Will top-down interactions be affacted by climate change?

Greenhouse gas emissions are rising since the beginning of the industrial era: atmospheric carbon dioxide now exceeds 400 ppm (30% increase since the mid-1800s) and tropospheric ozone has reached 40 ppb in industrialized areas. According to forecasting models, these concentrations are expected to double by the end of the 21st century. To date, impacts of elevated greenhouse gases have been extensively studied in plant-insect interactions, whereas interactions between herbivores and their natural enemies have been neglected. Because most interactions between herbivorous insects and their natural enemies are orchestrated by natural molecules produced as semiochemicals, we hypothesize that modification in atmospheric gas composition will alter chemical communication in insects, and affect the performance of natural enemies to locate their prey.
In this project, we shall attempt to analyze the effect of increase in greenhouse gas concentrations on insect communication, particularly in top-down interactions. The study model will consist in the interactions between the pea aphids (Acyrthosiphon pisum (Harris)) and their natural enemies Harmonia axyridis (Pallas) and Episyrphus balteatus (DeGeer). Under elevated CO2 and/or O3 concentrations, we will quantify the production of several aphid semiochemicals that are currently used as kairomones by natural enemies, including the aphid alarm pheromone E-β-farnesene and honeydew volatile compounds. Olfactometry assays will then be set up to examine the ability of natural enemies to locate their prey in the predicted atmospheric conditions of the end of the 21st century. Finally, using an Ecotron structure to be built in Gembloux Agro-Bio Tech, we will simulate a future ecosystem with the possibility to control additional biotic and abiotic parameters.