Hox genes mediate the escalation of sexually antagonistic traits in water striders

Abstract

Sexual conflict occurs when traits favoured in one sex impose fitness costs on the other sex. In the case of sexual conflict over mating rate, the sexes often undergo antagonistic coevolution and escalation of traits that enhance females resistance to mating and traits that increase males persistence. How this escalation in sexually antagonistic traits is established during ontogeny remains unclear. In the water strider Rhagovelia antilleana, male persistence traits consist of sex combs in the forelegs and multiple rows of spines and a thick femur in the rearlegs. Female resistance trait consists of a prominent spike-like projection of the pronotum. RNAi knockdown against the Hox gene Sex Combs Reduced resulted in the reduction of both the sex comb in males and the pronotum projection in females. RNAi against the Hox gene Ultrabithorax resulted in the complete loss or reduction of all persistence traits in male rearlegs. These results demonstrate that Hox genes can mediate sex-specific escalation of antagonistic traits along the body axis of both sexes.