Warm developmental temperatures induce non‐adaptive plasticity in the intrasexually selected colouration of a dragonfly

Abstract

1. When the breeding environment fluctuates across generations, reproductive traits may evolve plasticity that optimises the balance between survival and mating success for the prevailing environment.2. For sexually selected colouration, this balance can depend on environmental temperatures. Accordingly, breeding colouration often co‐varies with temperature through space and time. However, whether such traits exhibit plasticity in response to environmental temperatures is poorly understood.3. In the present study, a dragonfly (Pachydiplax longipennis) was reared under ambient or experimentally warmed conditions and tested for plasticity in its intrasexually selected wing colouration. Although wing colouration improves male territorial success, these advantages are smaller under warmer conditions than cooler conditions. It was therefore predicted that males reared under the ambient thermal conditions of the study site (Cleveland, Ohio) would develop more wing colouration than those reared under experimentally warmed conditions.4. Contrary to this prediction, males reared in warm larval temperatures produced more wing colouration. Thus, although the secondary sexual colouration of this species displays some thermal plasticity, it does not appear to be adaptive relative to the known thermal variation of intrasexual selection in this population.5. Given that the environment often determines the strength and direction of sexual selection, future studies should consider the potential for non‐adaptive, and even maladaptive, developmental plasticity in the sexually selected traits of insects.