Dissertation Research: Host Race Formation and Phylogeography of a Plant Parasite

矮小的槲寄生（Arceuthobium divaricatum）是一种寄生于西南部六种矮松的寄生植物。本项目将研究寄主选择、历史地理隔离和随后的寄主迁移对散斑姬蜂种群间遗传差异模式的影响。本研究的目的是确定这些因素如何共同促进了散斑拟南蝽的进化。叶绿体DNA序列将用于确定寄主选择是否在拟南芥的进化中起作用。此外，将分析序列变异，以确定是否可以检测到由于历史地理隔离造成的种群分化。很少有研究同时考察寄主选择和历史地理隔离对物种内种群分化的影响。通常，进化生物学家将这些因素中的一个或另一个归因于形成这些种群差异的原因。这一研究将加强对不同因素如何影响一个物种进化的理解。此外，由于对寄生植物的种群结构知之甚少，本研究将加强对寄生植物物种迁移、基因流动和种群分化的认识。

The dwarf mistletoe, Arceuthobium divaricatum, is a parasitic plant that parastizes six species of pinon pines in the southwest. This project will examine the effects of host selection, historic geographic isolation and subsequent host migration on the patterns of genetic differences among populations of A. divaricatum. The goal of this study is to determine how these factors together have fostered the evolution of A. divaricatum. Chloroplast DNA sequences will be used to determine if host selection has played a role in the evolution of A. divaricatum. In addition, sequence variation will be analyzed to determine whether population differentiation due to historic geographic isolation can be detected. Few studies have simultaneously examined the influence of host selection and historic geographic isolation on the differentiation of populations within a species. Often, evolutionary biologists credit either one or the other of these factors in shaping these population differences. This study in A. divaricatum will enhance the understanding of how various factors influence the evolution of a species. Additionally, because very little is known about population structures of parasitic plants, this study will enhance the understanding of migration, gene flow and population differentiation in a parasitic plant species.