The complex interplay of sex allocation and sexual selection

It is well recognised that sex allocation strategies can be influenced by sexual selection, when females adjust offspring sex ratios in response to their mates’ attractiveness. Yet the reciprocal influence of strategic sex allocation on processes of sexual selection has only recently been revealed. Recent theoretical work demonstrates that sex allocation weakens selection for female preferences, leading to the decline of male traits. However, these results have been derived assuming that females have perfect knowledge of mate attractiveness and precise control over cost-free allocation. Relaxing these assumptions highlights the importance of another feedback: that adaptive sex allocation must become difficult to maintain as traits and preferences decline. When sex allocation strategies erode not only traits and preferences but also their own selective advantage, predictions can no longer be expressed as a simple linear correlation between ornament exaggeration and adaptive sex allocation. Instead, strongest sex ratio biases may be found at intermediate trait levels.

学界已达成共识：当雌性依据配偶吸引力调整后代性别比例时，性选择可对性别分配策略产生调控作用。然而，策略性性别分配对性选择过程的反向调控作用，直至近年才得以揭示。近期的理论研究表明，性别分配会削弱对雌性择偶偏好的选择压力，进而导致雄性性状的衰退。但此类研究结论均基于以下假设：雌性可完全知晓配偶的吸引力，且能精准控制无成本的性别分配过程。放宽上述假设后，另一项反馈机制的重要性得以凸显：随着雄性性状与雌性偏好的衰退，适应性性别分配将愈发难以维持。当性别分配策略不仅会削弱雄性性状与雌性偏好，还会侵蚀自身的选择优势时，此前关于装饰性状夸张程度与适应性性别分配间呈简单线性相关的预测将不再成立。与之相反，最强的性别比例偏差或许会出现在性状处于中等水平的种群中。