Population Biology, Ecology, and Evolution Graduate Program, Emory University, Atlanta, GA, United States.
Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, United States.
Evolution. 2023 Jun 1;77(6):1468-1478. doi: 10.1093/evolut/qpad048.
Gene flow into populations can increase additive genetic variation and introduce novel beneficial alleles, thus facilitating adaptation. However, gene flow may also impede adaptation by disrupting beneficial genotypes, introducing deleterious alleles, or creating novel dominant negative interactions. While theory and fieldwork have provided insight into the effects of gene flow, direct experimental tests are rare. Here, we evaluated the effects of gene flow on adaptation in the nematode Caenorhabditis elegans during exposure to the bacterial parasite, Serratia marcescens. We evolved hosts against nonevolving parasites for 10 passages while controlling host gene flow and source population. We used source nematode populations with three different genetic backgrounds (one similar to the sink population and two different) and two evolutionary histories (previously adapted to S. marcescens or naive). We found that populations with gene flow exhibited greater increases in parasite resistance than those without gene flow. Additionally, gene flow from adapted populations resulted in greater increases in resistance than gene flow from naive populations, particularly with gene flow from novel genetic backgrounds. Overall, this work demonstrates that gene flow can facilitate adaptation and suggests that the genetic architecture and evolutionary history of source populations can alter the sink population's response to selection.
基因流入种群可以增加加性遗传变异，并引入新的有利等位基因，从而促进适应。然而，基因流动也可能通过破坏有利基因型、引入有害等位基因或产生新的显性负相互作用来阻碍适应。虽然理论和实地研究提供了对基因流动影响的深入了解，但直接的实验测试却很少。在这里，我们评估了在暴露于细菌寄生虫 S. marcescens 时，线虫 C. elegans 中的基因流动对适应的影响。我们在控制宿主基因流动和来源种群的情况下，对非进化寄生虫进行了 10 代的进化。我们使用了具有三种不同遗传背景（一种与汇种群相似，两种不同）和两种进化历史（先前适应于 S. marcescens 或原始）的线虫来源种群。我们发现，具有基因流动的种群对寄生虫的抗性增加幅度大于没有基因流动的种群。此外，来自适应性种群的基因流动比来自原始种群的基因流动导致更大的抗性增加，特别是来自新遗传背景的基因流动。总的来说，这项工作表明基因流动可以促进适应，并表明来源种群的遗传结构和进化历史可以改变汇种群对选择的反应。
