Martin, Michael , Brush, Grace , Zimmer, Elizabeth .
Temporal changes in genetic structure of common ragweed (Ambrosia artemisiifolia) in its native range.
Ambrosia artemisiifolia (common ragweed; Asteraceae, Compositae) is a pioneer weed native to North America. Detailed palynological records from sediment cores indicate that this species was relatively uncommon until European colonization of North America. While settlers deforested the landscape on a massive scale, ragweed populations grew dramatically. The species then became an aggressive global invasive that has established populations in Europe, Australia, China, Japan, Russia, Israel, and beyond. We hypothesize that this population expansion has been coupled with admixture of previously isolated populations, increasing genetic diversity and priming this species for invasion upon its introduction to novel landscapes. We report preliminary findings of an ongoing study of phylogeographic structure revealed through an analysis of polymorphisms in three intergenic chloroplast (cpDNA) spacer regions and at several nuclear microsatellite loci. With the goal of reconstructing extinct populations from historical herbarium specimens collected up to 120 years ago, our attempts to amplify moleculer markers have been successful, yielding unambiguous cpDNA sequences from nearly 90% of sampled specimens. Ongoing work with herbarium collections will be used to directly compare population genetic structure in the time since anthropogenic disturbance. Our data show that diversity evident among extant North American populations should make it possible to trace invasion routes by assigning worldwide invasive populations to their geographic origins in the native range.
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1 - Johns Hopkins University, Geography and Environmental Engineering, 313 Ames Hall, 3400 North Charles Street, Baltimore, MD, 21218, USA
2 - Smithsonian National Museum of Natural History, Botany, Museum Support Center, 4210 Silver Hill Road, Suitland, MD, 20746, USA
Presentation Type: Oral Paper:Papers for Topics
Location: 556A/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 8:30 AM