Greater costs of inducible behavioural defences at cooler temperatures in larvae of the mosquito, Aedes notoscriptus

Abstract

The evolutionary maintenance of inducible defences is governed by the costs and benefits of the defensive traits. The defensive traits should increase the chances of survival in the presence of predators, but be costly in their absence. The costs and benefits of inducible defensive traits can be influenced by environmental conditions, which subsequently affect the ability of prey to induce those defensive traits. We examine how temperature affects the costs of behavioural defences in larval mosquitoes, Aedes notoscriptus, which reduce activity in the presence of predator cues to limit detectability. The costs of reducing activity could either be exacerbated at warmer temperatures via increased metabolic demand, or ameliorated at warmer temperatures via accelerated development reducing exposure time. We compared life history traits of A. notoscriptus reared in control conditions to those exposed to predation cues as larvae at 18, 23 and 28 °C. Larvae reared in predation cues reduced activity, grew and developed slower and emerged later and smaller. While the reduction in activity increased with temperature, the negative effects on life history of A. notoscriptus were greatest at the coolest temperature. Our results show that the costs of inducible defences in A. notoscriptus are temperature dependent. This work suggests that variation in the thermal environment may have a strong influence on the dynamics of predator–prey interactions and the evolutionary maintenance of plasticity of defensive traits in natural populations.