Monday, December 10, 2007 - 8:17 AM

Inbreeding in horsenettle influences volatile production and the preference and performance of the tobacco hornworm (Manduca sexta)

Casey M. Delphia, cmd283@psu.edu1, Jason R. Rohr1, Andrew G. Stephenson2, Mark C. Mescher1, and Consuelo M. De Moraes1. (1) The Pennsylvania State University, Department of Entomology, 501 ASI Building, University Park, PA, (2) The Pennsylvania State University, Department of Biology, 208 Mueller Lab, University Park, PA

Self-fertilization is widespread in plants and often leads to a reduction in fitness through inbreeding depression. Though the effects of inbreeding are well-documented for many plant traits, researchers have only recently begun to explore the impacts of inbreeding on plant-insect interactions. Many of these interactions are mediated by plant volatiles, which serve as foraging cues for insect pollinators, herbivores, and natural enemies of herbivores. Few studies have documented variation in volatile production among individuals within plant populations, and the genetic and ecological factors affecting this variation are poorly understood. We examined variation in volatile production as a function of inbreeding and maternal lines in common horsenettle, Solanum carolinense L., a wild Solanaceous weed that exhibits self-incompatibility—a trait rarely found in weedy species which must frequently colonize new habitats. We also examined the effects of inbreeding on the preference and performance of the tobacco hornworm, Manduca sexta. Our data indicate that inbreeding decreases overall volatile production. Furthermore, caterpillars preferred inbred plants in choice tests and grew larger on inbred plants relative to outcrossed plants. However, the observed effects on both volatile production and caterpillar performance were highly variable across maternal lines, indicating the presence of genetic variation for inbreeding depression in this plant.

Species 1: Lepidoptera Sphingidae Manduca sexta (tobacco hornworm)
Species 2: Coleoptera Chrysomelidae Epitrix (flea beetles)
Species 3: Coleoptera Chrysomelidae Leptinotarsa juncta (false potato beetle)