Fig. 5

Eyespots and spots are non-homologous traits that might share homology at the level of GRNs. Both pierid spots and nymphalid eyespots may share common developmental modules. The core set of genes, as represented by the red bar, identified as common to both wing patterns may be a representation of an ancient ‘melanism’ module that was used in both patterns to produce melanin pigments or an ancient ‘wing patterning’ module that has been used repeatedly amongst butterfly species to organise the formation of patterns on the wing. However, more work needs to be done to validate the role(s) of this core set of genes in wing pattern development. Also, the function of gene enhancers common to these two non-homologous traits would also have to be studied to confirm that homology exists at the level of GRNs. The modular network shown here is a hypothetical example of how some of the genes identified as upregulated in both spot and eyespot wing tissues may be arranged within a network