9509826 Berenbaum The interactions between the parsnip webworm, an introduced plant-feeding insect, and the wild parsnip, an introduced weed that serves as its principal host throughout its range, is one of very few natural systems in which estimates have been made of the ability of an insect to select for chemically based resistance in its hostplant. To date, attention in this system has focused on the role of furanocoumarins, insecticidal compounds produced by the plant, in conferring resistance against the insect. The focus of this proposal is to determine whether plant primary metabolites, which may serve as nutrients for insects, are under selection by insect herbivores. The hypothesis that plant nutritional quality can evolve in response to insect herbivory has remained effectively untested for almost two decades. This study is one of few to examine the consequences of variation in plant primary metabolites on insect resistance and as such can be used to evaluate that hypothesis and its implication for studies of plant/insect interactions. In addition to its importance to basic studies, this project has implications for the management of crop-consuming pest species. There is currently interest in developing novel mechanisms to reduce pest problems in agroecosystems and at the same time reduce chemical inputs to those systems. Because humans do not feed exclusively on a single plant species, as do many phytophagous insects, selective breeding for altered nutrient levels in plants may lead to reductions in insect damage in the absence of chemical inputs, with little or no adverse impacts on human consumers.
