BUTTERFLY WING PATTERNS - DEVELOPMENTAL MECHANISMS AND EVOLUTIONARY CHANGE

This paper integrates genetical studies of variation in the wing patte rns of Lepidoptera with experimental investigations of developmental m echanisms. Research on the tropical butterfly, Bicyclus anynana, is de scribed. This work includes artificial selection of lines with differe nt patterns of wing eyespots followed by grafting experiments on the l ines to examine the phenotypic and genetic differences in terms of dev elopmental mechanisms. The results are used to show how constraints on the evolution of this wing pattern may be related to the developmenta l organisation. The eyespot pattern can be envisaged as a set of devel opmental homologues; a common developmental mechanism is associated wi th a quantitative genetic system involving high genetic correlations. However, individual genes which influence only subsets of the eyespots , thus uncoupling the interdependence of the eyespots, may be importan t in evolutionary change. The postulated evolutionary constraints are illustrated with respect to differences in wing pattern found among ot her species of Bicyclus.