Genetic divergence of the seminal signal-receptor system in houseflies: the footprints of sexually antagonistic coevolution?

To understand fully the significance of cryptic female choice, we need to f ocus on each of those post mating processes in females which create varianc e in fitness among males. Earlier studies have focused almost exclusively o n the proportion of a female's eggs fertilized by different males (sperm pr ecedence). Yet, variance in male postmating reproductive success may also a rise from differences in ability to stimulate female oviposition and to del ay female remating. Here, we present a series of reciprocal mating experime nts among genetically differentiated wild-type strains of the housefly Musc a domestica. We compared the effects of male and female genotype on oviposi tion and remating by females. The genotype of each sex affected both female oviposition and remating rates, demonstrating that the signal-receptor sys tem involved has indeed diverged among these strains. Further, there was a significant interaction between the effects of male and female genotype on oviposition rate. We discuss ways in which the pattern of such interactions provides insights into the coevolutionary mechanism involved. Females in o ur experiments generally exhibited the weakest, rather than the strongest, response to males with which they are coevolved. These results support the hypothesis that coevolution of male seminal signals and female receptors is sexually antagonistic.