Trade-offs of strategic sperm adjustments and their consequences under phenotype-environment mismatches in guppies
We used the guppy (Poecilia reticulata) to investigate how mismatches between anticipatory phenotypes and the social conditions subsequently experienced affect male reproductive success. Male guppies kept in visual contact with females increase their sperm production compared to female-deprived males, but simultaneously reduce their courtship rate. Using a paired experimental design, we manipulated male perceived mating opportunities by housing them in the presence (FP) or in the absence of females (FA). We then measured male mating and insemination success under two conditions: 1) female-biased sex ratio, matching expected FP cues, and 2) male-biased sex ratio, matching expected FA cues. Under female-biased sex ratio, mating and insemination success were not affected by previous exposure to females, although FP males experienced a lower risk of sperm depletion after several copulations. However, FP males showed a small, but significant reduction in their mating success under male-biased sex ratio, when directly competing with an FA male. Males showed significant repeatability in mating and insemination success within sex ratio context, suggesting that the costs of producing mismatched anticipatory ejaculate responses are probably low in this species.