Dissertation Research: A Phylogenetic Analysis of the Major Lineages of Fishes Utilizing Direct Sequencing of Ribosomal RNA

这项研究将确定主要原始鱼类群体(七鳃鳗、八目鳗、鲨鱼、鳍鱼、肺鱼、腔棘鱼、鲟鱼、白鳍鱼、银鱼和弓鳍)的起源时间和进化相关性，以及特定种类的高级鱼类，其独特的形态和栖息地是相对较新出现的。洞察鱼类群体的进化对于我们理解导致今天高度多样化和复杂的脊椎动物存在的进化机制和适应至关重要。这些鱼类的进化树将建立在比较它们的基因序列的基础上，这些基因序列是从基因产物RNA的序列中推断出来的。一旦根据这些分子数据构建了鱼类进化树，它将与由其他类型的特征构建的树进行比较，例如形态差异，以确定哪种特征组合在解决进化关系方面最有效。一旦建立了最有可能的鱼类进化树，就有可能调查导致今天存在的鱼类物种多样性的进化种类和进化速度。一旦鱼类进化的“历史”被确立，它将为一个物种在面对变化的环境(自然或人类影响)时存在的各种限制和机会提供洞察。

This study will determine the times of origin and evolutionary relatedness of the major groups of primitive fishes (lampreys, hagfishes, sharks, rays, lungfishes, coelacanth, sturgeons, paddlefish, gars, and bowfins as well as selected species of advanced fishes, whose distinctive morphologies and habitats have arisen relatively recently. Insights into the evolution of fish groups whose ancestors gave rise to all land vertebrates is crucial to our understanding of the evolutionary mechanisms and adaptations leading to the highly diversified and complex vertebrates existing today. The evolutionary tree for these fishes will be constructed on the basis of comparing the sequences of their genes inferred from the sequence of a gene product, RNA. Once the evolutionary tree for fishes is constructed from these molecular data, it will be compared with trees constructed form other kinds of traits, for example morphological differences, in order to determine what combination of traits is most effective in resolving evolutionary relationships. Once the most likely evolutionary tree for the fishes is established, it will be possible to investigate the kinds and rates of evolution that have led to the diversity of fish species that exist today. Once the "history" of fish evolution is established, it will provide insight about the kinds of constraints and opportunities that exist for a species when it faces altered environments (natural or human influenced).