A meta-analysis of herbivore effects on plant attractiveness to pollinators.

Abstract

Herbivores may directly or indirectly affect plant attractiveness to pollinators. Although several studies have reported on these effects, there is yet no general consensus on the strength and sign of such interactions or their contingency on herbivory features such as the plant tissue attacked. We performed a meta-analysis of studies testing for effects of herbivores on floral traits, plant attractiveness to pollinators, and plant reproductive success. We also assessed whether herbivore effects depended on the plant tissue attacked by herbivores and if real or simulated herbivory was used. We found an overall significant negative effect of herbivores on floral traits, plant attractiveness to pollinators, and plant reproductive success. These effects were, however, contingent on the plant tissue attacked and on whether real or simulated damage was used. Real floral and leaf, but not root, herbivores showed detrimental effects on floral traits and plant attractiveness to pollinators. In addition, real leaf, but not floral or root herbivory, lowered plant reproductive success. Contrastingly, simulated leaf and floral herbivory showed no effect on any of the response variables. These findings help move forward our understanding of the strength and directionality of herbivore effects on plant attractiveness to pollinators and their underlying mechanisms.