Illuminating the Base of the Annelid Tree Using Transcriptomics
Illuminating the Base of the Annelid Tree Using Transcriptomics
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DOI：
10.1093/molbev/msu080
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发表时间：
2014-06-01
影响因子：
10.7
通讯作者：
Struck, Torsten H.
中科院分区：
文献类型：
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作者：
Weigert, Anne;Helm, Conrad;Struck, Torsten H.
Annelida是拥有分段的三个动物群体之一，在考虑不同性格特征的进化时发挥着核心作用。甚至有人提出，这种双边生物的祖先类似于环节动物。然而，关于环节动物的系统发育，特别是在基本关系方面，一直缺乏有力的系统发育。我们的研究基于包含68,750-170,497个氨基酸残基的转录数据，从305到622个蛋白质，解决了环节动物的关系，包括毛翅科，两性科，星虫，Oweniidae和Magelonidae在树的底部。在大多数分析中，已经表明也属于基辐射的肌口纲在环节动物中被深嵌套，作为Errantia的姊妹群。在我们重建了环节动物系统发育的基础上，我们发现基本的分枝分类群包括各种各样的生活方式，如管状栖息和沉积物取食，内底栖动物和穴居动物，管状动物和滤食性动物，以及迷途和食肉形式。祖先特征状态重建表明，祖先环节动物有一对感觉或凹槽触须，双细胞眼睛，两叉状附足，有简单的触角，缺乏颈部器官。由于最古老的Annelida化石被报道为Sipuncula(520 Ma)，我们推测早期环节动物的多样化至少发生在下寒武世。
Annelida is one of three animal groups possessing segmentation and is central in considerations about the evolution of different character traits. It has even been proposed that the bilaterian ancestor resembled an annelid. However, a robust phylogeny of Annelida, especially with respect to the basal relationships, has been lacking. Our study based on transcriptomic data comprising 68,750-170,497 amino acid sites from 305 to 622 proteins resolves annelid relationships, including Chaetopteridae, Amphinomidae, Sipuncula, Oweniidae, and Magelonidae in the basal part of the tree. Myzostomida, which have been indicated to belong to the basal radiation as well, are now found deeply nested within Annelida as sister group to Errantia in most analyses. On the basis of our reconstruction of a robust annelid phylogeny, we show that the basal branching taxa include a huge variety of life styles such as tube dwelling and deposit feeding, endobenthic and burrowing, tubicolous and filter feeding, and errant and carnivorous forms. Ancestral character state reconstruction suggests that the ancestral annelid possessed a pair of either sensory or grooved palps, bicellular eyes, biramous parapodia bearing simple chaeta, and lacked nuchal organs. Because the oldest fossil of Annelida is reported for Sipuncula (520 Ma), we infer that the early diversification of annelids took place at least in the Lower Cambrian.