Distribution of Genotypes Within and Among Taeniatherum caput-medusae (Poaceae) Populations From Eastern Washington: Investigation of the Invasion Process at a Local Scale

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Stephen J. Novak


Biological invasions are defined as the introduction, establishment and spread of an organism into a region where it did not previously occur; such events are often associated with severe ecological and economic consequences. Propagule pressure, the number of individuals (propagules) introduced into a new range, has recently emerged as a predictor of establishment success and is believed to increase the likelihood of invasion. High propagule pressure is also described by the term multiple introductions, which can increase the chance of introducing pre-adapted genotypes, increase the amount of genetic variation within populations and increase the likelihood of adaptive evolution. Taeniatherum caput-medusae is an annual, highly self-pollinating grass species that is invasive to the western United States. Previous genetic analyses using enzyme electrophoresis detected five multilocus genotypes (MLG) in the relatively small geographic area of Eastern Washington, which suggests that multiple introductions have occurred in this region. The goal of this study is to analyze 59 additional populations of T. caput-medusae from Eastern Washington using this same genetic marker. Results of this study will provide a better understanding of the genetic consequences of the multiple introductions into this relatively small geographic area.

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