Monday, December 10, 2007 - 9:05 AM

Can herbivory-induced host resistance maintain genetic variation in herbivores?: Quantitative genetics of tolerance to induction in the Colorado potato beetle (Leptinotarsa decemlineata)

Adam Ehmer,, State University of New York Stony Brook, Ecology and Evolution, 650 Life Sciences Building, Stony Brook, NY

Variation in herbivory-induced host resistance can create environmental heterogeneity for subsequent herbivores. This heterogeneity can maintain genetic variation in herbivore performance if there is variation in herbivore tolerance to host resistance or if tolerance carries a cost. Although evidence for genetic variation in herbivore performance traits is ample, there have been few experiments to address whether intraspecific variation in host resistance can maintain genetic variation in herbivores. Additive genetic variances, covariances, and correlations among herbivore performance traits in the Colorado potato beetle Leptinotarsa decemlineata were examined in a nested, paternal half-sibling design. Larvae were fed potato Solanum tuberosum that had been previously damaged by adult beetles or control plants that had not. Diets of wound-induced leaves reduced neonate weight gains and adult weights and slowed development times, but did not affect neonate consumption rates. Variation among maternal families was significant for many traits, but there was no evidence for additive genetic variation in any trait. Herbivore tolerance to host induction was examined in two ways, first by calculating the family-mean difference in a performance trait across diet treatments, and also by looking for a family-by-diet interaction for each trait. Herbivore tolerance varied among maternal families, but there was no evidence for additive genetic variation in tolerance to prior herbivory. Genetic correlations among performance traits were positive or not significantly different from zero, providing no evidence for genetically based tradeoffs in performance on the different diets. The importance of maternal effects variation in the evolution of herbivore tolerance is considered.

Species 1: Coleoptera Chrysomelidae Leptinotarsa decemlineata (Colorado potato beetle)