Institute of Mathematics and Information Science, Baoji University of Arts and Sciences, Baoji, Shaanxi, China.
Computational Biology and Medical Ecology Lab, Theoretical and Experimental Ecology Lab, State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Science, Kunming, Yunnan, China.
Sci Rep. 2016 Dec 23;6:39807. doi: 10.1038/srep39807.
There are three sex ratio strategies (SRS) in nature-male-biased sex ratio, female-biased sex ratio and, equal sex ratio. It was R. A. Fisher who first explained why most species in nature display a sex ratio of ½. Consequent SRS theories such as Hamilton's local mate competition (LMC) and Clark's local resource competition (LRC) separately explained the observed deviations from the seemingly universal 1:1 ratio. However, to the best of our knowledge, there is not yet a unified theory that accounts for the mechanisms of the three SRS. Here, we introduce the price elasticity theory in economics to define sex ratio elasticity (SRE), and present an analytical model that derives three SRSs based on the following assumption: simultaneously existing competitions for both resources A and resources B influence the level of SRE in both sexes differently. Consequently, it is the difference (between two sexes) in the level of their sex ratio elasticity that leads to three different SRS. Our analytical results demonstrate that the elasticity-based model not only reveals a highly plausible mechanism that explains the evolution of SRS in nature, but also offers a novel framework for unifying two major classical theories (i.e., LMC &LRC) in the field of SRS research.
自然界中存在三种性别比例策略（SRS）——雄性偏向性比、雌性偏向性比和均等性比。正是 R.A. 费希尔首次解释了为什么自然界中的大多数物种表现出 1:2 的性别比例。随后的 SRS 理论，如汉密尔顿的局部配偶竞争（LMC）和克拉克的局部资源竞争（LRC），分别解释了与看似普遍的 1:1 比例的明显偏差。然而，据我们所知，目前还没有一个统一的理论可以解释这三种 SRS 的机制。在这里，我们引入经济学中的价格弹性理论来定义性别比例弹性（SRE），并提出一个分析模型，该模型基于以下假设推导出三种 SRS：同时存在对资源 A 和资源 B 的竞争，这两种竞争以不同的方式影响两性的 SRE 水平。因此，导致三种不同 SRS 的原因是两性之间的性别比例弹性水平存在差异。我们的分析结果表明，基于弹性的模型不仅揭示了一种极有可能的机制，解释了自然界中 SRS 的进化，而且为 SRS 研究领域中的两个主要经典理论（即 LMC 和 LRC）提供了一个新的统一框架。
