DISSERTATION RESEARCH: Out of the Bushes and Into the Trees: Alternative Approaches to a Problematic Lamiaceae Phylogeny

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The mint family (Lamiaceae) is among the most diverse and economically important families of flowering plants, with many species used in traditional medicines or serving as important sources of timber, culinary herbs and spices, and essential oils. The extreme morphological complexity of the Lamiaceae, combined with the large number of species spanning diverse habitats, presents many taxonomic, or classification, problems; it is often difficult to distinguish closely related species. Numerous molecular studies have been published recently to help revise classifications?studies that reconstruct phylogenetic (genealogical) relationships among species using information from the genetic code (DNA). However, these analyses regularly yield patterns of unresolved relationships, and standard approaches used to resolve phylogenies, such as the reasonable addition of species and genes into the analyses, have been largely ineffective. The proposed research uses Lamiaceae as a case study to evaluate new, alternative approaches for resolving difficult phylogenetic problems and explores the limits of how evolutionary relationships can be efficiently and cost-effectively reconstructed for large groups of organisms. These approaches involve large-scale DNA (or genome) sequencing and new computational methods for phylogenetic inference. The research represents a necessary step towards resolving difficult phylogenetic problems in Lamiaceae and will help move mint systematics ?out of the bushes and into the trees??that is, to resolve clear evolutionary trees from the current unresolved ?bush? patterns.The proposed research is at the forefront of systematic biology, combing field botany with recent advances in computational biology and molecular genetics, and it has the potential to demonstrate the efficacy of new, cross-disciplinary approaches to resolving difficult phylogenetic problems that can be applied to other problematic groups of plants and animals. The results of this study will: produce the first chloroplast genomes for Lamiaceae; contribute insights into the evolutionary history and biogeography of North American mint groups; and provide an essential framework for a much-needed taxonomic revision. Moreover, because this study requires field exploration and population sampling, it will facilitate the discovery and recognition of new mint species or important sources of genetic diversity that may warrant protection by government agencies or conservation organizations.