞘纲”中。在对18S rDNA和组合数据的分析中，火体虫目被发现是磷海鞘科的姐妹分类单元，而对形态数据的分析恢复了住囊虫科和磷海鞘科之间的姐妹群关系。cox1分析的结果与18S rDNA和形态系统发育均不一致。cox1序列可能进化得太快，无法解析较高等被囊动物类群的关系。然而，cox1数据在较低的分类水平上可能有用。
