Genetic Diversity in Native Populations of Taeniatherum Caput-Medusae Subspecies Asperum and Subspecies Crinitum (Medusahead): Identifying the Source Populations of an Invasion

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Stephan Novak


Biological invasions occur when organisms are introduced into a new range where they persist and spread, and often these events have severe ecological and economic consequences. Taeniatherum caput-medusae (medusahead) is an annual, self-pollinating grass with a broad geographical distribution across Eurasia. Within its native range, three subspecies have been identified: subspecies asperum, subspecies crinitum and subspecies caput-medusae. The grass is invasive in six states (California, Idaho, Nevada, Oregon, Utah and Washington) in the Western United States (U.S.). Previous genetic analyses of invasive populations of subspecies asperum identified seven multilocus genotypes, and one multilocus genotype for subspecies crinitum. Using enzyme electrophoresis, we assessed the genetic diversity within 15 populations of subspecies asperum from Bulgaria, Ukraine and Turkey, and six populations of subspecies crinitum from Ukraine and Turkey. These data can be used to determine the source populations for the invasion of both subspecies in the western U.S. Native populations of subspecies asperum have higher amounts of genetic diversity, compared to native populations of subspecies crintum. Many of the 15 populations of subspecies asperum we analyzed have multilocus genotypes that match the genotypes previously detected among invasive populations, suggesting that source populations may be distributed over a broad geographic area, from Eastern Europe to Turkey. All six populations of subspecies crinitum we analyzed have the same multilocus genotype, and it matched the genotype observed in the western U.S. These results indicate that important insights into the invasion process can be obtained by analyzing native and invasive populations within the same experimental design.

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