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A study of plant domestication and evolution through the taxonomic revision of wild North American Humulus, a phytochemical assay for stimulant alkaloids in Celastraceae, and a phylogeographic analysis of Catha edulis in areas of historic cultivation




Tembrock, Luke Raymond, author
Simmons, Mark P., advisor
Angert, Amy L., committee member
Richards, Christopher M., committee member
Ward, Sarah M., committee member

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The cultivation of plant species is essential to the survival of humans. The process of artificial selection that is used to modify wild individuals into improved cultivars results in genetic and morphological changes from wild progenitors. In order to understand the evolutionary patterns and processes involved with artificial selection both wild and cultivated populations must be thoroughly studied. Numerous methods are used to study the process of evolution under cultivation such as biology, chemistry, geography, history, linguistics and archeology. The understanding of evolution in a crop species is essential in current improvement programs to increase yield for a given crop. I employed methods from the fields of taxonomy, analytical chemistry and phylogeography to study the process of evolution in cultivated plant species and/or their wild relatives. From a review of taxonomic, genetic, and phytochemical literature, as well as examination of morphological features I revised the wild North American Humulus (Cannabacae) in a manner that properly delimits the diversity found among the North American species. Using GC–MS and a forensics based derivatization method I assayed for the stimulant alkaloids cathinone, cathine, and similar compounds across the Celastraceae plant family. It was found that that qat (Catha edulis) was the only species of those tested that biosynthesized cathinone and cathine. Using phylogeographic and population genetic techniques I inferred three wild regional origins, hybridization and numerous translocations out of the centers of origin for cultivated qat. From farmer interviews I examined what properties, genotype, phenotype, and/or geography explained the naming convention for qat cultivars among qat farmers. The character of stem color was found to highly plastic and thus genotype was not significantly correlated with the naming convention. Geographic patterns were confirmed for several cultivar names suggesting that anthropogenic factors are important in the naming conventions used among qat farmers. These four separate studies provide findings that not only clarify our understanding of evolutionary patterns among wild and cultivated species but provide a framework for breeding, conservation and forensic applications in the future.


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