Wallace, Lisa , Doffitt, Christopher .
Phylogeographic patterns of Trillium cuneatum and Trillium stamineum within the Black Belt and Jackson Prairie Regions of Mississippi and Alabama.
It has been hypothesized that the high levels of diversity noted for the Southeast are related to the restriction of species' ranges and subsequent migrations during and after the last glacial period. Numerous refugia have been proposed in the Southeast, and many of these have been supported by empirical phylogeographic studies of plants and animals. Trillium (Melanthiaceae), a highly diverse genus in the Southeast, includes many species that are locally endemic. Given this pattern, it has been hypothesized that vicariance associated with the restriction of populations in pockets of suitable habitat in association with local adaptation have been leading causes of evolutionary diversification within Trillium. In this study, we examined DNA sequence variation within two Trillium species, T. cuneatum and T. stamineum, in eastern Mississippi and western Alabama to evaluate the potential for local differentiation. Forested regions where these species occur are separated by the regions of the Black Belt and Jackson Prairies, which are not considered to contain suitable habitats for Trillium. We hypothesized that T. cuneatum and T. stamineum would exhibit similar patterns of genetic structure and that populations separated by the prairie patches would be most divergent. Based on variation in the trnL intron and trnL-trnF intergenic spacer region of the chloroplast genome we identified a high level of haplotypic diversity in both species - five and four haplotypes in T. cuneatum and T. stamineum, respectively. Additionally, there is strong regional structure for both species with very little polymorphism within populations, suggesting that gene flow by seed dispersal is quite limited in both of these species. This pattern of structure was not wholly consistent with the historical extent of the prairies. Other landscape features, such as rivers, may have served as additional barriers to dispersal. These results corroborate previous studies and further point to survival in multiple refugia, possibly located in southern Alabama and/or southern Mississippi prior to recolonization of present-day populations.
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1 - Mississippi State University, Biological Sciences, 295 Lee Blvd., Mississippi State, MS, 39762, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Lindell A/Chase Park Plaza
Date: Monday, July 11th, 2011
Time: 11:30 AM