Fisher's general principle for sex allocation holds that population sex ratios are typically balanced because parents producing the rare sex are benefited and the rare sex alternates over time. In species that have temperature‐dependent sex determination (TSD), thermal reaction norms need to be adjusted at the population level to avoid extremely biased sex ratios and extinction. Extant species with TSD experienced drastic climatic changes in the geological past and must necessarily have mechanisms of adaptation. I propose here a conceptual framework to explain how TSD curves could be adjusted by means of natural selection, based on Fisher's equilibrium sex‐ratio principle. Through a process that alternatively favors mothers that tend to produce the rare sex under new temperatures, sex ratios eventually return toward a theoretical equilibrium. Prerequisites for this model are variability among mothers in the tendency to produce a particular sex at a given temperature (i.e., variability in the thermal reaction norm), inheritance of this trend, and higher fitness of the rare sex. This straightforward mechanism could facilitate thermal adaptation in species with TSD over multiple generations.

中文翻译：

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再平衡性别比：温度依赖性决定物种反应规范的调整


Fisher 的性别分配一般原则认为，群体性别比通常是平衡的，因为产生稀有性别的父母会受益，并且稀有性别会随着时间的推移而交替。在具有温度依赖性性别决定 （TSD） 的物种中，需要在种群水平上调整热反应规范，以避免性别比例极其偏倚和灭绝。现存的 TSD 物种在地质历史中经历了剧烈的气候变化，并且必须具有适应机制。我在这里提出了一个概念框架，以解释如何根据费舍尔均衡性别比原理通过自然选择来调整 TSD 曲线。通过一个交替有利于在新温度下倾向于产生罕见性别的母亲的过程，性别比最终回到理论上的平衡。该模型的先决条件是在给定温度下产生特定性别的母亲之间的可变性（即热反应范数的可变性）、这种趋势的遗传以及稀有性别的更高适应性。这种简单的机制可以促进 TSD 物种在多代中的热适应。