Wall, Wade , Douglas, Norman , Xiang, Qiu-Yun (Jenny) , Hoffmann, William , Wentworth, Thomas , Gray, Janet , Hohmann, Matthew .
Incongruence between morphological, ecological, and geographical differences and genetic structure: genetic analysis of Pyxidanthera (Diapensiaceae) using AFLP markers.
Pyxidanthera (Diapensiaceae ) has been described as either a monotypic genus with two morphologically distinct varieties, or as including two species. Pyxidanthera barbulata var. barbulataoccurs in a variety of habitats in the Atlantic Coastal Plain from South Carolina to New York, while the more geographically limited Pyxidanthera barbulata var. brevifolia occurs in extremely xeric sites in the Sandhills region of North Carolina and South Carolina. The geographical, ecological, and morphological differences suggest either allopatric divergence followed by secondary contact in the Sandhills, or a more recent separation of the two taxa in the Sandhills. We conducted a genetic analysis using AFLP markers to evaluate these hypotheses and to explore the population genetic structure of the genus. We collected tissue samples from 15 Pyxidanthera barbulata var. barbulata sites and 20 Pyxidanthera barbulata var. brevifolia sites from across the ranges of both taxa. Three AFLP primer pairs resulted in 347 polymorphic bands, with the two taxa having comparable levels of genetic variation. AMOVA results indicate that the majority of the genetic variation occurs within sites, with taxonomic grouping and geographic location explaining very little of the genetic variation found in Pyxidanthera. The most probable number of populations (K) found by the program STRUCTURE did not correspond to any geographic or taxonomic groupings. Finally, we found no evidence for isolation by distance. Taken together, these results suggest that neither allopatric divergence followed by secondary contact nor in situ genetic divergence of Pyxidanthera barbulata var. brevifolia occurred. Future work investigating chloroplast sequence data may shed light on the role of gene flow by seeds in generating the observed patterns, and allow us to understand the conflicting signals sent by the ecological and morphological data versus the genetic data.
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1 - North Carolina State University, Department of Plant Biology, Campus Box 7612, Raleigh, NC, 27695, USA
2 - United States Army, Directorate of Public Works, Endangered Species Branch, Fort Bragg, NC , 28310, USA
3 - US Army Corps of Engineers, US Army Engineer Research and Development Center, PO Box 9005, Champaign, IL, 61826, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Cottonwood B/Snowbird Center
Date: Monday, July 27th, 2009
Time: 3:30 PM