Non-consumptive effects of a top predatory may improved aphid control on a top predator-intermediate predators - Aphid system

Abstract

Non-consumptive effects (NCEs) of predators are known to alter prey behaviour, morphology and physiology, ultimately influencing prey fitness. However, NCEs among multiple predator species and on shared prey in pest control have rarely been experimentally isolated. In systems with intraguild predation, intermediate predators (intraguild prey) may reduce prey consumption in the presence of top-predators; on the other hand, intermediate predators may benefit from non-consumptive effects of top-predators on prey (e.g., escape behaviour). I investigated the effects of perceived risk from a top predator (the presence of predator cues) on the interaction between intermediate predators and their prey. I also investigated how these interactions were affected by intermediate predator identity and initial prey density. My model system comprised the adult ladybird Adalia bipunctata (top predator), ladybird Adalia bipunctata larvae and the green lacewing Chrysoperla carnea (intermediate predators), and the pea aphid Acyrthosiphon pisum (prey). Intermediate predators reduced aphid density more strongly in the presence of the adult ladybird cues. Furthermore, the reduction of prey density depended on both the identity of the intermediate predator and initial prey density. The observed multiple predator facilitation was likely driven by non-consumptive effects on the top-predator on prey that rendered them more vulnerable to capture by the intermediate predator. In conclusion, the presence of predation risk may improve prey control by certain predator species. Further studies are required to test non-consumptive effects of different top predator species on intermediate predators in this system and in different multiple predator systems to better understand the role of non-consumptive effects on prey control.