TY - JOUR T1 - The genetic basis of structural colour variation in mimetic <em>Heliconius butterflies</em> JF - bioRxiv DO - 10.1101/2021.04.21.440746 SP - 2021.04.21.440746 AU - Melanie N. Brien AU - Juan Enciso Romero AU - Emma V. Curran AU - Andrew J. Parnell AU - Carlos Morochz AU - Patricio A. Salazar AU - Pasi Rastas AU - Thomas Zinn AU - Nicola J. Nadeau Y1 - 2021/01/01 UR - http://biorxiv.org/content/early/2021/04/22/2021.04.21.440746.abstract N2 - Structural colours, produced by the reflection of light from ultrastructures, have evolved multiple times in butterflies. Unlike pigmentary colours and patterns, little is known about the genetic basis of these colours. Reflective structures on wing-scale ridges are responsible for iridescent structural colour in many butterflies, including the Müllerian mimics Heliconius erato and Heliconius melpomene. Here we quantify aspects of scale ultrastructure variation and colour in crosses between iridescent and non-iridescent subspecies of both of these species and perform quantitative trait locus (QTL) mapping. We show that iridescent structural colour has a complex genetic basis in both species, with offspring from crosses having wide variation in blue colour (both hue and brightness) and scale structure measurements. We detect two different genomic regions in each species that explain modest amounts of this variation, with a sex-linked QTL in H. erato but not H. melpomene. We also find differences between species in the relationships between structure and colour. Our results suggest that these species have followed different evolutionary trajectories in their convergent evolution of similar structural colour. This study provides a starting point for determining the genetic basis of structural colouration more broadly.Competing Interest StatementThe authors have declared no competing interest. ER -