性别大小二态(SSD)是由男性和女性面临的选择压力和生活史权衡的差异引起的。SSD的近因可能涉及性别特异性死亡率,能量采集,和维护的能量消耗,生殖组织,和生殖行为。使用定量的,以个人为基础,北海平原参数化的生态遗传模型,我们探讨了这些机制对女性偏见的SSD的重要性,在这种情况下,雄性比雌性更小,并且比雌性更早达到性成熟(在鱼类中很常见,但也出现在节肢动物和哺乳动物中)。我们认为有两种机制可能是最终的原因:(a)男性对男性生殖行为的投资可能会演变为减少原本可用于体细胞生长的能量资源,(b)男性生殖投资的收益递减可能会演变为减少能量获取。总的来说,这两者都可以带来更小的男性体型。我们报告以下发现。首先,仅对男性生殖行为的更高投资不能解释北海plaiceSSD。这是因为这种更高的生殖投资需要更多的能量获取,这会导致成熟的延迟,导致男性偏见的SSD与观察结果相反。当考虑观察到的男性死亡率差异(较低)时,成熟被进一步推迟,导致更大的雄性。第二,仅男性生殖投资的收益递减就可以定性地解释北海plaiceSSD,即使定量匹配不完美。第三,这两种机制都可以调和,从而为,先前先进的Ghiselin-Reiss假说,根据这一点,如果较小的雄性的繁殖成功以雌性受精的争夺竞争为主导,它们就会进化,因为男性因此在生殖方面的投资会超过增长,可能意味着存活率较低,从而放松了男女之间的竞争。第四,通过结合两种机制,同时考虑男性在产卵季节产生的特定性别成本,可以实现与北海plaiceSSD的良好定量拟合。第五,由捕捞引起的演变很可能已经修改了北海plaiceSSD。
Sexual size dimorphism (SSD) is caused by differences in selection pressures and life-history trade-offs faced by males and females. Proximate causes of SSD may involve sex-specific mortality, energy acquisition, and energy expenditure for maintenance, reproductive tissues, and reproductive behavior. Using a quantitative, individual-based, eco-genetic model parameterized for North Sea plaice, we explore the importance of these mechanisms for female-biased SSD, under which males are smaller and reach sexual maturity earlier than females (common among fish, but also arising in arthropods and mammals). We consider two mechanisms potentially serving as ultimate causes: (a) Male investments in male reproductive behavior might evolve to detract energy resources that would otherwise be available for somatic growth, and (b) diminishing returns on male reproductive investments might evolve to reduce energy acquisition. In general, both of these can bring about smaller male body sizes. We report the following findings. First, higher investments in male reproductive behavior alone cannot explain the North Sea plaice SSD. This is because such higher reproductive investments require increased energy acquisition, which would cause a delay in maturation, leading to male-biased SSD contrary to observations. When accounting for the observed differential (lower) male mortality, maturation is postponed even further, leading to even larger males. Second, diminishing returns on male reproductive investments alone can qualitatively account for the North Sea plaice SSD, even though the quantitative match is imperfect. Third, both mechanisms can be reconciled with, and thus provide a mechanistic basis for, the previously advanced Ghiselin-Reiss hypothesis, according to which smaller males will evolve if their reproductive success is dominated by scramble competition for fertilizing females, as males would consequently invest more in reproduction than growth, potentially implying lower survival rates, and thus relaxing male-male competition. Fourth, a good quantitative fit with the North Sea plaice SSD is achieved by combining both mechanisms while accounting for sex-specific costs males incur during their spawning season. Fifth, evolution caused by fishing is likely to have modified the North Sea plaice SSD.