Determining the evolutionary relationship between the seed beetle genus Acanthoscelides (Chrysomelidae: Bruchinae) and its host plant in genus Astragalus

A fundamental question in biology is the relative roles of ecology and geography in driving intraspecific differentiation and, by extension, speciation. Astragalus-feeding seed beetles in the Acanthoscelides aureolus species group are widespread in western North America, but taxonomic limits among the eight described species are very difficult to determine. This appears to be due to multiple interacting factors: very high levels of genetic and morphological variation within individual species; a poor understanding of whether or not this variation is correlated with host use or diet breadth; and a poor understanding of how either genetic or morphological variation is structured at geographic levels. In this analysis we present results of a comprehensive interspecific phylogeographic survey of this group based on mitochondrial DNA and the results of a preliminary survey of microsatellite variation in this group. In addition, we present preliminary results of population genetic analyses at more local levels in order to evaluate the relative roles of host plant association and geography in structuring patterns of genetic variation within both Ac. aureolus and Ac. pullus.