Douglas, Norman , Peet, Robert , Allen, Martin , Thomas, David , Xiang, Qiu-Yun (Jenny) .
Species delimitation and phylogeography in the Nyssa sylvatica complex (Nyssaceae) of Eastern North America.
Phylogeographic analyses of tree species provide important insights into the origin and evolution of regional forest and plant communities. Southeastern North America represents one of the most species-diverse regions of North America, but few phylogeographic studies have concerned plants of this region, and have not revealed congruent patterns. Nyssa sylvatica (Nyssaceae) is a common deciduous tree found of temperate forests of eastern North America, from Maine to Florida, Texas, and Mexico. The taxonomy of the group has been controversial due to complex morphological variation: N. sylvatica has occasionally been considered to include N. ursina and N. biflora. We samppled 77 populations of N. sylvatica, N. biflora, and N. ursina from across their distributional range. Data included cpDNA (trnH-K), and two nuclear regions (antR and LEAFY). We evaluate competing taxonomic concepts of this group and examine phylogeographic patterns by reconstructing gene genealogies, testing for isolation by distance, and employing coalescent analyses. Each data partition was consistent with a close alliance between N. biflora and N. ursina relative to a paraphyletic N. sylvatica, and tests for isolation-by-distance were not significant, consistent with the existence of at least two species. The phylogenetic pattern of chloroplast and nuclear genes differs, suggesting potential distinct patterns of gene flow via seeds and pollen in the species complex. The utility of recently developed methods for coalescent hypothesis testing (i.e. BEST) will be discussed as they relate to the delimitation of species in the complex. No apparent phylogeographic barriers were found, although increased sampling in selected areas could reveal refugia. The phylogeographic pattern in the N. sylvatica group appears to differ from those found in other woody plants in the eastern US (e.g., Fagus grandifolia, Acer rubrum).
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1 - North Carolina State University, Department of Plant Biology, Campus Box 7612, Raleigh, NC, 27695, USA
2 - University of North Carolina, Department of Biology, Campus Box 7612, Chapel Hill, NC, 27599
Presentation Type: Oral Paper:Papers for Topics
Date: Monday, July 28th, 2008
Time: 2:30 PM