Waselkov, Katherine , Olsen, Kenneth , Schaal, Barbara .
How does a weed arise? Genetic evidence for the origin of the Midwestern agricultural weed Amaranthus tuberculatus (Amaranthaceae).
Many researchers are interested in the question of how pest plants adapt to agricultural practices, but few studies have investigated the origin of a recently arisen crop field weed. Amaranthus tuberculatus, waterhemp, is a native riverbank pioneer that was first observed invading Midwestern soybean and cornfields around 1950, and has since become a major agricultural problem in the region. We hypothesize that secondary contact and hybridization between diverging geographical varieties of the species in the Mississippi Valley region, possibly facilitated by land use changes, led to the development of a "weedy" variety of the species. Using SSR markers, we have genotyped agricultural and riverbank populations of waterhemp from across the species' range. Despite little genetic differentiation at a local scale, we find evidence of two ancestral genetic clusters within the species. A previous hypothesis, that introgression from the weedy congener Amaranthus hybridus was involved in waterhemp's adaptation to crop fields, is not supported. Analyses using the program IMa and Slatkin's private alleles method will allow us to evaluate population genetic models of the historical origin of weedy A. tuberculatus.
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1 - Washington University in St. Louis, Biology, 1 Brookings Drive, Campus Box 1137, Saint Louis, MO, 63139, USA
2 - Washington University, BIOLOGY DEPT, BOX 1137, 1 BROOKINGS DRIVE, St. Louis, MO, 63130-4899, USA
3 - Washington University, Department Of Biology, CAMPUS BOX 1137, 1 Brookings Drive, St. Louis, MO, 63130-4899, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Portland Room/Chase Park Plaza
Date: Tuesday, July 12th, 2011
Time: 8:45 AM