Genetic Analysis of Downy Brome (Bromus tectorum) and Medusahead (Taeniatherum caput-medusae): Management Implications1

Genetic analyses of invasive plants can provide information concerning the introduction dynamics of invasive species, the parameters associated with range expansion, the mechanisms of dispersal in the new range, and the identification of source populations. This information can give managers insights into the range of genotypes (and associated phenotypes) introduced, whether these genotypes may have experienced intermixing during range expansion, and the most efficacious locations in the native range to seek biological control agents. The invasive grasses downy brome and medusahead are now the predominant vascular plant species of degraded rangelands throughout arid and semiarid portions of western North America. In this article, I provide background information on the biology and history of introduction of downy brome and medusahead, summarize results of the allozyme analysis of populations of both species, and indicate the importance of these data to the management of invasive plant species. In addition, these data will be used to assess the introduction and spread of both downy brome and medusahead in their new ranges.Nomenclature: Downy brome, Bromus tectorum L. #3 BROTE; medusahead, Taeniatherum caput-medusae (L.) Nevski # ELYCM.Additional index words: Allozymes, genetic markers, invasive plants, multiple introductions.Abbreviations: Got-4c, glutamate oxaloacetate transferase, locus 4, “c” allele.