Evolutionary Interactions Between Plant Reproduction and Defense Against Herbivores

Coevolution is among the most important evolutionary processes that generate biological diversity. Plant pollinator interactions play a prominent role in the evolution of reproductive traits in flowering plants. Likewise, plant herbivore interactions select for myriad defenses that protect plants from damage. These mutualistic and antagonistic interactions, respectively, have traditionally been considered in isolation from one another. Here, we consider whether reproductive traits and antiherbivore defenses are interdependent as a result of pollinator- and herbivore-mediated selection. The evolution of floral traits, self-fertilization, and separate sexes frequently affects the expression and evolution of plant defenses. In turn, the evolution of defense can affect allocation to reproductive traits, and herbivores often impose strong selection directly on floral traits. Theory and empirical evidence suggest that herbivores can intluence the evolution of selling from outcrossing and potentially the evolution of separate sexes from combined sexes. We identify several areas in which future research is needed to increase our understanding of the evolutionary interplay between reproduction and defense in plants.