Metabolic resource allocation vs. mating attractiveness: Adaptive pressures on the "alba" polymorphism of Colias butterflies.

The sex-limited "alba" genetic polymorphism in wing color of Colias butterflies has been studied with respect to potential selective pressures on this locus. Alba female pupae, carrying at least one dominant A allele, redirect resources, used by aa pupae for pigmentation, to other metabolic ends. Associated with this reallocation, alba, A-, female adults eclose earlier, retain more larva-derived resources in their fat bodies for somatic maintenance and for reproduction, and, in some conditions, mature their eggs faster than do aa females. Alba females are also less attractive to males than are aa females and mate less frequently. Evolutionary implications of these results are discussed.