Variation in feeding behavior and performance among geographic populations of the Colorado potato beetle, Leptinotarsa decemlineata

The Colorado potato beetle, Leptinotarsa decemlineata, is a cosmopolitan pest species with a global distribution extending throughout the Northern Hemisphere. The beetle represents the most damaging potato plant defoliator among insect pests. Despite its global pest status, beetles populations found within their putative region of origin, central Mexico, are unable to complete their life cycle on potato. In an attempt to understand the geographic variation in pest behavior and the origin of the derived pest lineage, we conducted a study to investigate the variation in feeding preference and performance on both ancestral , Solanum rostratum, and derived, Solanum tuberosum, host plants. We sampled beetles from three Mexican states and two US regions: Oaxaca, Jalisco and Texcoco and northern Vermont and Kansas, respectively. Dependent variables included host acceptance, growth rate and host choice for individual beetles collected from each region. Vermont beetles exhibited both greater acceptance and performance for both host plants and failed to show any marked preference for either S. tuberosum or S. rostratum. Furthermore, Vermont beetles displayed higher growth rates on ancestral hosts when compared with their natal host. Beetles collected from populations within Texcoco, MX, exhibited both higher growth rates and host acceptance among all Mexican populations. These results suggest that the emergence of the pest lineages of L. decemlineata represents a host expansion rather than a host shift. Variability in host acceptance among Mexican populations may also give greater insight into the region of origin of the pest lineage.