Schenk, John J. .
Biogeographic Diversification of Mentzelia Section Bartonia (Loasaceae) in the North American West.
Aridification of the North American West is considered to have spurred plant migrations from the Miocene to the Recent as species invaded newly formed habitats and floristic assemblages. The 51 species of Mentzelia section Bartonia inhabit most floristic regions within the North American West, providing an opportunity to investigate migration and subsequent diversification among western floras. This study applied statistical phylogenetic methods to molecular data to ask (1) how many migration events have occurred, (2) the directions of these migrations, and (3) whether migration events between mesic and arid habitats have been asymmetrical. Species were scored as occurring in the Great Basin, Mohave, Sonoran, or Chihuahuan deserts, the Rocky Mountains, the North American prairie province, or the Chile-Patagonian region in South America. Ancestral ranges and transitions were then estimated with parsimony, likelihood, and stochastic mapping methods, and model fitting was used to address question (3). Multiple transitions were inferred, especially to and from the Great Basin and Rocky Mountains. The ancestral area for section Bartonia was estimated to be either the Great Basin or the Rocky Mountain province. A single dispersal event from the prairie province to the Chile-Patagonian region was inferred. The Mohave and Chihuahuan deserts exchanged more migrations with the Great Basin and Rocky Mountains, respectively, than with the Sonoran Desert. The Sonoran Desert exchanged more migrations with the Great Basin than with other floras. The North American prairie has exchanged migrants with the Great Basin, suggesting subsequent northward diversification. These results implicate the Great Basin and Rocky Mountains as important sources and recipients of migrants in section Bartonia. Within these regions, a greater transition rate from mesic to arid than from arid to mesic habitats was recovered. Additionally, model fitting suggests that species diversity is greater in the Great Basin and Sonoran Desert and lower in the Rocky Mountains, prairie province, and other southwest deserts than would be expected by the modern flora’s age alone.
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1 - Florida State University, Dept. of Biological Science, Tallahassee, FL, 32306, USA
North American deserts
Presentation Type: Oral Paper:Papers for Topics
Location: 551A/Convention Center
Date: Monday, August 2nd, 2010
Time: 11:00 AM