Schulze Anja, Cutler Edward B, Giribet Gonzalo
Museum of Comparative Zoology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA.
Mol Phylogenet Evol. 2007 Jan;42(1):171-92. doi: 10.1016/j.ympev.2006.06.012. Epub 2006 Jul 5.
The intra-phyletic relationships of sipunculan worms were analyzed based on DNA sequence data from four gene regions and 58 morphological characters. Initially we analyzed the data under direct optimization using parsimony as optimality criterion. An implied alignment resulting from the direct optimization analysis was subsequently utilized to perform a Bayesian analysis with mixed models for the different data partitions. For this we applied a doublet model for the stem regions of the 18S rRNA. Both analyses support monophyly of Sipuncula and most of the same clades within the phylum. The analyses differ with respect to the relationships among the major groups but whereas the deep nodes in the direct optimization analysis generally show low jackknife support, they are supported by 100% posterior probability in the Bayesian analysis. Direct optimization has been useful for handling sequences of unequal length and generating conservative phylogenetic hypotheses whereas the Bayesian analysis under mixed models provided high resolution in the basal nodes of the tree.
基于来自四个基因区域的DNA序列数据和58个形态特征，对星虫类蠕虫的种内关系进行了分析。最初，我们以简约性作为最优标准，在直接优化下分析数据。随后，利用直接优化分析产生的隐含比对，对不同数据分区采用混合模型进行贝叶斯分析。为此，我们对18S rRNA的茎区应用了双联体模型。两种分析都支持星虫动物门的单系性以及该门内大多数相同的分支。两种分析在主要类群之间的关系上存在差异，但直接优化分析中的深层节点通常显示出较低的自展支持率，而在贝叶斯分析中它们得到了100%的后验概率支持。直接优化对于处理不等长序列和生成保守的系统发育假设很有用，而混合模型下的贝叶斯分析在树的基部节点提供了高分辨率。
