Butterfly wings: the evolution of development of colour patterns

The diversity in colour patterns on butterfly wings provides great potentia l for understanding how developmental mechanisms may be modulated in the ev olution of adaptive traits. In particular, we discuss concentric eyespot pa tterns, which have been shown by surgical experiments to be formed in respo nse to signals from a central focus. Seasonal polyphenism shows how alterna te phenotypes can develop through environmental sensitivity mediated by ecd ysteroid hormones, whereas artificial selection and single gene mutants dem onstrate genetic variation influencing the number, shape, size, position, a nd colour composition of the eyespots. The expression patterns of the regul atory gene Distal-less reveal that these changes can arise at several diffe rent developmental stages, and the phenotypes indicate that some forms of c hanged pattern may occur much more readily than others. Further study of th e genes, of the developmental mechanisms, and of the functions of the patte rns will provide novel insights about the evolution of morphological divers ity. (C) 1999 John Wiley & Sons, Inc.