Gene Behind Visual Mating Rituals in Heliconius Butterflies Uncovered

A particular gene plays a critical role in visual preference for mate choice between closely related Heliconius butterflies, according to a new study. The findings provide insight into how visually guided behaviors can be encoded within the genome. Many species use color and other visual cues to attract and recognize suitable mates. As such, visual preferences are important drivers of mate choice and sexual selection. However, while the genetics and evolution of the traits that serve as these cues – such as butterfly wing color – are increasingly understood, far less is known about the specific genetic mechanisms that underly the preference for these traits. Heliconius butterflies are well known for their diversity of bright wing patterns, which are used as mating cues. Although previous work has identified genomic regions controlling differences in male courtship behaviors between closely related Heliconius species, the exact genes involved remain unknown. Taking advantage of the mimicry relationships between two species of Heliconius (H. cydno, H. Melpomene, and H. timareta) that overlap geographically but display differences in both wing coloration and mate preference, Matteo Rossi and colleagues investigated how genetic variation for visual preferences has evolved in relation to color-pattern cues. Combining behavioral trials with genetic mapping, gene expression, and population genomic analyses, Rossi et al. found that two of these species – H. Melpomene and H. timareta – have evolved the same preference for red wing patterns. Rossi et al. found that a single gene, regucalcin1, was more highly expressed in H. cydno, a species that prefers white wings. CRISPR/Cas9 knock-out experiments of this gene altered male courting behavior towards conspecifics but did not affect other traits, including foraging behavior or wing color, suggesting its role in regulating visual preference among mates. "Examining the mechanisms by which regucalcin1 acts to regulate mate preference at the neuronal level could be a promising direction for future research," writes Adriana Briscoe in a related Perspective.