9423997 Chew This research will provide basic information on the evolution of plant-insect relationships, using a model system of cabbage butterflies and Brassica plants. The different sensitivities of geographic subspecies of a butterfly to chemicals in potential hostplants will be examined to explain patterns of plant use. Also, differences between and within populations of butterflies will be studied to document the genetic variability in a given insect species. The chemical compounds responsible for acceptance or rejection of specific plants will be identified. Bioassays for effects on egg-laying, larval feeding and growth of the insects will be used to isolate the active compounds, and the extent to which taste or toxicity are involved will be determined. The results are expected to provide an integrated picture of the interactions between plant chemistry and insect responses at different insect and plant life stages and with changing resource availability. This research is expected to result in the identification of natural chemical compounds that defend plants against insects. Information on the most vulnerable stage of the insects will be obtained, so that an accurate picture of plant escape from herbivory may result. Since the project involves both native and introduced insects and plants, predictions about the development of new plant-insect associations my be possible. The research may also determine the likelihood that a native insect can adapt to the different chemistry of an aggressively spreading naturalized plant.
