A comprehensive molecular phylogeny of spoon worms (Echiura, Annelida): Implications for morphological evolution, the origin of dwarf males, and habitat shifts.
A comprehensive molecular phylogeny of spoon worms (Echiura, Annelida): Implications for morphological evolution, the origin of dwarf males, and habitat shifts.
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DOI：
10.1016/j.ympev.2016.03.003
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发表时间：
2016-06
影响因子：
4.1
通讯作者：
R. Goto
中科院分区：
文献类型：
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作者：
R. Goto
棘尾动物（匙形蠕虫）是衍生环节动物，有继发性失去分割。最近，两个分子系统学研究进行了解决科间关系的echiurans。然而，树的拓扑结构是不一致的，在这两项研究中的分类单元抽样是有限的。因此，Echiurans的系统发育关系仍然存在争议。在这项研究中，我重新评估echiurans的分子遗传学，使用三个核（18 S，28 S，和H3）和两个线粒体（16 S和COI）基因的49个echiurans物种，属于17-19属，5科。结果表明，Echiurans形成以下两个主要分支：一个性别单态组（Echiuridae，Urechidae和Thalassematidae）和一个性别二态组（Bonelliidae和Ikedidae）。支持刺尾科与Echiuridae、池尾科与Bonelliidae的姐妹群关系。该分析还支持以下的属之间的关系在Thalassematidae：{Arhynchite[（Thalassema，Lissomyema）（Ochetostoma，Listriolobus，Ikedosoma，Anelorphynchus）]}.此外，我评估了重要的分类特征（体壁纵向肌肉组织，长鼻的形状，生殖器唇的形状，和身体的颜色）和栖息地的变化（水深和基板类型）的进化模式，使用祖先的状态重建分析。分析表明，性二型的Echiurans起源于浅水沃茨，其次入侵深海，虽然深到浅的栖息地逆转也被检测到。与先前的假设相反，echiurans中矮小雄性的两性异形可能是对深海环境的预适应。提出了一个新的棘尾类分类，其中棘尾类包括两个总科，即Echiuroidea（包括Echiuridae、Urechidae和Thalassematidae）和Bonellioidea（包括Bonelliidae和Ikedidae）。
Echiurans (spoon worms) are derived annelids that have secondarily lost segmentation. Recently, two molecular phylogenetic studies were performed to resolve the interfamily relationship of echiurans. However, the tree topologies were incongruent and taxon sampling was limited in both the studies. Thus, the phylogenetic relationships within echiurans remain contentious. In this study, I reevaluated the molecular phylogeny of echiurans, using three nuclear (18S, 28S, and H3) and two mitochondrial (16S and COI) genes of 49 echiuran species belonging to 17–19 genera and five families. Results showed that echiurans form the following two major clades: a sexually monomorphic group (Echiuridae, Urechidae, and Thalassematidae) and a sexually dimorphic group (Bonelliidae and Ikedidae). The sister group relationships between Urechidae and Echiuridae, as well as between Ikedidae and Bonelliidae, were supported. The analysis also supported the following relationships among genera within Thalassematidae: {Arhynchite[(Thalassema,Lissomyema) (Ochetostoma,Listriolobus,Ikedosoma,Anelassorhynchus)]}. Furthermore, I evaluated the evolutionary patterns of important taxonomic characteristics (body-wall longitudinal musculature, proboscis shape, gonostmal lip shape, and body color) and habitat shifts (water depth and substrate type), using ancestral state reconstruction analyses. The analyses showed that sexually dimorphic echiurans originated in the shallow waters and secondarily invaded the deep sea, although deep-to-shallow habitat reversal was also detected. In contrary to the previous hypothesis, sexual dimorphism with dwarf males in echiurans may have been a preadaptation to the deep-sea environment. The analyses also showed that habitat shifts from soft sediments to hard substrates occurred in Thalassematidae and Bonelliidae, respectively.A new classification of echiurans, in which Echiura comprises two superfamilies, namely Echiuroidea (with Echiuridae, Urechidae, and Thalassematidae) and Bonellioidea (with Bonelliidae and Ikedidae), is proposed.