When the aggressiveness degree modifies IGP magnitude

In agroecosystems, intraguild predation (IGP) is an ecological interaction that can reduce the effectiveness of biological control programs. Since aggressiveness is correlated with a higher attack rate, it is suspected to influence IGP occurrence. To understand the consequences of increased aggressiveness on the IGP, we used two artificially selected lines of the generalist predator, Nabis americoferus (one aggressive and one docile). We hypothesized that IGP is positively correlated to aggressiveness. Individuals of N. americoferus were tested individually with an intraguild prey (IGPrey), Orius insidiosus, and in the absence or presence of an extraguild prey (XGPrey), third instars of Lygus lineolaris. Firstly, the attack rate of N. americoferus on O. insidiosus was recorded for 15 minutes and then the IGP after a period of 24 hours. We found that aggressive individuals performed a higher attack rate and IGP than docile ones even with the presence of XGPrey. Whereas docile individuals did not display a strong IGP in the absence of XGPrey, it increased significantly when they were introduced. Our results suggest that IGP is positively correlated to a high aggressiveness. Additionally, it seems that docile individuals are more prone to adjust their behavior according to environmental conditions. Finally, the implications of aggressiveness degree for the predator-prey dynamic is discussed.