DISSERTATION RESEARCH: Adaptive radiation and hybridization: testing the hybrid swarm origin hypothesis for adaptive radiations in a phylogenetic framework

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Adaptive radiation and ecological opportunity are known to play major roles in the formation of new biodiversity. In this model, a few ancestral species diversify rapidly to fill ecological space with a variety of new morphological and ecological strategies. Recently, hybridization among closely related species has been hypothesized to play an important role during the early stages of an adaptive radiation, but studies investigating this process in plants are currently lacking. This project will evaluate the role of hybridization in facilitating an adaptive radiation using the Andean plant genus Lachemilla (Rosaceae) as a model. Lachemilla comprises approximately 50 described species and is restricted to high elevation habitats throughout the Andes. Phylogenetic analyses of chloroplast and single-copy nuclear DNA gene sequences from multiple Lachemilla species will first be used to reconstruct evolutionary relationships. Using this evolutionary framework, researchers will then use a variety of statistical approaches to investigate the role played by hybridization in driving diversification within the lineage. This research will provide extensive training in systematics and evolutionary biology to a graduate student, and enhance international scientific collaboration with researchers in Ecuador. This project will provide training for one undergraduate student in laboratory techniques and data analysis, and also provide valuable mentoring experience for the co-PI. This project will use phylogenetic methods to investigate and test the hybrid swarm origin and syngameon hypotheses for the generation of functional diversity during an adaptive radiation using the plant genus Lachemilla (Rosaceae). A robust and comprehensive phylogeny from hundreds of Lachemilla accessions using high-throughput sequencing approaches of whole chloroplast and multiple single-copy nuclear regions will be generated using Bayesian approaches. This phylogenetic framework will then be used to first test for evidence of hybridization, and then investigate whether morphological, functional, and phylogenetic diversification in the clade coincides with hybridization events. By integrating modern comparative phylogenetic measures of trait evolution with sophisticated analyses of lineage diversification rates, this research will investigate the explicit role of hybridization in the early stages of an adaptive radiation.