Doffitt, Chris , Wallace, Lisa .
Phylogeographic structure in a wide-ranging species, Amsonia ciliata (Apocynaceae).
Floristic studies of the southeastern U.S. have shown that it is rich in plant diversity,and phylogeographic studies have identified numerous refugial locations common to plants, as well as animals. However, there is still much to learn about the roles of abiotic factors and geologic barriers in generating this diversity. Ideal study organisms for this type of research would have large ranges in a variety of habitats across this region. Amsonia ciliata (Apocynaceae) is an example of one such species, with a range extending from Texas to South Carolina. Populations occur discontinuously across this region and typically in xeric habitats, including glades and sandy soils of the Gulf Coastal Plain. Considering the variation in habitat types,one would expect some degree of local adaptation. In addition, the patchy distribution of this species suggests that landscape and ecological barriers restrict gene flow between populations, which may promote population divergence. To test the hypothesis that population genetic structure exists, we utilized AFLP markers on samples from 11 populations of A.ciliata throughout its range. The Mississippi River was expected to be a barrier to gene flow. Also, populations on each side of this geographic barrier growing on similar substrates should be more closely related to one another. An AMOVA of the populations east and west of the Mississippi River suggests that there is more variation among populations(Fst= 0.169; p=0.0001) than among regions (Fst= 0.032; p= 0.0001). A STRUCTURE analysis suggests that there is strong structure in populations that occur on remnant sand dunes in central Georgia, which interestingly also exhibits variation in morphology when compared to other A. ciliata populations. This analysis also suggests that populations from glades in Alabama and Arkansas are genetically divergent from other populations in the eastern part of the range. These glades are notable as reservoirs for unique and newly described species. These results imply that, while there is genetic structure among populations, it may not be due to major geographic barriers, such as the Mississippi River. Instead, genetic structure may be due to reproductive isolation and genetic drift at local scales. This work contributes to the growing phylogeographic literature on southeastern plants. In addition to providing important information on distinctiveness and distributions of morphologically variable populations of A. ciliata, this work will contribute to setting conservation priorities and implementing management practices for A. ciliata and other glade endemics.
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1 - Mississippi State University, Department Of Biological Sciences, PO Box GY, Mississippi State, MS, 39762-5759, USA
2 - Mississippi State University, PO Box GY, Mississippi State, MS, 39762, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Franklin A/Hyatt
Date: Tuesday, July 10th, 2012
Time: 10:00 AM