Am Nat. 2019 Apr;193(4):503-513. doi: 10.1086/701799. Epub 2019 Feb 12.
Spatial structure is pervasive in the microbial world, yet we know little about how it influences the evolution of microbial populations. It is thought that spatial structure limits the scale of competitive interactions and protracts selective sweeps. This may allow microbial populations to simultaneously explore multiple evolutionary paths. But how structured a microbial population must be before this effect is realized is not known. We used empirical and simulation studies to explore the relationship between spatial structure and the maintenance of diversity. The degree of spatial structure experienced by Escherichia coli metapopulations was manipulated by varying the migration rate between its component subpopulations. Each subpopulation was inoculated with an equal number of two equally fit genotypes, and their frequencies in 12 subpopulations were determined during 150 generations of evolution. We observed that the frequency of the "loser" genotypes decreased exponentially as the migration rate between the subpopulations was increased and that higher frequencies of the loser genotypes were maintained in structured metapopulations. These results demonstrate that structured microbial populations can evolve along multiple evolutionary trajectories even when migration rates between the subpopulations are relatively high.
空间结构在微生物世界中普遍存在，但我们对其如何影响微生物种群的进化知之甚少。人们认为，空间结构限制了竞争相互作用的规模，并延长了选择的影响。这可能使微生物种群能够同时探索多种进化途径。但是，在实现这种效应之前，微生物种群必须具有多大的结构程度尚不清楚。我们使用实证和模拟研究来探索空间结构与多样性维持之间的关系。通过改变组成子种群之间的迁移率来操纵大肠杆菌复合种群所经历的空间结构程度。每个子种群都接种了相同数量的两种同等适应的基因型，并且在 150 代进化过程中确定了 12 个子种群中的频率。我们观察到，随着子种群之间的迁移率增加，“失败者”基因型的频率呈指数下降，并且在结构复杂的复合种群中，“失败者”基因型的频率保持较高。这些结果表明，即使子种群之间的迁移率相对较高，结构复杂的微生物种群也可以沿着多种进化轨迹进化。
