Butterfly eyespot patterns and how evolutionary tinkering yields diversity

Abstract

Eyespots are repeated elements in the wing pattern of butterflies. In the species-rich genus of Bicyclus, all eyespots are formed by the same developmental process. Artificial selection in B. anynana has explored how readily two of the eyespots can become different to each other. There is sufficient standing genetic and developmental variation in a single stock of this species for high flexibility in the responses for eyespot size; indeed selection over 25 generations in several directions of morphospace yielded phenotypes far beyond the variability found in the whole genus. In contrast, experiments on another eyespot trait, their colour composition, indicate that comparable flexibility occurs only along the axis of least resistance in which both eyespots change in the same direction. This result is reflected in both a clear difference in the developmental regulation of eyespot size and colour composition, and in the patterns of variability among species. Such research that integrates evolutionary genetics and Evo-Devo will eventually reveal how evolutionary tinkering occurs in both genetical and developmental terms, and will also explore the consequences of differences in evolvability for patterns of diversity.