Mutations can alter the short-term fitness of an organism, as well as the rates and benefits of future mutations. While numerous examples of these evolvability modifiers have been observed in rapidly adapting microbial populations, existing theory struggles to predict when they will be favoured by natural selection. Here we develop a mathematical framework for predicting the fates of genetic variants that modify the rates and benefits of future mutations in linked genomic regions. We derive analytical expressions showing how the fixation probabilities of these variants depend on the size of the population and the diversity of competing mutations. We find that competition between linked mutations can dramatically enhance selection for modifiers that increase the benefits of future mutations, even when they impose a strong direct cost on fitness. However, we also find that modest direct benefits can be sufficient to drive evolutionary dead ends to fixation. Our results suggest that subtle differences in evolvability could play an important role in shaping the long-term success of genetic variants in rapidly evolving microbial populations.

突变可以改变生物体的短期适应性，以及未来突变的速度和益处。虽然在快速适应的微生物种群中观察到了这些进化性修饰剂的许多例子，但现有理论难以预测它们何时会受到自然选择的青睐。在这里，我们开发了一个数学框架，用于预测遗传变异的命运，这些变异改变了相关基因组区域中未来突变的发生率和益处。我们推导出分析表达式，显示这些变体的固定概率如何取决于种群的大小和竞争突变的多样性。我们发现，连锁突变之间的竞争可以显着增强对修饰物的选择，从而增加未来突变的好处，即使它们对适应性施加了很大的直接成本。然而，我们也发现，适度的直接好处足以将进化的死胡同推向固定。我们的结果表明，进化能力的细微差异可能在塑造快速进化的微生物种群中遗传变异的长期成功中发挥重要作用。