Marchini, Gina , Cruzan, Mitchell .
Evolution of an Aggressively Invasive Plant; Evidence for Purging Genetic Load in Brachypodium sylvaticum.
Invasive plants decrease biodiversity and alter community dynamics as they take over niches utilized by native species. Interactions of the ecological and evolutionary dynamics that underlie the process of invasion can be complex, but are essential to understand to control the spread of weeds.Brachypodium sylvaticum (slender false brome) is a perennial bunch grass invasive to the Pacific Northwest region of North America. As B. sylvaticum spreads secondary bottlenecks and lag phases delay population growth at the edge of the expanding range before rapid expansion resumes. Lag phases are hypothesized as due to homozygosity of self-fertilizing populations experiencing loss of fitness until sufficient gene flow or purging of deleterious alleles occurs. Our initial experiments indicate that vigor ofplants from newly-colonized populations is positively associated with population heterozygosity. This suggests that range expansion may be slowed by inbreeding depression; however, there were some exceptional populations that were homozygous with highly vigorous plants. We tested levels of inbreeding depression from six populations to assess whether purging of genetic load was occurring during range expansion by comparing the growth of seedlings from self and far-outcross (inter-population) crosses. We found evidence that inbreeding depression was substantially reduced in homozygous populations that were close to the edge of the expanding range. Simulations suggest that purging may be optimized by crossing scenarios that alternate generations of selfing and outbreeding through intermittent gene flow. These expected changes in metapopulation dynamics and rates of range expansion have major implications for changing management strategies for invasive plants as the evolution of highly vigorous selfed offspring occurs.
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Cruzan Lab Web Page
1 - Portland State University, Department Of Biology, PO BOX 751, PORTLAND, OR, 97207, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Delaware B/Hyatt
Date: Tuesday, July 10th, 2012
Time: 11:00 AM