Males responding to sperm competition cues have higher fertilization success in a soldier fly

Sperm competition has been demonstrated to be an important force shaping male behavior in a number of species. For example, males may prolong copulation duration when they perceive sperm competition to be high. Although male behavioral responses to sperm competition have been shown in several species, their effects on reproductive success have rarely been demonstrated. In the soldier fly Merosargus cingulatus, males prolong copulations when sperm competition is high and when mating with more fecund females. Here, I tested the hypothesis that this behavioral response results in higher reproductive success for males. I exposed males to different simulated levels of sperm competition (high or low male density at the oviposition site) then introduced a female. I allowed the pair to mate and the female to oviposit. I determined the percentage of offspring sired by the male using amplified fragment length polymorphism profiles. Sperm competition did not affect clutch size, but it did affect fertilization success: males under higher simulated sperm competition increased copulation duration and fertilized a higher percentage of a female's egg clutch than did males under lower sperm competition.