Adaptive foraging behaviour in the presence of multiple prey types may mediate stability to predator-prey relationships. For biological control agents, the presence of alternative prey may thus reduce ecological impacts towards target organisms, presenting a key challenge to the derivation of agent efficacies. Quantifications of non-target effects are especially important for generalist biocontrol agents in their regulation of pests, vectors and invasive species. We examined the predatory impact of the notonectid Anisops debilis towards larvae of the vector mosquito complex Culex pipiens in the presence of varying densities of alternative daphniid prey. Experimentally, we quantified functional responses of A. debilis towards target mosquito prey under different background daphniid compositions, and also tested for prey switching propensities by the notonectid predator. Increasing background densities of daphniids significantly reduced the predatory impact of notonectids on mosquitoes, characterised by reductions in attack rates, lengthening of handling times and lessening of maximum feeding rates. Furthermore, notonectids displayed a significant selective preference in favour of daphniid prey over mosquitoes, irrespective of prey proportions in aquatic environments. Accordingly, notonectids did not display a prey switching pattern. We thus demonstrate that the presence of alternative prey can dampen predatory impacts of notonectids towards mosquitoes, as compared to more simplistic pairwise systems with singular prey choice. Accordingly, the effects of stabilising mechanisms, such as adaptive foraging, should be further integrated in biocontrol agent assessments.
Bibliographical noteFunding Information:
This study was funded by the Department for the Economy, Northern Ireland. We extend gratitude to Rhodes University for the provision of laboratory facilities. We acknowledge use of infrastructure and equipment provided by the South African Institute for Aquatic Biodiversity ( SAIAB ) Research Platform and the funding channelled through the National Research Foundation – SAIAB Institutional Support system . This study was partly funded by the National Research Foundation – South African Research Chairs Initiative of the Department of Science and Technology ( Inland Fisheries and Freshwater Ecology , Grant No. 110507 ).
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- Functional response
- Prey preference
- Prey switching
- Trophic interaction strength
ASJC Scopus subject areas
- Agronomy and Crop Science
- Insect Science