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.本研究以孔雀鱼（Poecilia reticulata）为实验对象，探究预期表型与后续遭遇的社会环境不匹配如何影响雄性繁殖成功率。与雌性隔离的雄性孔雀鱼相比，能与雌性产生视觉接触的雄性会提升精子生成量，但同时会降低求偶频率。本研究采用配对实验设计，通过将雄性孔雀鱼饲养于有雌性存在（FP）或无雌性存在（FA）的环境中，操控其感知到的交配机会。随后，我们在两种环境下测定雄性的交配成功率与授精成功率：1）雌性偏倚性比（匹配FP组预期的环境信号），2）雄性偏倚性比（匹配FA组预期的环境信号）。在雌性偏倚性比环境下，尽管FP组雄性在多次交配后出现精子耗竭的风险更低，但此前接触雌性的经历并未对其交配与授精成功率产生显著影响。然而，当在雄性偏倚性比环境下与FA组雄性直接竞争时，FP组雄性的交配成功率会出现小幅但显著的下降。雄性个体在相同性比环境下的交配与授精成功率具有显著的重复性，这表明本物种中产生不匹配的预期射精反应所需付出的代价可能较低。