Temperature-mediated plasticity in egg and body size in egg size-selected lines of a butterfly

We examine genotype–environment interactions by using lines of the butterfly Bicyclus anynana artificially selected for differences in egg size in a full factorial design with two developmental and two oviposition temperatures. In accordance with the temperature–size rule, egg size and pupal mass increased by 4–5 and 8%, respectively, at lower temperatures. Genotype–environment interactions for both traits suggest that plasticity is largely independent of the trait value, and that there is potential for evolutionary change. These findings cast further doubt on the notion that temperature-mediated plasticity might be purely a physiological constraint.