Secondary trait loss is widespread and has profound consequences, from generating diversity to driving adaptation. Sexual trait loss is particularly common. Its genomic impact is challenging to reconstruct because most reversals occurred in the distant evolutionary past and must be inferred indirectly, and questions remain about the extent of disruption caused by pleiotropy, altered gene expression and loss of homeostasis. We tested the genomic signature of recent sexual signal loss in Hawaiian field crickets, Teleogryllus oceanicus. Song loss is controlled by a sex-linked Mendelian locus, flatwing, which feminises male wings by erasing sound-producing veins. This variant spread rapidly under pressure from an eavesdropping parasitoid fly. We sequenced, assembled and annotated the T. oceanicus genome, produced a high-density linkage map, and localised flatwing on the X chromosome. We characterised pleiotropic effects of flatwing, including changes in embryonic gene expression and alteration of another sexual signal, chemical pheromones. Song loss is associated with pleiotropy, hitchhiking and genome-wide regulatory disruption which feminises flatwing male pheromones. The footprint of recent adaptive trait loss illustrates R. A. Fisher's influential prediction that variants with large mutational effect sizes can invade genomes during the earliest stages of adaptation to extreme pressures, despite having severely disruptive genomic consequences.
When Does Sexual Signal Exploitation Lead to Signal Loss?
