Constable George W A, Rogers Tim, McKane Alan J, Tarnita Corina E
Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544;
Department of Mathematical Sciences, University of Bath, Bath BA2 7AY, United Kingdom;
Proc Natl Acad Sci U S A. 2016 Aug 9;113(32):E4745-54. doi: 10.1073/pnas.1603693113. Epub 2016 Jul 22.
Deterministic evolutionary theory robustly predicts that populations displaying altruistic behaviors will be driven to extinction by mutant cheats that absorb common benefits but do not themselves contribute. Here we show that when demographic stochasticity is accounted for, selection can in fact act in the reverse direction to that predicted deterministically, instead favoring cooperative behaviors that appreciably increase the carrying capacity of the population. Populations that exist in larger numbers experience a selective advantage by being more stochastically robust to invasions than smaller populations, and this advantage can persist even in the presence of reproductive costs. We investigate this general effect in the specific context of public goods production and find conditions for stochastic selection reversal leading to the success of public good producers. This insight, developed here analytically, is missed by the deterministic analysis as well as by standard game theoretic models that enforce a fixed population size. The effect is found to be amplified by space; in this scenario we find that selection reversal occurs within biologically reasonable parameter regimes for microbial populations. Beyond the public good problem, we formulate a general mathematical framework for models that may exhibit stochastic selection reversal. In this context, we describe a stochastic analog to [Formula: see text] theory, by which small populations can evolve to higher densities in the absence of disturbance.
确定性进化理论有力地预测，表现出利他行为的种群将被突变的作弊者驱向灭绝，这些作弊者获取公共利益却不做出贡献。我们在此表明，当考虑到人口统计学随机性时，选择实际上可能朝着与确定性预测相反的方向起作用，反而有利于显著提高种群承载能力的合作行为。数量较多的种群比数量较少的种群在抵御入侵方面具有更强的随机稳健性，从而获得选择优势，而且即使存在繁殖成本，这种优势也可能持续存在。我们在公共物品生产的特定背景下研究这种普遍效应，并找到导致公共物品生产者成功的随机选择逆转条件。这里通过分析得出的这一见解，确定性分析以及强制固定种群规模的标准博弈论模型都未能发现。我们发现空间会放大这种效应；在此情形下，我们发现对于微生物种群，在生物学上合理的参数范围内会发生选择逆转。除了公共物品问题，我们为可能表现出随机选择逆转的模型制定了一个通用数学框架。在此背景下，我们描述了一种与[公式：见正文]理论类似的随机理论，通过该理论，小种群在没有干扰的情况下可以进化到更高的密度。
