DISSERTATION RESEARCH: Independent evolution and ancestral conditions in the gnathostome axial column

脊椎的存在，即使只是由软骨构成，也是脊椎动物区别于其无脊椎亲属的特征。尽管它在所有有颌脊椎动物的身体计划中处于中心地位，但引起脊柱的早期进化历史和发育机制尚未得到很好的理解。在不同的脊椎动物群体中，特别是在鱼类中，构成脊椎骨的椎骨在形状、组成和结构上都有很大的不同。此外，鱼类主要类群的早期化石记录表明，许多脊椎的基本组成部分的进化完全独立于其他组成部分。该项目的目标是记录脊椎发育在缺乏研究的群体，如鲨鱼和冰鞋，以确定有多少独立的进化实际上发生在脊椎的深层历史，并提供必要的比较与目前的理解脊椎发育在硬骨鱼。该项目结合祖先的国家重建nathostome超树与计算机断层扫描，基因表达，和命运作图实验来研究鱼类脊椎动物进化和发育的宏观进化模式。软骨鱼类是拟议研究的主要焦点，因为它们占据了一个关键的系统发育位置，作为硬骨鱼类最接近的外类群。软骨鱼类在发育和功能研究中通常被认为是祖先脊椎动物的典范，但它们的大部分形态的原始或衍生状态尚不清楚，并且重新引起了研究兴趣。确定祖先的条件和同源性的轴柱复杂的知情评估的研究和数据从替代脊椎动物模型系统是必不可少的。此外，鲨鱼和化石一样，都是吸引公众兴趣的有魅力的研究对象。为了帮助向公众传达这个项目和其他相关项目的性质，研究人员将使用计算机断层扫描（静态和动画）和鲨鱼化石标本来教育当地学校的学生进化生物学的重要性和相关性。

The presence of a backbone, even if only made of cartilage, is the feature that distinguishes vertebrate animals from their invertebrate relatives. Despite its central position in the body plans of all jawed vertebrates, the early evolutionary history and developmental mechanisms that gave rise to the vertebral column are not well understood. Across different vertebrate groups, and among fishes in particular, the vertebrae that make up the backbone are remarkably varied in their shape, composition, and structure. Furthermore, the early fossil record of the major groups of fishes shows that many evolved fundamental components of the vertebral column quite independently of others. The goals of this project are to document vertebral development in poorly studied groups such as sharks and skates, to determine how much independent evolution actually occurred in the deep history of vertebrae, and to provide essential comparisons with the current understanding of vertebral development in bony fishes.This project combines ancestral state reconstructions on gnathostome supertrees with computed tomography, gene expression, and fate mapping experiments to investigate the macroevolutionary patterns of vertebral evolution and development in fishes. Chondrichthyans are the main focus of the proposed research because they occupy a key phylogenetic position as the most proximate outgroup to the Osteichthyes. Chondrichthyans are often considered exemplars of ancestral vertebrate conditions in developmental and functional studies, but the primitive or derived status of much of their morphology is unclear and the subject of renewed research interest. Identifying ancestral conditions and homoplasy in the axial column complex is essential for the informed evaluation of studies and data obtained from alternative vertebrate model systems. Moreover, sharks as well as fossils are charismatic study subjects that effectively capture public interest. To help communicate the nature of this and other related projects to the public, the investigators will use computed tomographic scans (static and animated), and fossil shark specimens to educate students at local schools about the importance and relevance of evolutionary biology.