Collaborative Research: Systematics and Adaptation of the Thaliacea (Tunicata): A Genetic and Morphological Study

海带纲是被囊纲的一个纲，由三组远洋被囊纲组成，分别是火尾纲、水尾纲和刺尾纲。它们都是自由游动的全浮游生物，具有复杂的生命史和在浮游生物中滤食性食草动物的惊人能力。这三目分布在世界各地，但已描述的物种总数不到100种。在某些情况下，表型变异性混淆了之前对系统分类的努力，并在许多看似世界性的形式中留下了隐藏物种的可能性。现有的分类和系统发生都是基于有限数量的形态特征，这不足以解决属和种水平上的关系问题。初步的遗传证据表明，海樽纲属于单系目，而海鞘、水母和火小体则是受到良好约束的单系目。然而，序数以下的关系尚不清楚，经典树和分子树之间已经出现了一些冲突。尽管它们分布在全球，而且具有明显的生态意义，但今天很少有科学家研究海樽纲生物学的任何方面。这在一定程度上可能是由于非专业人员在识别物种方面存在困难，特别是标本在收集过程中经常遭到破坏。这个项目汇集了两名分子动物学家和一名塔利亚纲生态学和生活史专家。研究小组将根据尽可能多的已描述物种的数据，可能至少70%的数据，寻求形态和遗传数据的调和，以发展出一个海樽菊的系统发育。因为这些群体相当小，这是一个可行的目标，不仅可以实现一个得到充分支持的共识系统发育和分类，而且还可以对类进行专题处理，这将对非专家的物种识别有用。拟议研究的更广泛影响包括对全球海洋浮游动物普查的贡献，以及为生物海洋学家提供一个实用的海樽科植物鉴定指南。该项目将支持WHOI的一名博士后研究员，并涉及康涅狄格大学的本科生。项目目标和结果将通过WHOI或康涅狄格大学托管的一个或多个网站广泛公布。

The Thaliacea is a class of Tunicata comprising three groups of pelagic tunicates, the Pyrosomida, Doliolida and Salpida. All are free-swimming holoplanktonic organisms with complex life histories and prodigious capabilities as filter-feeding herbivores in the plankton. These three orders have worldwide distributions yet together number fewer than 100 described species. In some cases phenotypic variability has confused prior efforts at systematic classification and left open the possibility of cryptic species among many seemingly cosmopolitan forms. Existing classifications and phylogenies are all based on a limited number of morphological characters, which have been inadequate to resolve many questions about relationships at the genus and species level. Preliminary genetic evidence suggests that the Thaliacea are monophyletic within the Tunicata andthat salps, doliolids and pyrosomes are well-constrained monophyletic orders. However relationships below the ordinal are unclear, with some conflicts already arising between classical and molecular trees. Despite their global distribution and apparent ecological significance there arefew scientists today working on any aspect of Thaliacean biology. Partly this may be due to the difficulty for non-specialists in identifying species, particularly as specimens are often damaged in collection. This project brings together two molecular zoologists and one expert in Thaliacean ecology and life history. The research team will seek to reconcile morphological and genetic data to develop a phylogeny for the Thaliacea, based on data from as many of the described species as can be obtained, probably at least 70%. Because these groups are fairly small, this is a feasible goal, and will enable not only a well-supported consensus phylogeny and classification, but also a monographic treatment of the Class that will be useful for species identification by nonexperts. Broader impacts of the proposed research include the contribution of results to the global Census of Marine Zooplankton and the provision of a practical identification guide to Thaliacea for biological oceanographers. The project will support a postdoctoral investigator at WHOI and involve undergraduate students at the University of Connecticut. Project objectives and results will be made widely available via one or more websites hosted at WHOI or the University of Connecticut.