Tolerance to deer herbivory and resistance to insect herbivores in the common evening primrose (Oenothera biennis)

The evolution of plant defence in response to herbivory will depend on the fitness effects of damage, availability of genetic variation, and potential ecological and genetic constraints on defence. Here we examine the potential for evolution of tolerance to deer herbivory in Oenothera biennis while simultaneously considering resistance to natural insect herbivores. We examined: i) the effects of deer damage on fitness; ii) the presence of genetic variation in tolerance and resistance; iii) selection on tolerance; iv) genetic correlations with resistance that could constrain evolution of tolerance; and v) plant traits that might predict defence. In a field experiment, we simulated deer damage occurring early and late in the season, recorded arthropod abundances, flowering phenology, and measured growth rate and lifetime reproduction. Our study showed that deer herbivory has a negative effect on fitness, with effects being more pronounced for late-season damage. Selection acted to increas...