Data from: Field measurements of genotype by environment interaction for fitness caused by spontaneous mutations in Arabidopsis thaliana

As the ultimate source of genetic diversity, spontaneous mutation is critical to the evolutionary process. The fitness effects of spontaneous mutations are almost always studied under controlled laboratory conditions rather than under the evolutionarily relevant conditions of the field. Of particular interest is the conditionality of new mutations - i.e., is a new mutation harmful regardless of the environment in which it is found? In other words, what is the extent of genotype-environment interaction for spontaneous mutations? We studied the fitness effects of 25 generations of accumulated spontaneous mutations in Arabidopsis thaliana in two geographically widely separated field environments, in Michigan and Virginia. At both sites, mean total fitness of MA lines exceeded that of the ancestors, contrary to the expected decrease in the mean due to new mutations but in accord with prior work on these MA lines. We observed genotype-environment interactions in the fitness effects of new mutations, such that the effects of mutations in Michigan were a poor predictor of their effects in Virginia and vice versa. In particular, mutational variance for fitness was much larger in Virginia compared to Michigan. This strong genotype-environment interaction would increase the amount of genetic variation maintained by mutation-selection balance.作为遗传多样性的终极来源，自发突变（spontaneous mutation）对进化过程至关重要。目前针对自发突变适合度效应（fitness effects）的研究，几乎均在受控实验室条件下开展，而非更契合进化过程的野外自然环境。尤其值得关注的是新发突变的条件依赖性（conditionality）——即新发突变的有害性是否不受其所处环境的影响？换言之，自发突变的基因型-环境互作（genotype-environment interaction）程度究竟如何？本研究以拟南芥（Arabidopsis thaliana）为研究材料，在地理分隔甚远的两个野外环境——密歇根州与弗吉尼亚州——中，探究了25代累积自发突变的适合度效应。在两个实验位点，突变积累系（mutation accumulation lines, MA）的平均总适合度均高于祖先株系，这与新发突变预期会导致平均适合度下降的理论预期相悖，但与此前针对该MA系的研究结果一致。我们观测到新发突变的适合度效应存在基因型-环境互作：即在密歇根州环境下的突变效应，无法有效预测其在弗吉尼亚州的效应，反之亦然。具体而言，弗吉尼亚州环境中的适合度突变方差（mutational variance）远高于密歇根州。这种强烈的基因型-环境互作，会提升突变-选择平衡（mutation-selection balance）所维持的遗传变异总量。