Systematics Section / ASPT
Burge, Dylan .
Molecular systematics of the genus Garrya (Garryaceae): a phylogeny based upon nuclear gene sequences.
THE genus Garrya Dougl. ex Lindl. (Garryaceae) comprises approximately fifteen species of wind-pollinated, dioecious, evergreen trees and shrubs distributed in North America (including Mexico), Central America, and the Caribbean Islands. The genus contains a pair of allopatrically distributed subgenera that are delimited on the basis of flower and inflorescence morphology. Subgenus Garrya, which is restricted to the western United States and northern Mexico, with one outlying species in Guatemala, contains several partly sympatric and morphologically intergrading species. In order to understand the relationships among species within subgenus Garrya, and test for genetic introgression and geographic structure among populations, I obtained up to eight samples from six of the seven members of subgenus Garrya, several members of the second subgenus of Garrya, one member of the hypothesized sister genus of Garrya, Aucuba, and several other species of asterids. From these collections I sequenced non-coding regions of two nuclear genes. Phylogenetic reconstructions using parsimony and maximum likelihood approaches on the combined data set provided results that support the sister group relationship between the subgenera of Garrya, but provide little resolution at the level of species within subgenus Garrya. Overall, the nuclear introns used in this study show little variation within species from subgenus Garrya, both between putative species and within single species distributed over large geographic areas. This result may indicate that these species are young relative to the remainder of the genus, and represent a recent radiation in western North America. Genetic introgression between recently diverged species may also contribute to this lack of resolution, but is unlikely to have resulted in the observed homogeneity of these species, especially over large allopatric regions.
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1 - Duke University, Department of Biology, 139 Biological Sciences Building, PO Box 90338, Durham, North Carolina, 27708, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, August 1st, 2006
Time: 2:30 PM