Selection for Overcompensatory Plant Responses to Herbivory: A Mechanism for the Evolution of Plant-Herbivore Mutualism

Abstract

A mathematical model demonstrates that size-selective herbivory can drive the evolution of a mutualistic relationship between plants and herbivores. The fact that some monocarpic plants (e.g., Ipomopsis aggregata) can replace inflorescences lost to herbivory presents the opportunity for "bet hedging" within a single flowering season. When herbivory is sufficiently strong and size selective, the optimal plant strategy is to withhold a large proportion of its reproductive resources against the possibility that an initial investment will be consumed. Under these conditions, plant fitness is enhanced by herbivory, and selection should favor plant traits that increase the probability of being eaten.