FLORAL NECTAR AFFECTS LONGEVITY OF THE APHID PARASITOID APHIDIUS ERVI AND ITS HYPERPARASITOID DENDROCERUS APHIDUM

摘要

In this study, the potential consequences of making a three- or four-trophic level system more complex by adding floral resources was studied in the laboratory for a range of plant nectar sources, the aphid parasitoid Aphidius ervi and its hyperparasitoid Dendrocerus aphidum. Parasitoids exposed to flowering buckwheat survived 4-5 times longer than those in the control (water only) and 3-4 times longer than those provided with phacelia, alyssum or coriander. Hyperarasitoids provided with buckwheat survived 5-6 times longer than those in the control and 3-5 times longer than those on the other flowering plants. Buckwheat, phacelia, alyssum and coriander can therefore enhance the 'fitness' of A. ervi without benefiting its aphid host, which does not feed on nectar. However, the 'fitness' of the hyperparasitoid may increase relatively more than that of the parasitoid, depending on the nectar source.