Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, Massachusetts 02138 E-mail:
Evolution. 2012 Mar;66(3):637-650. doi: 10.1111/j.1558-5646.2011.01477.x. Epub 2011 Nov 2.
The persistence of extensive variation in nature seems to stand against the most general principle of evolution by natural selection: in antagonistic interactions, the stronger type is expected to replace the weaker. Game theory shows that, however, in contrast to this intuitive expectation for interactions between two players, strategic considerations on fitness maximization in repeated pairwise interactions between three players (truels) or more (N-person duels) lead to what can be dubbed "survival of the weakest": the weakest individual can have the highest fitness. A paradox arises: competitive skills cannot be improved by natural selection, unless we assume mutations with strong effects or unless we assume that interactions are exclusively between two individuals. The paradox disappears, however, with more realistic assumptions (a mixture of duels and truels; the attacked individual backfires; the contest can end without a winner; defensive and offensive skills are correlated; players not directly involved in the contest suffer collateral damage). An unexpected new result emerges: the weaker types can persist in a population in the absence of recurrent mutations, migration, and fluctuating selection. Game theory and the analysis of N-person duels, therefore, help understand one of the most enduring puzzles in evolutionary biology: the maintenance of variation under constant selection.
在对抗性相互作用中，较强的类型预计会取代较弱的类型。然而，博弈论表明，与人们对两个参与者之间相互作用的直观预期相反，在三个参与者（truels）或更多参与者（N 人决斗）之间的重复成对相互作用中，对适应性最大化的策略考虑会导致所谓的“弱者生存”：最弱的个体可以具有最高的适应性。一个悖论出现了：除非我们假设具有强大影响的突变，或者除非我们假设相互作用仅在两个个体之间发生，否则竞争技能不能通过自然选择得到改善。然而，随着更现实的假设（决斗和 truels 的混合；被攻击的个体反击；竞争可以没有赢家结束；防御和进攻技能相关；未直接参与竞争的参与者遭受附带损害），这个悖论消失了。一个意想不到的新结果出现了：在没有反复突变、迁移和波动选择的情况下，较弱的类型可以在种群中持续存在。因此，博弈论和 N 人决斗的分析有助于理解进化生物学中最持久的难题之一：在持续选择下保持变异。
