Molecular Systematics of Galeomorph Sharks

小行星9707145 Galeomorph鲨鱼是最具分类多样性和优势的鲨鱼群，包括许多大型和众所周知的物种，如大白色，虎鲨，双髻鲨和鲸鲨。 这些盔形动物有着广泛的化石记录，一直延伸到侏罗纪，这表明鲨鱼是脊椎动物谱系树中的一个早期分支。 在这项研究中，爱荷华州州立大学的加文·内勒将利用从线粒体和核基因组中获得的DNA序列来研究100多种鲨鱼之间的系统发育关系，其中包括7个不同目的代表。 内勒将测试这四个盔形鲨目中的每一个是否都来自一个共同的祖先，并将研究每个盔形鲨目中几个谱系中物种之间的关系。 系统发育假说将被用来（一）与丰富的galeomorph化石记录，以评估时间或鲨鱼独特的许多形态适应的起源，和（二）作为一个框架，解释丰富的，现有的鲨鱼寄生虫多样性数据库。 Naylor还将研究不同基因的DNA序列和同一基因不同区域的DNA序列在同一系谱树上的聚合程度。 这种分析将提供有关DNA如何随时间变化以及如何改进从DNA序列数据估计系谱树的信息。

9707145 Naylor Galeomorph sharks are the most taxonomically-diverse and dominant group of living sharks, and include many of the large and well known species such as the great white, tiger, hammerhead, and whale sharks. The galeomorphs have an extensive fossil record that extends to the Jurassic, demonstrating that sharks represent an early offshoot in the vertebrate genealogical tree. In this research, Gavin Naylor of Iowa State University will employ DNA sequences acquired from both the mitochondrial and nuclear genomes to study phylogenetic relationships among well over 100 species of sharks, including representatives of seven different orders. Naylor will test whether each of the four orders of galeomorph sharks were derived from a common ancestor, and also will examine relationships among species in several lineages within each galeomorph order. The phylogenetic hypothesis will be used (i) in conjunction with the rich galeomorph fossil record to assess the time or origin of many morphological adaptations unique to sharks, and (ii) as a framework for interpreting the rich, existing database on shark parasite diversity. Naylor also will investigate the extent to which DNA sequence form different genes and from different regions of the same gene converge on the same genealogical tree. This analysis will provide information as to how DNA changes over time and how estimation of genealogical trees from DNA sequence data can be improved.