Doctoral Dissertation Research: Identification of Glacial Refugia by Phylogeographic Analyses of the Forest Understory Plant Species, Trillium Cuneatum

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The description and interpretation of geographic patterns of genetic variation have occupied a central position in plant evolutionary biology. Historical, paleoecological, and biogeographical perspectives often have not been included in these interpretations, however. With the availability of arrays of molecular genetic markers combined with advanced analytical procedures, it is now possible to couple biogeographical and paleoecological perspectives with population genetic and phylogenetic analyses. This approach is embodied in the discipline of phylogeography (a subdiscipline of biogeography). The goal of this doctoral dissertation research project is to combine analyses of maternally transmitted chloroplast DNA and bi-parentally inherited allozyme markers to investigate the phylogeography and glacial refugial history of the forest understory species, Trillium cuneatum (Melanthiaceae). This study will demonstrate how populations are related across the species' geographic range, allowing inference of past refugia and post-glacial colonization patterns. Objectives of this project are: (1) to identify the number and locations of glacial refugia; (2) to infer patterns of post-glacial colonization routes; and (3) to describe the degree of overlap and intra-population polymorphism of refugial lineages.Determination of past range contractions and refugial expansions has important implications for understanding the biogeographical and evolutionary processes that have shaped the contemporary distribution of biodiversity. By simultaneously examining the spatial and temporal distribution of genetic diversity, this project will testify to refugial locations during the last glacial maximum and will identify ancient migration patterns following this period. The research therefore will provide a historical biogeographical context for the interpretation of contemporary genetic divergence. This project also complements studies of Southern Appalachian biodiversity (conducted by the National Park Service) by providing insights into the vegetation history and biodiversity of the southeastern U.S. For example, the question of whether widespread species spread into the Southern Appalachians after the last glacial maximum or whether these species originated from small in situ refugia has important implications for the effective management of the rich southeastern flora. Furthermore, by developing insights into the processes that have shaped contemporary genetic variation, this study should prove useful in predicting biotic responses to future global climatic changes. Regional and global patterns of climatic change inferred from the Quaternary and early Holocene fossil records coupled with detailed genetic analyses will identify similarities and differences between species in their response to climate change. The accumulation of such information may yield analogues for future climatic change, and, thus assist the evaluation of the anticipated changes. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.