The Influence of Life History Traits on Patterns of Holocene Migration and Geographic Distribution of Forest Herbs in the Berberidaceae, Liliaceae and Ranunculaceae.

The range size and range edges of plant species are believed to be controlled by environmental factors and life history characteristics. Among life history traits, seed dispersal mode is an important autecological characteristic that has the potential to influence various aspects of species interactions with the environment, yet its role in determining patterns of distribution and abundance on large geographic scales is not well understood. This study will examine the influence of seed dispersal mode in determining patterns of postglacial migration, northerly range extent and the location of modern range edge for an assemblage of six herbaceous species with differing seed dispersal modes in the deciduous forests of eastern North America. The primary research approach will involve a comparative phylogeographic analysis of congeneric or closely related forest herb taxa with differing seed dispersal modes. Genetic analysis of chloroplast DNA variation across species ranges will be used to reconstruct the history of population fragmentation during Pleistocene glaciations of North America and the subsequent expansion of populations during the Holocene. Comparative analyses of migration patterns and population genetic structure among plant taxa with differing seed dispersal modes will be used to assess the improtance of seed dispersal mode in determining rates and patterns of Holocene recolonization.The project will involve a comparative phylogeographic study of six forest herb taxa: Actaea pachypoda, Cimicifuga racemosa, Jeffersonia diphylla, Podophyllum peltatum, Uvularia grandiflora and Polygonatum pubescens. Several of these forest herb taxa occur at the Coweeta LTER; these species would be the focus of sampling during my visit to the site. Phylogeographic analyses utilize variation in molecular markers to study geographic patterns of relatedness between populations. In plants, chloroplast DNA (cpDNA) is commonly used because it is often variable at the population level and is maternally inherited (i.e., via ovules); consequently, it can provide a direct measure of migration via seed dispersal. By screening for cpDNA loci that exhibit variation among plant specimens from across a species range, it is possible to develop a phylogeny which can be geographically referenced to infer the history of population fragmentation and expansion. For this study, leaf samples of approximately 2 x 2 inches would be collected from 5-20 individuals of each of the focal species at each of 30-40 population sites across the southeastern United States, Midwest and Northeast. One to three populations of each of the focal species occuring at Coweeta LTER would be identified in consultation with Coweeta LTER staff and sampled during a one to two day period in June of 2003. Leaf samples would be collected from 5 - 20 individuals in each of these populations. The sampling procedure should not substantially harm plants sampled; no plants would be collected in whole, dug up or otherwise disturbed or destroyed. The leaf samples from these populations would be transported to Cornell University with other leaf samples from the southeastern United States for processing and screening for cpDNA polymorphisms. The cpDNA haplotypes identified by this analysis and analysis of specimens from other regions of the eastern United States will be geographically referenced to examine patterns of cpDNA variation in relation to species range; specifically, the research will reconstruct patterns of Holocene migration for the selected focal species in eastern North America and infer locations of refugia and/or southern population centers during the glacial maximum. Comparative analysis of these data among related taxa with differing dispersal modes will evaluate the role of seed dispersal in driving rates and patterns of migration, and resultant range edge-range size dynamics