Mitochondrial genome and nuclear sequence data support Myzostomida as part of the annelid radiation
Mitochondrial genome and nuclear sequence data support Myzostomida as part of the annelid radiation
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DOI：
10.1093/molbev/msm086
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发表时间：
2007-08-01
影响因子：
10.7
通讯作者：
Tiedemann, Ralph
中科院分区：
文献类型：
--
作者：
Bleidorn, Christoph;Eeckhaut, Igor;Tiedemann, Ralph
棘皮共生体Myzostomida是一种海生蠕虫，显示出神秘的斜生动物的身体平面。在历史上，由于对哪些形态特征在进化上是保守的存在分歧，它们的系统发育起源是模糊的，但现在大多数形态证据指向环节动物的起源。相比之下，最近使用不同分子标记进行的系统发育分析得出了关于分生口虫位置的不同结果，但都表明这些蠕虫不是起源于环节动物。为了重新审视这个问题，我们分析了核基因(18S rDNA、28S rDNA、肌球蛋白II和延伸因子-1α)和几乎完整的肌口类线粒体基因组的数据。在这里，我们表明，分子数据与形态证据相一致，即肌口类是环节动物辐射的一部分。这一结果得到了线粒体(基因序列和序列数据)和核数据以及最近的超微结构研究的有力支持。使用贝叶斯因子比较，替代假设显示缺乏支持。因此，肌口类可能是从一个分段的祖先进化而来的，并在作为棘皮动物共生体的漫长进化历史中获得了派生的解剖学。
The echinoderm symbionts Myzostomida are marine worms that show an enigmatic lophotrochozoan body plan. Historically, their phylogenetic origins were obscured due to disagreement about which morphological features are evolutionarily conserved, but now most morphological evidence points to annelid origins. In contrast, recent phylogenetic analyses using different molecular markers produced variable results regarding the position of myzostomids, but all suggested these worms are not derived annelids. To reexamine this issue, we analyzed data from nuclear genes (18S rDNA, 28S rDNA, Myosin II, and Elongation Factor-1 alpha), and a nearly complete myzostomid mitochondrial genome. Here, we show that the molecular data are in agreement with the morphological evidence that myzostomids are part of the annelid radiation. This result is robustly supported by mitochondrial (gene order and sequence data) and nuclear data, as well as by recent ultrastructural investigations. Using Bayes factor comparison, alternative hypotheses are shown to lack support. Thus, myzostomids probably evolved from a segmented ancestor and gained a derived anatomy during their long evolutionary history as echinoderm symbionts.