Evolutionary divergence via sexual selection acting on females in a species with sex role reversal

There is much evidence that sexual selection drives the evolutionary divergence of male sexual traits, but little is known of females. Comparisons between neutral genetic divergence (F-ST) and phenotypic divergence (P-ST) among populations can reveal evolutionary responses to selection. In the bushcricket Kawanaphila nartee, changes in floral food availability cause sex roles to shift from competitive females and choosy males to choosy females and competitive males midway through the breeding season. Males call to attract females, and female auditory spiracle size is under sexual selection. We ask whether selection on females can drive an evolutionary divergence in auditory spiracle size among populations. We sampled 188 individuals from nine geographic locations and analysed 9478 neutral SNP loci and two phenotypic characters to estimate F-ST and P-ST respectively. We found that P-ST for female auditory spiracle size far exceeded the global F-ST, suggesting that female auditory spiracle size is subject to strong directional selection. We relate differences in phenotypic traits to differences in geological and floristic characteristics among the sites. Our data suggest that variation in sexual selection driven by variation in the floristic community on which this species feeds may contribute to the strength of directional selection acting on female K. nartee among populations. Together, these findings indicate that divergence among populations can be driven by sexual selection acting on females, even when that selection is temporary and circumscribed. Read the free Plain Language Summary for this article on the Journal blog.