In many species, including humans and Drosophila, symmetric individuals secure more mating’s, suggesting that bilateral symmetry signals quality of potential mates and is subjected to sexual selection. However, this idea remains controversial, largely because obtaining conclusive experimental evidence has been hindered by confounding effects arising from methods used to increase asymmetry in test subjects. Here, we show that altering gravity during development increases asymmetry in Drosophila melanogaster without detrimental effect on survival, growth and behaviour. Testing males with altered gravity-induced asymmetry in female mate choice assays revealed symmetry-based discrimination of males via auditory cues. Females similarly discriminated against males with genetically-induced asymmetry, suggesting that their preference for symmetry is not specific to altered gravity. By segmenting male courtship song into left and right wing-generated song-bouts, we detected asymmetry in courtship song of altered gravity males with asymmetric wings that experienced rejection. Females experimentally evolved in absence of mate choice lacked this preference for symmetry, suggesting that symmetry is maintained by sexual selection. Our data provide evidence for the role of symmetry in sexual selection and reveals how non-visual cues can flag mate asymmetry during courtship.

The dataset collection methods have been completely discribed in the related manuscript