Detection of emergent multiple predator effects in a warming world.

Predicting the influence of predators on food webs remains challenging, particularly when multiple predator species share a common prey species. In these cases, interactive effects (termed 'emergent' multiple predator effects; MPEs) can cause predators to have stronger or weaker effects on their prey than would be expected independently. Many studies highlight the ubiquity of MPEs, however, recent work has shown that failure to account for nonlinear but fundamentally predictable drivers of predation rate (e.g. prey depletion, prey body size, temperature, etc.) can bias predictions used to detect MPEs. Here, we demonstrate the application of a framework addressing these biases, the generalized functional response (GFR) approach, using empirical data on the temperature-dependent predation of mosquito larvae (Aedes atropalpus) by a two-predator assemblage (a dragonfly nymph, Erythemis simplicicollis and a diving beetle, Laccophilus maculosus). We showed that increased temperature differentially enhanced predation in both predator species in isolation, and in accounting for this, we detected an emergent MPE in two-predator assemblages only at low temperatures (20°C). Our findings add to a growing body of research that suggests that the occurrence of MPEs may vary with temperature, while stressing the importance of accounting for nonlinear drivers of predation when testing for MPEs.