Molecular Systematics of Galeomorph Sharks

[707145]奈勒Galeomorph鲨是现存鲨鱼中分类学上最多样化和最占优势的一类，包括许多大型和著名的物种，如大白鲨、虎鲨、双髻鲨和鲸鲨。巨形兽的化石记录可以追溯到侏罗纪，这表明鲨鱼代表了脊椎动物谱系树的一个早期分支。在这项研究中，爱荷华州立大学的Gavin Naylor将使用从线粒体和核基因组中获得的DNA序列来研究100多种鲨鱼的系统发育关系，包括7种不同目的代表。Naylor将测试四目galeomorph鲨鱼是否都来自一个共同的祖先，并且还将研究每个galeomorph目中几个谱系中的物种之间的关系。系统发育假说将(i)与丰富的galeomorph化石记录结合使用，以评估鲨鱼独特的许多形态适应的时间或起源，以及（ii）作为解释丰富的现有鲨鱼寄生虫多样性数据库的框架。Naylor还将研究DNA序列形成不同基因的程度，以及来自同一基因不同区域的DNA在同一家谱树上收敛的程度。这一分析将提供DNA如何随时间变化的信息，以及如何从DNA序列数据中改进家谱树的估计。

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.