Plants trap pollen to feed predatory arthropods as an indirect resistance against herbivory

Abstract

Plants commonly employ indirect resistance to reduce herbivory by provisioning predatory arthropod populations with additional resources. Numerous predatory arthropods consume pollen that is entrapped on dense, wooly trichomes of plants. Over two seasons, we supplemented pollen on the wooly leaves of turkey mullein, Croton setiger, in natural populations to determine if pollen entrapped on leaves supplements predatory arthropods and reduces herbivore populations and damage to the plant. Pollen supplementation increased the abundance of predatory spiders in both years and omnivorous Orius bugs in 1yr but had no effect on predatory hemipterans. Pollen supplementation reduced the abundance of herbivorous fleahoppers. Pollen supplementation decreased the amount of leaf damage experienced by plants over the season, suggesting that pollen entrapment may act as an indirect resistance. While C. setiger plants have little control over the amount of pollen on their surfaces, pollen adds to the diet of predatory arthropods that reduce herbivory, thus attraction of predators may be an adaptive benefit of leaf structures such as wooly trichomes that entrap pollen.