Impact of Climate Change on “Aphid - Natural Enemies” Relationship

While the effects of global atmospheric changes on vegetation and associated insect populations (bottom-up interactions) are increasingly studied, how these gases affect the interactions between insects and their natural enemies (top-down interactions) is less clear. As the efficacy of natural enemies is governed largely by behavioral mechanisms, changes in their prey-seeking behavior or the behavior of insect prey defenses can change the dynamics of insect populations.
The impact of increases in atmospheric carbon dioxide concentrations on aphid population dynamic is well documented. However, nothing about their chemical ecology is reported in the literature. Aphids are using many chemical signals to communicate with each other or with their environment. For example aphids produce an alarm pheromone to signal the presence of a natural enemy (such as a predator or a parasitoid) in the colony. Moreover, this pheromone is used by natural enemies as a kairomone to locate aphid prey, and is thus at the center of aphid – natural enemies interactions.
In this study, the impact of elevated CO2 concentration on the emission of the alarm pheromone in the aphid A. pisum is studied. Using a zNoseTM (Gas chromatograph enabling the fast analyze of the chemical composition of a sample), the kinetic of the EBF emission in real-time is set up for a single individual predated by a coccinellid predator Harmonia axyridis Pallas. This experimentation is done both for aphids reared under ambient atmospheric conditions and for individuals reared under elevated CO2 concentrations. We present the differences in terms of emission dynamic and discuss the potential of these results in terms of biological control.