Systematics Section / ASPT
Egan, Ashley N. , Crandall, Keith A. .
Phylogenetics and Biogeography of tribe Psoraleeae (Leguminosae) Based on Nuclear and Chloroplast DNA Markers.
The Psoraleeae tribe (Leguminosae) spans the North American continent, comprising some 45 plant species. Many of these species are endemic, this status contributing to an elevated risk of extinction. Understanding the biodiversity and classification of a group is paramount to conservation studies. This study aims to quantify the level of biodiversity within North American Psoraleeae and test classification schemes for the tribe. Classifications have been proposed, from a single genus Psoralea, purported by Bentham (1865), to 5 genera suggested by Grimes (1990), namely Pediomelum, Psoralidium, Hoita, Rupertia, and Orbexilum. This study represents the first molecular systematic work within Psoraleeae. Phylogenetic analysis based on the nuclear Internal Transcribed Spacer (ITS) and two chloroplast DNA markers, the trnS-trnG and trnL-trnF intergenic spacers, were used to assess evolutionary relationships. The three markers were analyzed in a combined analysis under Maximum parsimony and Phylogenetic Mixed Models implemented within a Bayesian framework. Generic division similar to that proposed by Grimes is supported, but only moderate evidence for species relationships was found, suggesting a rapid radiation within Pediomelum, the largest genus. Levels of biodiversity, as assessed by nucleotide diversity, are exceptionally low with some species differing by only 2 nucleotides out of over 2500. This low level of genetic diversity may suggest taxonomic revision within the tribe.
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1 - Brigham Young University, Microbiology and Molecular Biology, 753 Widb, Provo, Utah, 84602, USA
2 - Brigham Young University, Department of Integrative Biology, 401 Widb, Provo, Utah, 84602, USA
Presentation Type: Poster
Location: Salon C, D & E - Gov Ballroom/Hilton
Date: Tuesday, August 16th, 2005
Time: 12:30 PM