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

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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.