Sexual Size Dimorphism in the Color Pattern Elements of Two Mimetic Heliconius Butterflies

Sexual dichromatism and sexual dimorphism of body size are reasonably well studied in butterflies. Sexual size dimorphism of color pattern elements, however, is much less explored. The object of this study is Heliconius, a genus of butterflies well known for the coevolution between mate color preferences and mimicry. Given the sexual role of wing coloration, we investigated the existence of sexual size dimorphism in the wing color elements of a mimetic pair—Heliconius erato phyllis Fabricius and Heliconius besckei Ménétriés—and analyzed the allometric patterns of these traits. Correlation between size of elements in the dorsal and ventral wing surfaces were also estimated. In both species, three out of four elements were larger in males, but the non-dimorphic element was not the same. With regard to the allometric patterns, our most important finding was that smaller males of one species have proportionally larger yellow bars. This is the first study specifically concerning quantitative sexual dimorphism in the coloration of this well-known genus of butterflies and it opens new prospects to investigate sex-related natural selection and sexual selection of color pattern elements.