Insect herbivores modulate outcrossing rate in seed plants
Mating system;red queen;herbivory;natural enemies;evolutionary models
Evolution of plant mating system, such as selfing and outcrossing, is an intriguing question in vegetal biology, since that can suffer influence of several ecological factors. The Red Queen hypothesis suggests that biotic interactions parasite-host-like is the major factor driving the evolution and persistence of sexual reproduction in nature. Therefore, in light of this hypothesis, is expected that species under high pressures of parasites present high investment in sex, that in plants it can be measurement by the outcrossing rate. Although there are support for Red Queen for several groups of animals, in vegetal kingdom this hypothesis remains underexploited, especially using macroscale approaches. Here, our main objective was test if insect herbivores richness is effective in predict outcrossing rates in seed plants. For that, we fitted phylogenetic regressions using two independent datasets for these two variables and including some vegetative covariables: life span, growth form, specific leaf area and maximum height. The regressions were performed under two alternative evolutionary models: Brownian Motion and Ornstein-Uhlenbeck. We found, in both models, that plant species under higher pressure of insect herbivores richness had higher outcrossing rates. In the same line, we found that longer-lived plants tend to be higher outcrossing rates than short-lived. These results are in accordance with the expected by the Red Queen hypothesis, supporting the still scarce empirical framework of macroscale studies about the effect of natural enemies on evolution of mating system in seed plants.