Genetic variability and phenotypic plasticity in pupal colour and its adaptive significance in the swallowtail butterfly papilio polyxenes

Abstract

Genetic variability and phenotypic plasticity have been suggested as mutually exclusive ways by which adaptation to environmental heterogeneity can be accomplished. The genetic and environmental components of variation in the darkness of brown pupae of the swallowtail butterfly Papilio polyxenes were investigated. Variation in darkness was found to be both genetic and environmental, with the darkness of the pupation site having a significant influence on the darkness of pupae, thus allowing for the production of cryptic brown pupae in nature. These results suggest that the evolution of phenotypic plasticity in a trait need not be to the exclusion of the maintenance of genetic variation in that trait. The results of field experiments show that cryptic pupae have a higher probability of escaping predation relative to noncryptic pupae. © The Genetical Society of Great Britain.