An evolving landscape of sexual dimorphism at the molecular level in Drosophila

In most sexual taxa, large phenotypic differences in morphology and behavior exist between males and females.  Recent genomic evidence also supports a parallel phenomenon of sexual dimorphism existing at the transcriptome level.  Here, we characterize the evolution of sex-biased expression patterns across four species of Drosophila and describe both conservation and divegence in sexual dimorphism at the molecular level.  Genes that change expression patterns are preferentially found in sex-limited tissues and are, generally, less pleiotropic than those which remain conserved in their degree of sex-bias.  Gene ontological classes of these divergent sex-biased genes include chemosensory and cuticular proteins and indicate that sexual selection may be a strong yet cryptic evolutionary force in species divergence at the molecular level.