Intraguild predation among exotic and native phytoseiids as influenced by pollen provisioning
Abstract: Amblydromalus limonicus and Transeius montdorensis are two exotic phytoseiid species recently imported in Europe as biological control agents of thrips in greenhouses. Both species are generalist predators and the climatic conditions in the Mediterranean do not exclude the possibility of their dispersion and successful establishment from greenhouse crops to orchards. Nevertheless, the ecological risks and the possible effects associated with exotic species on native phytoseiids have not been evaluated so far. The present work focused on the study of intraguild predation between A. limonicus and T. montdorensis and three native orchard inhabiting phytoseiid mites (i. e. Euseius stipulatus, E. finlandicus and Iphiseius degenerans). We show that both exotic species were superior intraguild predators to E. finlandicus and E. stipulatus but not I. degenerans. In addition, pollen provisioning reduced intraguild predation among the exotic and native phytoseiids but this effect was expressed in a species-specific manner. Nevertheless, this reduction was shown to be stronger for the Euseius compared to the exotic species or the native I. degenerans. Our study highlight the risk of releasing exotic biological control agents without previously assessing their interactions with native natural enemies of pests. Such interactions may be differentially affected by various factors among them the availability of alternative food sources.