Am Nat. 2019 Mar;193(3):409-423. doi: 10.1086/701786. Epub 2019 Jan 24.
To survive unpredictable environmental change, many organisms adopt bet-hedging strategies that are initially costly but provide a long-term fitness benefit. The temporal extent of these deferred fitness benefits determines whether bet-hedging organisms can survive long enough to realize them. In this article, we examine a model of microbial bet hedging in which there are two paths to extinction: unpredictable environmental change and demographic stochasticity. In temporally correlated environments, these drivers of extinction select for different switching strategies. Rapid phenotype switching ensures survival in the face of unpredictable environmental change, while slower-switching organisms become extinct. However, when both switching strategies are present in the same population, then demographic stochasticity-enforced by a limited population size-leads to extinction of the faster-switching organism. As a result, we find a novel form of evolutionary suicide whereby selection in a fluctuating environment can favor bet-hedging strategies that ultimately increase the risk of extinction. Population structures with multiple subpopulations and dispersal can reduce the risk of extinction from unpredictable environmental change and shift the balance so as to facilitate the evolution of slower-switching organisms.
为了应对不可预测的环境变化，许多生物采用了避险策略，这些策略最初是有代价的，但能提供长期的适应度收益。这些延迟适应度收益的时间范围决定了避险生物是否有足够的时间来实现它们。在本文中，我们研究了一种微生物的避险模型，其中有两种灭绝途径：不可预测的环境变化和种群随机波动。在时间相关的环境中，这些灭绝驱动因素选择了不同的转换策略。快速表型转换确保了在面对不可预测的环境变化时的生存，而转换较慢的生物则灭绝。然而，当同一群体中存在两种转换策略时，由有限种群大小引起的种群随机波动导致快速转换生物灭绝。因此，我们发现了一种新的进化自杀形式，即波动环境中的选择可以有利于避险策略，而这些策略最终会增加灭绝的风险。具有多个亚群和扩散的种群结构可以降低不可预测的环境变化带来的灭绝风险，并改变平衡，从而促进转换较慢的生物的进化。
