a1 Cardiff School of Biosciences, Biomedical Sciences Building, Cardiff University, Museum Avenue, Cardiff CF10 3AX, UK
a2 Mountain Agriculture Research Unit, Institute of Ecology, University of Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria
a3 Warwick HRI, University of Warwick, Wellesbourne, Warwick, CV35 9EF, UK
Generalist predators and parasitoids are considered to be important regulators of aphids. The former not only feed on these pests, but might also consume parasitoids at all stages of development. This direct or coincidental interference affects the natural control of aphids, the scale of which is largely unknown, and it has rarely been examined under natural conditions. Here, molecular diagnostics were used to track trophic interactions in an aphid-parasitoid-generalist predator community during the build-up of a cereal aphid population. We found that generalist predators, principally carabid and staphylinid beetles as well as linyphiid spiders, had strong trophic links to both parasitoids and aphids. Remarkably, more than 50% of the parasitoid DNA detected in predators stems from direct predation on adult parasitoids. The data also suggest that coincidental intraguild predation is common too. Generalist predators, hence, disrupt parasitoid aphid control, although the levels at which the predators feed on pests and parasitoids seem to vary significantly between predator taxa. Our results suggest that taxon-specific trophic interactions between natural enemies need to be considered to obtain a more complete understanding of the route to effective conservation biological control.
(Accepted August 31 2011)
(Online publication October 10 2011)
p1 Current address: Plant and Invertebrate Ecology, Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK