Variation in scale structure, structural colour and its genetic basis in two co-mimic species of Heliconius butterflies

Butterfly wings are adorned with colours that allow them to adapt to their environment in different ways. Heliconius erato and Heliconius melpomene are two species that display a striking variety of colours that in most cases converge due to Müllerian mimicry. The genetic basis of these patterns is well characterised. It shows simple Mendelian inheritance in most cases and it is parallel in the two species; homologous loci of large effect have been targeted by evolution during adaptation. In certain geographical regions these species also show convergence in blue wing iridescence; an angle dependent colour produced using nano-structures present in their scales. In contrast to pigmented patterns, little is known about the genetic basis of structural colour in Heliconius and other butterflies. In this thesis I characterise nano-structure variation relevant for structural colour production and explore its genetic basis. I describe its variation in natural and artificial populations, find loci controlling its variation and describe its putative genetic architecture. The genetic architecture of scale nano-structure and structural colour appears to be highly polygenic and divergent genetic mechanisms are used between species, unlike the case of pigmented wing patterns.