Supplementary Material 9 - Code from Heightened condition dependence of the sexual transcriptome as a function of genetic quality in Drosophila melanogaster head tissue

Theory suggests sexual traits should show heightened condition dependent expression. This prediction has been tested extensively in experiments where condition has been manipulated through environmental quality. Condition dependence as a function of genetic quality has, however, only rarely been addressed, despite its central importance in evolutionary theory. To address the effect of genetic quality on expression of sexual and non-sexual traits, we here compare gene expression in Drosophila melanogaster head tissue between flies with intact genomes (high condition) and flies carrying a major deleterious mutation (low condition). We find that sex-biased genes show heightened condition dependent expression in both sexes, and that expression in low condition males and females regresses towards a more similar expression profile. As predicted, sex-biased expression was more sensitive to condition in males compared to females, but surprisingly female-biased, rather than male-biased, genes show the higher sensitivity to condition in both sexes. Our results thus support the fundamental predictions of the theory of condition dependence when condition is a function of genetic quality.