Dissertation Research: Molecular Systematics of Artemisia Sect. Tridentatae

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9311086 Watson Artemesia ( sensu lato ) L. is composed of approximately 400 species distributed throughout the north temperate regions of the world. It is the largest and ecologically most important genus in the Tribe Anthemideae (Asteraceae). The genus has been the subject of numerous comparative biosystematic investigations, but remains poorly understood. Section Tridentatae is native to western North America and plays an important ecological role in the sagebrush communities. Tridentatae is composed of 11 species of xerophytic shrubs, separated from the other North American species by the presence of homogamous flower heads. The rapid expansion and divergence of Tridentatae , coupled with wind pollination has resulted in extensive convergence and parallel evolution. This has made interpretation of phylogenetic relationships difficult. The main objectives of this study are to elucidate interspecific phylogenetic relationships within Tridentatae , and to determine the affinity of Tridentatae to other subgeneric taxa of Artemesia and to the segregate genus Seriphidium . Several molecular techniques will be utilized including phylogenetic analysis of chloroplast DNA and nuclear ribosomal DNA restriction site maps and analysis of sequence data from the ORFk (Open Reading Frame k) region of the cpDNA genome. Previously proposed hypotheses of evolutionary relationships of Tridentatae will be tested using cladistic analyses of molecular data. An examination of concordance between cytoplasmic and nuclear marker based phylogenies of interspecific relationships will be used to test proposed modes of speciation and to examine patterns of character evolution. The inferred phylogenies will be useful in understanding the evolutionary and ecological success of Tridentatae in the cold deserts of western North America. %%% This project will obtain molecular data (both from the chloroplast and nuclear genomes) for 11 species of sagebrush in the Section Tridentatae of the genus Artemesia . These data will be used to decide relationships among these species that have been the subject of some confusion when morphological characters have been used to establish relationships. These woody shrubs are a highly visible and important component of the cold desert ecosystem and understanding species relationships will enhance other research efforts in ecology and biogeography of these plants. ***