The evolution of resistance to herbivory in Ipomoea purpurea. I. Attempts to detect selection

Phenotypic regression analysis revealed directional selection for all 5 characters (plant size and resistance to 4 types of herbivores) and indicated that plant size and resistance to corn earworm Heliothis zea damage were subject to stabilizing selection. Analysis using breeding values revealed directional selection only for plant size and resistance to corn earworms, while none of the characters examined indicated stabilizing or disruptive selection. Results suggest that intermediate levels of damage in the annual morning glory are, in general, not maintained by stabilizing selection. Rather, they may reflect either 1) a transient state that exists while directional selection pushes the population toward complete resistance (or, in one case, total absence of resistance) or 2) the evolution of susceptibility to damage by genetic drift. -from Authors

Duke Scholars

Author Mark D. Rausher Biology