Ecological communities are increasingly modified by anthropogenic disturbances, including climate change and species loss or introduction. Previous research suggests that increased temperatures can modify predator-prey interactions by increasing predator feeding rates, and/or by hastening prey development rates through predator-vulnerable sizes/stages. Therefore, increasing temperatures can strengthen or weaken overall predation depending on the relative sensitivity of both predator and prey traits to temperature.
Predator diversity often increases the suppression of shared prey species. However, predator species can differ in their thermal sensitivity, and thus their ability to suppress stage-structured prey across a thermal gradient. Therefore, as temperatures rise, multi-predator assemblages may not demonstrate increased suppression. Here, we studied the effects of predator diversity on the suppression of a stage-structured prey across an ecologically relevant thermal gradient of 20-36°C. In a series of laboratory experiments, we quantified the temperature dependence of 1) development rates for the larval mosquito prey Aedes atropalpus and 2) short-term predation rates of Erythemis simplicicollis, Pachydiplax longipennis, and Pantala spp. dragonfly nymphs across a range of prey availability. We used a discrete time model uniting these experiments to predict how changes in predator diversity and temperature affect mosquito larval recruitment to adulthood.
Results/Conclusions
Temperature altered both prey development and predator feeding rates. Mosquito development was halved from 14 to 7 days across the temperature gradient. Prey consumption increased with temperature for all three predator species, however there was considerable variation in the temperature sensitivity of the functional response among species. Across the temperature range, temperature increased the maximum number of prey consumed by 111% for Erythemis, but only 47% for Pantala.
Model results highlight the importance of considering the response of both predator and prey traits to temperature. Prey suppression varied nonlinearly with temperature depending on predator diversity and the effects of temperature on predator consumption rates relative to prey development. For example, when three Erythemis were present in monoculture, prey suppression increased by 13% from 24-28°C. However, for Pantala and Pachydiplax monocultures, prey suppression instead decreased by 18% and 36% respectively across the same temperature range. When one predator of each species was present, prey suppression also decreased across this temperature range, but only by 13%. Therefore, when predator assemblages feature a more diverse set of responses to temperature, these types of predator-prey interactions may be buffered against climate change driven increases in both average temperatures and temperature variability.