Trade-offs of strategic sperm adjustments and their consequences under phenotype-environment mismatches in guppies

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.