A principal aim of the proposal work is to understand the evolution of interactions between a herbivorous insect and several of its host plants. Although it is generally accepted that insects evolve in response to selection pressures mediated by plants, the role of insects attack as a cause of plant evolution is controversial. The P.I.'s propose to initiate a preliminary investigation of this role, using the butterfly Euphydryas editha, in which geographical variation of diet is already well documented. Studies of interpopulation variation of plant acceptability will quantify the contribution of plant variation to the observed geographical variation of insect diet. Correlations between attack rates and acceptability may suggest hypotheses about the nature and extent of plant evolutionary responses to insect attack. Within a plant population that shows variation of acceptability the investigators will estimate the correlation between acceptability and fitness in the presence and absence of insects. If there studies are successful, an experiment that simulates the evolutionary effects of insect attack by applying artificial selection to plant acceptability will be attempted.
