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Title: Patterns of introduction and adaptation during the invasion of Aegilops truncialis (Poaceae) into Californian serpentine soils

Author
item MEIMBERG, HARALD - Centro De Investigacion
item MILAN, NEIL - Colorado State University
item KARATASSIOU, MARIA - Foreign Agricultural Service (FAS, USDA)
item Espeland, Erin
item MCKAY, JOHN - Colorado State University
item RICE, KEVIN - University Of California

Submitted to: Molecular Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2010
Publication Date: 12/1/2010
Citation: Meimberg, H., Milan, N.F., Karatassiou, M., Espeland, E.K., Mckay, J.K., Rice, K.J. 2010. Patterns of introduction and adaptation during the invasion of Aegilops truncialis (Poaceae) into Californian serpentine soils. Molecular Ecology. 19(23): 5308-5319. doi: 10.1111/j.1365-294X.2010.04875.x

Interpretive Summary: How do invasive species adapt to new environments? In California, barbed goatgrass (Aegilops triuncialis), an annual grass from the Mediterranean and Middle East, is invading low-fertility serpentine soils in California. These soils are home to a diverse array of native plants that may be threatened by the introduction of this invasive plant. In this study, we compared invasive populations in California to populations within the native range. We found that the plants in California comprise only three genotypes, and each type has a different trait that explains its success on serpentine soil. While all California populations do better on serpentine soil compared to more fertile soils, only a few European populations are able to do well on serpentine soil. It is possible that multiple introductions of plants from Europe allowed some plants already suited to serpentine soil to enter California and to invade this soil type.

Technical Abstract: - Multiple introductions appear to be playing a prominent role to explain the success of biological invasions. One often cited mechanism is the prevention of a genetic bottleneck by the parallel introduction of several distinct genotypes, which in turn provides the heritable variation that can allow for local adaptation. Here we show that multiple introductions promoted the invasion of Aegilops triuncialis into serpentine habitats by providing differentially adapted genotypes. - Using microsatellite markers we investigated the genetic structure of multiple populations of Ae. triuncialis, invasive in serpentine soils in California, in comparison to native accession. In addition we determined flowering time and fitness on loam and serpentine for all samples. - The invasion involves three independent introductions. All Californian samples showed higher fitness on serpentine than on loam. The three independent introductions showed different pathways towards serpentine adaptation. The majority of Eurasian accessions showed a fitness decrease on serpentine soil but some individuals achieved high fitness due to similar flowering time phenology to California populations. - Our results suggests that the adaptations of invasive populations in California to serpentine may in fact be preadpatations, where multiple introductions provided the requisite variation to be sorted by the new habitat.