CANCELLED - Drought modifies trophic interactions above and below ground

Background/Question/Methods

Climate change has the potential to disrupt trophic interactions between plants, primary and secondary consumers, which may lead to a change in the structure of terrestrial communities.  The present study examines the effects of drought on an above/below-ground system involving a Brassica plant, a generalist and a specialist aphid species (foliar herbivores), their parasitoids, and a dipteran species (root herbivore).  While a number of studies have examined the effects of above/below-ground interactions in multitrophic systems, there have been very few studies on the effects of abiotic factors on systems involving both above- and below-ground interactions. Experiments were conducted under controlled environment conditions. In the drought treatment, the quantity of water added per plant per week was 50 % of the full (control) water regime. We examined the effect of drought, with and without root herbivory, on the olfactory response of parasitoids (preference), plant volatile emissions, parasitism success (performance), and the effect of drought on root herbivory.

Results/Conclusions

Drought alone, or in combination with root herbivory, significantly altered parasitoid preference and performance. In the absence of root herbivory, the preference and performance of both parasitoid species was reduced significantly on drought-stressed plants compared with control plants. In the presence of root herbivory, the preference of both parasitoid species was reduced significantly on drought-stressed plants compared with control plants, however drought only significantly reduced performance in the generalist parasitoid species. Both drought stress and root herbivory reduced plant volatile emissions, which may explain why parasitoids preferred the control plants. Drought stress significantly reduced performance (pupal weight, percent emergence and adult longevity) of the root herbivore. The present work describes how drought can alter trophic interactions between root and foliar phytophages and parasitoids, and thus provides an insight into how the structure of terrestrial communities may be affected by drought.