Abstract
Lifehistory omnivory is common among parasitic wasps, where the larvae live on or in their insect host, but the adult wasps feed from floral or extra-floral nectar. Provision of floral subsidies may thus increase the local abundance or enhance the performance of natural enemies and improve biological control of pests. However, no studies have to date investigated the effect of floral subsidies in a four-trophic-level system. If floral resources, provided to enhance parasitism, improve the fitness of the parasitoids own natural enemies, then this would impact on the theory and practise of conservation biological control – and challenge some existing community-ecology theories. The aim of the proposed project is to study the effect of floral subsidies on the fitness of aphid parasitoids and hyperparasitoids and on insect community structure and biological control at different spatial scales. In the laboratory, we will compare the effect of floral subsidies on fitness between treatments where floral subsidies are or are not available. In field experiments, insects will be marked with rubidium when feeding from patches of flowers established within agricultural fields. We will then capture parasitoids and hyperparasitoids within and at different distances from the flower patches and analyse them for rubidium content. Parallel to the study of movement, we will assess how parasitism rate of both aphids and primary parasitoids varies with distance from the nectar source.
Sweden