Key Laboratory of Inland Saline-Alkaline Aquaculture, Ministry of Agriculture and Rural Affairs, East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai, 200090, China.
Sci Rep. 2024 Aug 16;14(1):19020. doi: 10.1038/s41598-024-70007-3.
Reproductive investment decision is an integral part of life-history theory. Differential allocation hypothesis predicts that females should increase investment when mated to high-quality males, conversely, reproductive compensation hypothesis predicts that females should increase investment when mated to low-quality males. Empirical research dominantly focuses on polygamous species and rarely on serially monogamous species. So, the question remains: which hypothesis does serially monogamous species fit? And if it fits reproductive compensation hypothesis, do females only compensate once or continuously for multiple times when mating to low-quality males? Here, we used a serially monogamous fish, the lined seahorse (Hippocampus erectus), to investigate the reproductive investment pattern of females in relation to male quality (measured by sexual attractiveness). We found that females allocated more resources into eggs when they mated to less-sexually-attractive males, indicating the investment pattern of lined seahorse falls in with the prediction of reproductive compensation hypothesis. This finding may imply that the sex role of seahorses is reversed, and female is the side imposed on a greater sexual selection pressure. On this basis, we compared the investment difference of females in two consecutive breeding events when mated to less-sexually-attractive males. We found that females allocated less resources into eggs in the second breeding than in the first one. Females reduced their reproductive compensation in the second breeding, which may be attributed to the improvement in the quality (e.g., paternal care ability) of their mates after the first breeding, thus eliminating the need for them to invest more in the second breeding.
生殖投资决策是生活史理论的一个组成部分。差异分配假说预测，当雌性与高质量的雄性交配时，它们应该增加投资；相反，生殖补偿假说预测，当雌性与低质量的雄性交配时，它们应该增加投资。实证研究主要集中在多配偶物种上，很少关注连续单配偶物种。因此，问题仍然存在：连续单配偶物种适合哪种假说？如果它符合生殖补偿假说，那么雌性在与低质量的雄性交配时，是只补偿一次还是连续多次？在这里，我们使用一种连续单配偶的鱼类，线纹海马（Hippocampus erectus），来研究雌性在与雄性质量（通过性吸引力来衡量）相关的生殖投资模式。我们发现，当雌性与性吸引力较低的雄性交配时，它们会将更多的资源分配到卵子中，这表明线纹海马的投资模式符合生殖补偿假说的预测。这一发现可能意味着海马的性别角色是颠倒的，雌性是处于更大的性选择压力下的一方。在此基础上，我们比较了雌性在与性吸引力较低的雄性连续两次繁殖时的投资差异。我们发现，雌性在第二次繁殖中分配到卵子的资源较少。雌性在第二次繁殖中减少了生殖补偿，这可能是由于第一次繁殖后雄性伴侣的质量（如父性照顾能力）提高，从而使它们在第二次繁殖中不需要投入更多资源。
