Genotype x environment interaction for male attractiveness in an acoustic moth:: evidence for plasticity and canalization

The lek paradox arises when choosy females deplete the genetic variance for male display traits from a population, yet substantial additive genetic variation (V-A) in male traits persists. Thus, the lek paradox can be more generally stated as one of the most fundamental evolutionary questions: What maintains genetic variation in natural populations? One solution to this problem may be found in the condition-dependent nature of many sexually selected traits. Genotype x environment (G x E) interactions can maintain V-A under conditions of environmental heterogeneity provided certain restrictions are met, although antagonistic pleiotropy has also been proposed as a mechanism. Here, we provide evidence for G x E interactions and against the role of antagonistic pleiotropy in the maintenance of V-A for sexually selected traits. Using inbred lines of the lesser waxmoth Achroia grisella, we measured V-A for song attractiveness, condition and development rate under different competitive environments and found that genotypes differed in their plasticity. We argue that variation persists in natural populations because G x E interactions prevent any one variant from producing the optimal phenotype across all environments.