Data from: Differential allocation revisited: when should mate quality affect parental investment?

Differential allocation (DA) is the adaptive adjustment of reproductive investment (up or down) according to partner quality. A lack of theoretical treatments has led to some confusion in the interpretation of DA in the empirical literature. We present a formal framework for DA that highlights the nature of reproductive benefits versus costs for females mated to males of different quality. Contrary to popular belief, analytical and stochastic dynamic models both show that additive benefits of male quality on offspring fitness have no effect on optimal levels of female investment and thus cannot produce DA. Instead, if offspring fitness is affected multiplicatively by male quality, or male quality affects the female cost function, DA is expected because of changes in the marginal benefits or costs of extra investment. Additive male quality effects on the female cost function can cause a novel form of weak DA, because reduced costs can slightly favor current over future reproduction. Combinations of these distinct effects in more realistic model scenarios can explain various patterns of positive and negative DA reported for different species and mating systems. Our model therefore sheds new light on the diversity of empirical results by providing a strong conceptual framework for the differential allocation hypothesis.

差异化投入（Differential Allocation，DA）指依据配偶质量对繁殖投入进行适应性调整（上调或下调）。由于相关理论阐释的匮乏，实证研究文献中对DA的解读存在一定混淆。本文提出了一套针对DA的正式分析框架，着重阐明了与不同质量雄性交配的雌性个体，其繁殖收益与成本的本质差异。与主流认知相悖的是，解析模型与随机动态模型均证实，雄性质量对后代适合度的加性收益，并不会影响雌性繁殖投入的最优水平，因此无法催生DA。反之，若后代适合度受雄性质量以乘性方式影响，抑或雄性质量作用于雌性的成本函数，则额外繁殖投入的边际收益或成本会发生变化，从而可预期出现DA。此外，雄性质量对雌性成本函数的加性效应，可催生一种全新的弱DA模式：当成本降低时，雌性会略微倾向于当前繁殖而非未来繁殖。在更贴合自然实际的模型情境中，这些不同效应的组合，能够解释不同物种与交配系统中已报道的各类正向、负向DA模式。因此，本模型为差异化投入假说提供了坚实的概念框架，为解读多样化的实证研究结果提供了全新视角。