Dissertation Research: Phylogeography of Salamanders of the Plethodon Jordani Complex in the Southern Appalachian Mountains

根据蛋白质变异的调查，乔达尼原齿龙复合体是由7种高海拔山地物种组成的集合，它们的形态分化很小，但含有高度的遗传分化。据预测，在最近的冰河时期，温度变化的周期导致了多次的种群隔离和接触，因为火蜥蜴正在跟踪它们有利的环境。这些截然不同的事件可能导致了隔离时的遗传分化和接触时的遗传混合。在许多情况下，这些力量的相互作用如何影响这种物种复合体中的物种形成尚不清楚。这项研究的目的是利用线粒体DNA序列和现有的蛋白质变异数据，通过系统发育分析来检验Jordani复合体中碎片化种群之间的遗传分化和杂交形成的假说。项目意义很少有系统地理学研究有足够的样本在精细的地理尺度上检测自然种群之间的遗传碎片化和二次接触的模式。这项研究试图为蛋白质变异产生的物种假说提供一个详细和精细的系统地理测试。Plethodon jordani复合体的分布相对有限，允许在其分布范围内进行广泛采样，因此，几乎完全描述了线粒体基因的遗传多样性。大样本量和线粒体DNA序列使我们能够区分种群之间正在进行的动态基因交换和历史上不连续的基因交换模式。此外，对蛋白质变异的广泛调查的存在为检查用于量化种群间进化差异和物种形成的组合数据来源提供了理想的情况。

Project DescriptionThe Plethodon jordani complex is an assemblage of seven high-elevation mountain species that show little morphological differentiation, but contain high levels of genetic differentiation according to surveys of protein variation. Cycles of temperature change during the most recent ice ages are predicted to have caused repeated episodes of population isolation and contact as salamanders tracked their favorable environments. These contrasting episodes may have caused genetic ivergence when isolated and genetic mixing while in contact. In many cases it is unclear how the interplay of these forces has affected species formation in this species complex. Objectives of this research are to utilize mitochondrial DNA sequences in tandem with the existing protein variation data to test hypotheses of genetic differentiation and hybrid formation among fragmented populations in the P. jordani complex through phylogenetic analyses.Project Significance Few phylogeographic studies have sufficient sampling to detect on a fine geographic scale the patterns of genetic fragmentation and secondary contact among natural populations. This study seeks to provide a detailed and fine-scale phylogeographic test of species hypotheses that were generated from protein variation. The relatively limited distribution of the Plethodon jordani complex allows extensive sampling across its distribution and, therefore, near complete characterization of genetic diversity for a mitochondrial gene. The large sample sizes and mitochondrial DNA sequences allow us to distinguish ongoing dynamic gene exchange among populations versus historically discontinuous patterns of gene exchange. Furthermore, the existence of extensive surveys of protein variation provides an ideal situation for examining combined data sources for quantifying evolutionary divergence among populations and species formation.