The effects of prey patchiness, predator aggregation, and mutual interference on the functional response of Phytoseiulus persimilis feeding on Tetranychus urticae (Acari: Phytoseiidae, Tetranychidae).
The spatial distributions of two-spotted spider mites Tetranychus urticae and their natural enemy, the phytoseiid predator Phytoseiulus persimilis, were studied on six full-grown cucumber plants. Both mite species were very patchily distributed and P. persimilis tended to aggregate on leaves with abundant prey. The effects of non-homogenous distributions and degree of spatial overlap between prey and predators on the per capita predation rate were studied by means of a stage-specific predation model that averages the predation rates over all the local populations inhabiting the individual leaves. The empirical predation rates were compared with predictions assuming random predator search and/or an even distribution of prey. The analysis clearly shows that the ability of the predators to search non-randomly increases their predation rate. On the other hand, the prey may gain if it adopts a more even distribution when its density is low and a more patchy distribution when density increases. Mutual interference between searching predators reduces the predation rate, but the effect is negligible. The stage-specific functional response model was compared with two simpler models without explicit stage structure. Both unstructured models yielded predictions that were quite similar to those of the stage-structured model.
Nachman
Gösta
G
Department of Population Biology, Institute of Biology, University of Copenhagen, Universitetsparken 15, DK 2100, Ø Copenhagen, Denmark. gnachman@bi.ku.dk
D000818:Animals; D018553:Cucumis sativus / Q000469:parasitology*; D005247:Feeding Behavior; D008954:Models, Biological; D018515:Plant Leaves / Q000469:parasitology; D011235:Predatory Behavior; D040102:Tetranychidae / Q000254:growth & development / Q000502:physiology*