AnnEvol - Evolution and phylogeny of Annelida based on phylogenomic data (i.e. EST libraries)

环节动物是一种古老且非常多样化的动物分类群，栖息在从深海到陆地土壤的各种生境中。作为具有节段性的三个动物类群之一，破译环节动物的进化对于我们理解节段性的进化至关重要。传统上，环节动物由多毛类(如蚯蚓)和阴蒂动物(如蚯蚓和水蚤)组成。虽然Clitellata在多毛类中的位置得到了很好的支持，但它们的多毛类姐妹群是不确定的。已证明未分段的动物门Sipuncula和Echiura以及Myzostomida是环节动物辐射的一部分，但除Echiura外，它们的姐妹分类群仍未确定。虽然已经提出了更具包容性的分类单位(鞘翅目、帕尔帕塔目、卡纳利帕塔目和针叶目)，但利用形态或分子的单基因或多基因数据很难解决环节动物的关系。因此，环节动物的系统发育仍然没有解决，任何关于环节动物进化的结论都是有争议的，比如祖先环节动物的形式是穴居的还是爬行的。这使人们对使用样本物种作为祖先环节动物疾病的代表提出了质疑(例如，扁豆)。另一方面，两位申请人收集的初步数据表明，使用表达序列taqs(=EST)文库大幅增加每个分类单元的分子数据量会导致节点支持和分析之间的一致性增加。因此，在这个拟议的项目中，我们希望使用基于EST文库的系统发育学方法来解决环节动物的系统发育问题。几种环节动物的EST文库应使用454测序生成。与特定基因的扩增相比，这使每个分类单元的序列信息量增加了三到四个数量级。鉴于我们的分类单元样本，我们期望有力地解析环节动物生命树的脊梁，从而有助于得出关于环节动物进化的结论。

Annelida is an ancient and very diverse animal taxon inhabiting diverse habitats from the deep sea to terrestrial soils. Being one of the three animal groups with segmentation, deciphering the evolution of Annelida is crucial to our understanding of the evolution of segmentation. Traditionally, Annelida comprised polychaetes (e.g., lugworms) and clitellates (e.g., earthworms and leeches). While the placement of Clitellata within polychaetes is well supported, their polychaete sistergroup is uncertain. It has been shown that the unsegmented animal “phyla” Sipuncula and Echiura as well as Myzostomida are part of the annelid radiation, but except for Echiura their annelid sistertaxa remain undetermined. Although more inclusive taxonomic units (Scolecida, Palpata, Canalipalpata, and Aciculata) have been put forward, resolving annelid relationships has been difficult using either morphological or molecular single or multiple gene data. Thus, the phylogeny of Annelida is still unresolved and any conclusions about the evolution of Annelida, like the form of the ancestral annelid either as burrowing or as crawling are contentious. This is calling into question the use of exemplar species as representatives of the ancestral annelid condition (e.g., Platynereis). On the other hand, preliminary data gathered by the two applicants show that substantially increasing the amount of molecular data per taxon using expressed sequence taqs (= EST) libraries results in an increase in both nodal support and congruence between analyses. Therefore, in this proposed project we want to resolve the phylogeny of Annelida using a phylogenomic approach based on EST libraries. EST libraries of several annelids shall be generated using 454 sequencing. This increases the amount of sequence information per taxon by three to four orders of a magnitude in comparison to the amplification of specific genes. We expect to robustly resolve the backbone of the annelid tree of life given our taxon sampling and thus to contribute to conclusions regarding the evolution of Annelida.