Recent Topics Posters
Rosenthal, David M , Ramakrishnan, Alisa , Cruzan, Mitchell, B .
Hybridization, differentiation and invasion of the northwest by Brachypodium sylvaticum (Huds.) Beauv.
BRACHYPODIUM sylvaticum, or slender false brome, is a Eurasian perennial bunchgrass introduced into Oregon for forage research. Early records suggest that it escaped cultivation near Eugene or Corvallis OR, sometime before 1939. Within the last few decades it has become widespread in northwestern Oregon, and in several locations it is an aggressive invasive weed. It has recently colonized California Redwood forests. Brachypodium sylvaticumís recent range expansion presents a unique opportunity to study the spread and evolution of a newly invasive species. In this study we are attempting to 1) identify the origins of this noxious weed, 2) test the hypothesis that its success may have been facilitated by intraspecific hybridization between previously allopatric populations and 3) determine if the invasive populations are genetically differentiated. Analysis of chloroplast DNA variation in native and introduced ranges indicate that all the US populations sampled have a unique haplotype which is also common throughout Europe. Nuclear microsatellite data segregate US individuals into three distinct clusters suggesting that US populations are an admixture from two or three western European sources. Assignment tests corroborate the admixture hypothesis indicating that some individuals are of intraspecific hybrid origin. It is also likely that California populations were colonized by Oregonian individuals. We tested if Oregon populations are genetically differentiated by measuring growth, phenology and allocation traits using a half-sib design. Significant family within population effects for these traits indicate the differences are heritable. If the trait differences among US populations are adaptive then selection may facilitate the invasion of B. sylvaticum in differing habitats. Taken together these data suggest that B. sylvaticum in the U.S. arose from several founding European sources. Moreover, intraspecific hybridization between previously allopatric populations may have played a role in the formation of invasive genotypes in Oregon.
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1 - Portland State University, Biology, P.O. Box 751, Portland, OR, 97207, USA
Presentation Type: Recent Topics Poster
Location: Auditorium/Bell Memorial Union
Date: Tuesday, August 1st, 2006
Time: 12:30 PM