Artificial selection of reaction norms of wing pattern elements in Bicyclus anynana

Abstract

A novel use of selection was applied to the examination of the genetics of phenotypic plasticity. The approach provides a sensitive way of detecting genotype-environment (g x e) interactions and also allows the form of any interactions across an environmental gradient to be investigated through changes in the shapes of the reaction norms. The wing pattern of the butterfly B. anynana varies with season; eyespot size increases with development temperature. Selection lines to increase and to decrease eyespot size at 28°C were carried out. The effect of selection on the eyespot reaction norms with temperature was examined. Selection produced divergent reaction norms across the entire range of temperature in most eyespots. Significant g x e interactions were sometimes present but the degree of interaction was always relatively small. When present, the form of the interaction varied between the sexes. There was a high degree of genetic independence between the eyespots on the ventral and on the dorsal wing surfaces, except in the dorsal eyespot in the wing cell corresponding to the wing cell of the selected ventral wing surface eyespot. The significance of the results for the maintenance of genetic variation in B. anynana is considered. © The Genetical Society of Great Britain.