DISSERTATION RESEARCH: Hybridization and polyploidy as drivers of species diversification and niche evolution during rapid radiations

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The South American Andes are among the most species-rich and imperiled hotspots of biodiversity on Earth. Conservation of this region is especially important given its high level of species endemism; of the 45,000 species of plants native to the tropical Andes, nearly half are found nowhere else in the world. In order to effectively conserve this diversity, it is critical to understand the relationships among species as well as how those species form with respect to time and space. However, such an understanding is lacking for many plant groups in this region. This research aims to improve our understanding of diversity in the genus Phlegmariurus, a widespread group of ancient land plants that are represented by approximately 100 species in the high mountains of the Andes, by identifying how hybridization and genome doubling led to the formation of new species in the group. This research provides funding for the researchers to collect these plants in forests and alpine grasslands in Colombia and Ecuador and to use newly developed DNA sequencing technologies to resolve the evolutionary history of this ancient and ecologically prominent group of plants. Further, this funding will allow the researchers to disseminate their results through national and international meetings and peer-reviewed scientific publications, and to train undergraduate students in cutting-edge molecular biology techniques.Species relationships and the evolutionary signature of hybridization in tropical American Phlegmariurus will be inferred using an approach that combines DNA sequencing and genome size estimation via flow cytometry. To supplement materials previously collected in Central America, the researchers will collect leaf material from plants in the Andes of Colombia and Ecuador. Dried leaf material will be used both to extract DNA for sequencing and to infer genome size using flow cytometry. Four nuclear-encoded genes, which can be used to infer if a species is of hybrid origin, will be sequenced using the recently developed sequencing approach on the Pacific Biosciences next-generation DNA sequencing platform. By combining this approach with genome size estimation via flow cytometry, the researchers will be able to identify the number of species in the group that originated from inter-species hybridization and subsequent genome doubling (polyploidization). Using computational phylogenetic methods, the researchers will infer the age of lineages in the genus, the evolutionary relationships among species in the group, and the impact of hybridization on rates of species diversification. These results will not only provide insight into the evolutionary relationships among American species of Phlegmariurus, but improve our understanding of the mechanisms underlying the formation and maintenance of species diversity in the Andean conservation hotspot.