Phylogenetic analysis of phenotypic characters and evolutionary transformations in Appendicularia (= Larvacea) and their consequences for the reconstruction of the groundplan of Chordata

脊索动物包括三个单系动物类群：被囊动物（= Tunicata），刺小动物（= cephalalochordata）和脊椎动物（=颅动物）。被囊动物大约有2700种，它们的生命史策略和身体计划的多样性令人眼花缭乱；许多种类的生物作为无底生物附着在基质上，其他种类的生物自由地漂浮在浮游生物中，还有一些在世代之间表现出惊人的多态性。最近的系统发育学和基于形态的系统发育学一致将尾尾鱼（= Larvacea）定位为其余被囊动物的姐妹类群。这使得大约70种尾尾虫处于阐明被囊动物进化的关键位置，因为原始特征可以预期优先发生在尾尾虫身上。现代形态学研究几乎完全局限于一种物种- - - Oikopleura dioica - - -阻碍了对这一重要的动物类群的差异进行可靠的评估。深海脊索属（Bathochordaeus）的成员甚至没有现代的显微镜研究。最近的系统发育分析只包括一个尾尾虫物种，而基于18S rdna序列的较早的分子系统发育包括一个科的三个物种。本项目将对三科13种尾尾虫标本进行详细的形态分析。一个主要目标是基于数字解剖和免疫组织学分析结合共聚焦激光扫描显微镜的分支分析数据矩阵的概念化。只要有可能，这些分析将辅以透射电子显微镜调查。(1)按现代标准对该关键分类单元的形态差异进行采样和记录。(2)提出最大字符数的初级同源假设。(3)首次提出了基于透明枝系分析的形态学系统发育假说。(4)基于超微结构分析，可以提出器官系统功能形态的假设。(5)所有器官系统的进化转变都将得到可复制的解释。(6)对尾虫最后共同祖先的地面格局进行了枝状重建。(7)根据这些分支分析，讨论了高等分类群Tunicata、olfactes （= Tunicata + Craniota）和Chordata的进化情景。

Chordata comprises three monophyletic animal taxa: tunicates (= Tunicata), lancelets (= Cephalochordata), and vertebrates (= Craniota). With approximately 2700 species, tunicates show a bewildering diversity of life-history strategies and body plans; many species live attached to the substrate as sessile organisms, others float freely in the plankton, and some display spectacular polymorphisms between generations. Recent phylogenomic and morphology-based phylogenies concur in positioning Appendicularia (= Larvacea) as sister group to the remaining tunicates. This puts Appendicularia with approximately 70 species in a key position to elucidate tunicate evolution, because primitive traits can be expected to occur preferentially in appendicularians. Modern morphological studies are almost exclusively restricted to one species – Oikopleura dioica – impeding a reliable assessment of the disparity within this phylogenetically important group of animals. For the members within the deep-sea genus Bathochordaeus not even light microscopical modern investigations exist. The recent phylogenomic analyses comprise but a single appendicularian species, older molecular phylogenies based on 18S rDNA-sequences included up to three species of a single family. In the proposed project specimens of 13 appendicularian species of all three families will be morphologically analyzed in detail. A major goal is the conceptualization of a data matrix for cladistic analysis based on digital anatomies and immunohistological analyses combined with confocal laser scanning microscopy. Wherever possible, these analyses will be complemented by transmission electron microscopic investigation. In this way, the following goals will be achieved:(1) The morphological disparity of this key taxon will be sampled and documented according to modern standards.(2) Primary homology hypotheses of a maximum number of characters will be formulated.(3) For the first time, a morphology based phylogenetic hypothesis based on a transparent cladistic analysis will be suggested.(4) Hypotheses of the functional morphology of organ systems can be proposed based on the ultrastructural analyses.(5) Evolutionary transformations will be reproducibly explained in all organ systems.(6) A cladistic reconstruction of the ground pattern in the last common ancestor of Appendicularia will be achieved.(7) Implications for evolutionary scenarios of higher taxa Tunicata, Olfactores (= Tunicata + Craniota), and Chordata grounded in these cladistic analyses will be discussed.