Leaf domatia and protection of a predatory mite Typhlodromus doreenae Schicha (Acari: Phytoseiidae) from drying humidity

Abstract

AbstractWhen plant characteristics influence interactions between herbivores and their natural enemies, mutualism can result between plants and the third trophic level. Leaf domatia, small hair tufts, pockets, or pits in the leaf surface, frequently shelter predaceous and fungivorous mites that may decrease the impact of plant herbivores and fungal pathogens. Benefits that accrue to sheltered mites are unclear. One hypothesis is that domatia protect mites from drying humidity they would otherwise experience on the leaf surface. This hypothesis was tested using laboratory microcosms with leaves of two plant species, Viburnum tinus (Caprifoliaceae) and Coprosma repens (Rubiaceae), and a native Australian phytoseiid mite, Typhlodromus doreenae. Domatia were either removed or retained on leaves and the distribution and performance of T. doreenae provided with pollen as a food source was assessed at four levels of relative humidity (30%, 50%, 70% and 98% RH). When domatia were available, most adults and offspring of T. doreenae were found there, irrespective of RH level or plant species. The presence of domatia increased retention of adult mites on leaves of C. repens but not V. tinus. Domatia of both plant species increased mite reproduction but only at RH >70% on C. repens and at 98% on V. tinus. These results indicate that T. doreenae benefits from domatia, but these benefits are not strongly related to drying humidity. Other hypotheses, including escape from predators, may better explain association of mites with leaf domatia. Irrespective of RH, this predatory mite did benefit from use of domatia for shelter and reproduction, supporting a key requirement for plant–mite mutualism.