Although it is widely accepted that plant characters such as secondary chemistry, trichomes, and tough leaves have evolved primarily as defenses against herbivores, particularly insects, little direct evidence exists indicating that herbivorous insects impose natural selection on such resistance traits. the goal of the research proposed here is to determine whether insects exert natural selection on genetic variation for resistance in the morning glory, Ipomoea purpurea. The basic technique will be to examine how the experimental removal of four types of insects (the corn earworm, flea beetles, tortoise beetles, and generalist folivores) affects the magnitude of selection these insects impose on resistance to herbivory. In addition, whether resistance is due at least in part to tolerance or compensation (the ability of a plant to maintain a constant seed production despite herbivory) will be determined. Finally, the physiological and morphological characters that are responsible for resistance in insects in I. purpurea will be identified. Once these characters are known, whether and how insects exert selection on such characters will be examined.
