Abstract
We will examine whether developmental mechanisms can bias the paths followed during evolutionary change in morphology. The different eyespots on a wing of a butterfly usually have a similar colour composition. In Bicyclus anynana, eyespots all have a white pupil, a black central disc and an outer gold ring. The same developmental process forms the different eyespots which represent serial developmental homologues. Patterns of gene expression (e.g. Spalt, engrailed and Distal-less) are consistent across the repeat units, and their expression domains are associated with the colour rings of the adult eyespots. Artificial selection applied to the colour of a single eyespot produced butterflies in which the gold ring is much broader (so-called 'gold' butterflies), or narrower ('black' butterflies) for all eyespots. This project will examine the degree to which the eyespots can be uncoupled from each other: can butterflies be 'built' in which one eyespot is 'gold' whilst another is 'black'? A selection experiment will determine the relative ease with which concerted or antagonistic patterns of change in colour can be achieved. It will thus examine the potential for (internal) evolutionary constraints in a system where we can explore both genetical and developmental mechanisms. Once divergent lines have been obtained, crosses will be made between them and a genome-wide QTL gene mapping analysis made together with association studies for candidate developmental genes (incl Sal, en, Dll). The pattern of change in response to selection within our model species will be compared to patterns of divergence observed across the 80 or so species in this genus. The development of eyespot colour differs from eyespot size. The results here will, therefore, be compared in detail with a recent study where eyespot size responded in a remarkably unconstrained manner in lines similarly selected in coupled and uncoupled directions. We will contrast the behaviour of the two eyespot features and make a direct comparison of the two sets of genes involved in selection responses. Thus, we will not only examine potentials for evolutionary change in different directions, but also the molecular nature of the evolutionarily relevant variation on which the changes in phenotype are based. The work will further integrate the fields of ecology and evolution whilst focussing on the roles of development and genetics in generating morphological variation.
Netherlands