The evolution of resistance to herbivory in Ipomoea purpurea. II. Natural selection by insects and costs of resistance

The annual morning glory exhibits genetic variation in resistance to 4 different types of insects. For 3 of these types, most of the genetic variation is additive. Removal of insect herbivores increased the number of seeds by 20% and eliminated additive genetic variation for seed number (fitness). This implies that herbivores impose selection on some trait(s) of their host plants. Coupled with selection for decreased damage by corn earworms Heliothis zea, as revealed by a negative additive genetic covariance between damage and fitness, this suggests that insect herbivores impose selection on resistance to corn earworms in I. purpurea. Cost-benefit arguments that attempt to predict the evolution of levels of resistance to herbivores are not applicable to I. purpurea. -from Authors

Duke Scholars

Author Mark D. Rausher Biology