Using functional responses to quantify notonectid predatory impacts across increasingly complex environments

Abstract Predation is a key biotic interaction that influences both the structure and functioning of ecosystems, and is relevant in the biological control context. Levels of habitat complexity in aquatic ecosystems are highly variable and can profoundly affect predator-prey interactions through the presence of prey refugia, which can in turn reduce predatory efficacy. Here, we use functional responses (FRs, resource use under different resource densities) to quantify the predatory impact of the notonectid Anisops debilis towards larvae of the mosquito Culex pipiens under a habitat complexity gradient. Anisops debilis displayed a potentially population-destabilising Type II FR towards larval C. pipiens prey across the habitat complexity gradient. Attack rates were highest in simple environments, however handling times were not significantly affected by habitat complexity. Maximum feeding rates of A. debilis towards C. pipiens larvae were thus robust to habitat complexity variations. Our results demonstrate the substantial predatory impacts of notonectids towards larval mosquito prey irrespective of habitat complexities, which may assist in the biological control of pests and vectors in aquatic systems.