Nonconsumptive predator-driven mortality (NCM), defined as prey mortality due to predation that does not result in prey consumption, is an underestimated component of predator-prey interactions with possible implications for population dynamics and ecosystem functioning. However, the biotic and abiotic factors influencing this mortality component remain largely unexplored, leaving a gap in our understanding of the impacts of environmental change on ecological communities. We investigated the effects of temperature, prey density, and predator diversity and density on NCM in an aquatic food web module composed of dragonfly larvae (Aeshna cyanea) and marbled crayfish (Procambarus fallax f. virginalis) preying on common carp (Cyprinus carpio) fry. We found that NCM increased with prey density and depended on the functional diversity and density of the predator community. Warming significantly reduced NCM only in the dragonfly larvae but the magnitude depended on dragonfly larvae density. Our results indicate that energy transfer across trophic levels is more efficient due to lower NCM in functionally diverse predator communities, at lower resource densities and at higher temperatures. This suggests that environmental changes such as climate warming and reduced resource availability could increase the efficiency of energy transfer in food webs only if functionally diverse predator communities are conserved.

University of South Bohemia Faculty of Science Department of Ecosystem Biology Branišovská 1760 370 05 České Budějovice Czech Republic Czech Academy of Sciences Biology Centre Institute of Entomology Laboratory of Aquatic Insects and Relict Ecosystems Branišovská 1160 31 370 05 České Budějovice Czech Republic

University of South Bohemia Faculty of Science Department of Ecosystem Biology Branišovská 1760 370 05 České Budějovice Czech Republic Czech Academy of Sciences Biology Centre Institute of Entomology Laboratory of Aquatic Insects and Relict Ecosystems Branišovská 1160 31 370 05 České Budějovice Czech Republic Unité Mixte de Recherche 5174 'Evolution et Diversité Biologique' Université de Toulouse 3 Institut de Recherche pour le Développement Centre National de la Recherche Scientifique École Nationale Supérieure de Formation de l'Enseignement Agricole 118 route de Narbonne F 31062 Toulouse France

University of South Bohemia in České Budějovice Faculty of Fishery and Protection of Waters South Bohemian Research Centre of Aquaculture and Biodiversity of Hydrocenoses Zátiší 728 2 389 25 Vodňany Czech Republic

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