Polyandry in the wild: temporal changes in female mating frequency and sperm competition intensity in natural populations of the tettigoniid Requena verticalis

Empirical tests of sexual selection theory generally utilize model systems under laboratory settings, and extend conclusions to evolutionary processes occurring in nature. The biological significance of laboratory findings will depend largely on the mating rates of females and patterns of paternity in natural populations, information on which is generally lacking. Here we use microsatellite markers to provide rare estimates of female mating rates and patterns of parentage in a species of tettigoniid, Requena verticalis, which has been used extensively to test theory on the evolution of male parental investment and its influence on the direction of sexual selection. We found that although the number of males having a genetic representation in the female's sperm stores was higher for females collected late in the breeding season than those collected early in the season, overall the female mating rate was lower than that expected from laboratory observations. Analysis of parentage of offspring produced by females at the end of the breeding season revealed that all males represented in the sperm stores fathered offspring, although paternity was biased away from that expected from random sperm utilization. The data show that the complete first male sperm precedence documented in laboratory studies of this species does not persist in natural populations. Our data provide a solid underpinning for conclusions drawn from laboratory studies of this species.