Colloquia: Emerging Results from Studies of Gymnosperms on the Tree of Life II
Li, Jianhua , Gao, Lianming , Mathews, Sarah .
Phylogeny, ancestral polymorphisms, and introgression in species of Taxus.
Species of Taxus (e.g., the common yew, T. baccata) are shrubs and small to large trees and have long been cultivated as ornamentals in Europe and North America. They have attracted public attention owing to the discovery of cancer-inhibitory taxol in the bark of the pacific yew T. brevifolia. Taxonomically, however, the number of species of Taxus ranges from one to over 50 depending on the author. Recent quantitative morphological and molecular analyses of the three varieties of the T. wallichiana complex suggest that T. wallichiana occupy mostly discrete geographic ranges with some sympatry east of the Tanaka-Kaiyong line and the Sichuan Basin, China, indicative of limited gene flow among the taxa. In this study we obtained DNA sequence data of both plastid (ccsA, rpoA, rpoB, rpoC, matK, and psbA-trnH) and nuclear (NEEDLY) regions from all species of Taxus to test previous hypotheses of interspecific relationships in the genus and to gain further insights into the gene flow between species of Taxus in a global scale. Both plastid and nuclear sequence data support the closer relationship of Taxus canadensis to Eurasian species than to other North American species. North American species do not form a clade as suggested by the nrDNA ITS data, although T. floridana and T. globosa are robustly supported as sister taxa by the plastid data. Instead, T. brevifolia is sister to the clade containing the remaining species of the genus. NEEDLY sequences from two populations of T. globosa occur within the Eurasian clade, suggesting a complex evolutionary history of the gene in Taxus. Phylogenetic comparisons and simulation analyses under the coalescent assumptions suggest that both incomplete lineage sorting and introgression may have occurred in the evolutionary history of Taxus.
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1 - Hope College, Biology Department, 35 E 12th St., Holland, MI, 49423, USA
2 - Kunming Institute of Botany, Chinese Academy of Sciences, Heilongtan, Kunming, Yunnan , 650204, China
3 - Harvard University, Arnold Arboretum, Harvard University Herbaria, 22 Divinity Avenue, Cambridge, MA, 02138, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Ballroom C/Convention Center
Date: Monday, August 2nd, 2010
Time: 3:00 PM