Leaf Morphology and Predators: Effect of Leaf Domatia on the Abundance of Predatory Mites (Acari: Phytoseiidae)

Tritrophic-Ievel studies of predator–prey interactions on leaves have emphasized the role of plant secondary chemistry, but leaf morphology can also influence predation. We found that domatia, structures with mite-sized spaces in the vein axils of leaves on many woody angiosperms, often sheltered predatory mites (Phytoseiidae and Stigmaeidae). Leaves with domatia generally had much higher numbers of phytoseiid mites, especially their eggs, than those without domatia. This occurred within plant species, between congeners, and across unrelated species of rain forest trees and vines with and without domatia. When leaf domatia of a rain forest tree, Elaeocarpus reticulatus Smith, were blocked with a bitumen paint, numbers of phytoseiid mites per leaf were reduced to 24% of controls. These results show that morphological traits of plants can have a strong effect on the distribution and abundance of predators. Such predator enhancement may complement plant allelochemical defenses.