Document: AND-3-48-26

Host plant manipulation of arthropod communities: Acarodomatia mediate antagonistic interactions between beneficial mites.

NORTON, A.P.* and G.ENGLISH-LOEB

Cornell University NYSAES, Geneva, NY 14456 ¹

Abstract:
Antagonistic interactions between predaceous organisms can have profound effects on lower trophic levels. When predaceous taxa prey upon or compete with one another their prey may experience lower predation pressure and thus reach higher densities in the presence of both predators than in the presence of only one species. We have been investigating the role of acarodomatia (small tufts of hair on the underside of leaves that are associated with higher densities of several taxa of beneficial mites) in mediating interactions between beneficial mites and their host plants. Using a factorial design, we manipulated access to domatia and the presence of two species of beneficial mite on the wild grape Vitis riparia. Both mite species (the mycophagous Orthotydeus lambi and predaceous Amblyseius andersoni) utilize the domatia of wild grape. In the absence of domatia there was strong evidence for a negative interaction between these two mites: Both species were at lower densities when in the presence of the other mite than when alone. In contrast, when provided with access to domatia there was no evidence for an adverse effect of these mite species on each other. Thus host plant traits may reduce antagonistic interactions between beneficial taxa, thereby enhancing the overall level of predation on plant parasites.

Keywords: Tritrophic interactions, Mutualism, Predator-predator interference

This abstract is being presented at: 10:15 AM in session:
Oral Session #44: Terrestrial Invertebrates: Foodwebs and Plant Responses.