Keystone nonconsumptive effects within a diverse predator community

Abstract

The number of prey killed by diverse predator communities is determined by complementarity and interference among predators, and by traits of particular predator species. However, it is less clear how predators' nonconsumptive effects (NCEs) scale with increasing predator biodiversity. We examined NCEs exerted on Culex mosquitoes by a diverse community of aquatic predators. In the field, mosquito larvae co‐occurred with differing densities and species compositions of mesopredator insects; top predator dragonfly naiads were present in roughly half of surveyed water bodies. We reproduced these predator community features in artificial ponds, exposing mosquito larvae to predator cues and measuring resulting effects on mosquito traits throughout development. Nonconsumptive effects of various combinations of mesopredator species reduced the survival of mosquito larvae to pupation, and reduced the size and longevity of adult mosquitoes that later emerged from the water. Intriguingly, adding single dragonfly naiads to ponds restored survivorship of larval mosquitoes to levels seen in the absence of predators, and further decreased adult mosquito longevity compared with mosquitoes emerging from mesopredator treatments. Behavioral observations revealed that mosquito larvae regularly deployed “diving” escape behavior in the presence of the mesopredators, but not when a dragonfly naiad was also present. This suggests that dragonflies may have relaxed NCEs of the mesopredators by causing mosquitoes to abandon energetically costly diving. Our study demonstrates that adding one individual of a functionally unique species can substantially alter community‐wide NCEs of predators on prey. For pathogen vectors like mosquitoes, this could in turn influence disease dynamics.

Effects of predator cues carry over from egg and larval stage to adult life-history traits in a damselfly

“…We found that indirect non-consumptive effects of fish cues decreased survival to emergence and the development time to emergence in the damselfly. These results correspond with those from previous studies (Tseng 2003, Hellmann et al 2011, McCauley et al 2011, Meadows et al 2017 and, thus, further confirm that indirect non-consumptive effects are present in many animals with complex life cycles (Benard 2004). The novelty of our experiment was that we looked across 3 developmental stages: eggs, larvae, and adults.…”

Re‐emphasizing mechanism in the community ecology of disease

“…Predators of vectors can prevent pathogen establishment in naïve host populations, and the introduction of a vector predator into a host-vector-parasite system at equilibrium can extirpate pathogens through vector population regulation (Moore, Borer, & Hosseini, 2009). Non-consumptive effects of predators on the vector Culex can also decrease vector density by decreasing survival to pupation, adult size, and longevity (Meadows, Owen, & Snyder, 2017).…”

Bugs scaring bugs: enemy‐risk effects in biological control systems

“…Alternatively, even when defensive responses appear to conflict, the presence of multiple predators may sometimes improve prey survival. For example, Meadows et al (2017) showed that Culex mosquito larvae respond to a complex of mesopredators by diving towards the bottom of water bodies; however, in the presence of top predators, dragonfly larvae, which forage lower in the water column, diving responses by Culex are suppressed. Because the diving behaviour is costly, suppression of this response doubled the survival of larval mosquitoes to pupation.…”