FIG. 28.16

What controls color pattern in butterfly wings?

BACKGROUND Butterfly wings commonly show a striking pattern of color, including circular features known as eyespots. Eyespots are adaptive, for example in deterring predation by birds.

HYPOTHESIS The expression of regulatory genes during wing development governs eyespot formation on wing surfaces.

EXPERIMENT Paul Brakefield and his colleagues mapped the expression of a regulatory gene called Distalless in developing butterfly wings. Distalless genes were fused to genes for green fluorescent protein (GFP), a protein that glows vivid green when illuminated under blue light. GFP is then expressed along with Distalless, allowing the spatial pattern of Distalless expression in developing wings to be visualized.

RESULTS The expression pattern of Distalless (on the left in each panel of the figure) in developing wings closely resembles the pattern of eyespots on the wing (on the right in each panel). The two patterns match for both wild-type (top left) and mutant butterfly wings.

CONCLUSION Regulatory genes play an important role in butterfly wing coloration, and mutations in these genes can account for differences in wing color patterns among species.

SOURCE Brakefield, P. M., et al. 1996. “Development, Plasticity and Evolution of Butterfly Eyespot Patterns.” Nature 384: 236–242.