Little is empirically known about the contribution of mutations to fitness in natural environments. However, Fisher's Geometric Model (FGM) provides a conceptual foundation to consider the influence of the environment on mutational effects. To quantify mutational properties in the field, we established eight sets of MA lines (7-10 generations) derived from eight founders collected from natural populations of Arabidopsis thaliana from French and Swedish sites, representing the range margins of the species in Europe. We reciprocally planted the MA lines and their founders at French and Swedish sites, allowing us to test predictions of FGM under naturally occurring environmental conditions. The performance of the MA lines relative to each other and to their respective founders confirmed some and contradicted other predictions of the FGM: the contribution of mutation to fitness variance increased when the genotype was in an environment where its fitness was low, i.e., in the away environment, but mutations were more likely to be beneficial when the genotype was in its home environment. Consequently, environmental context plays a large role in the contribution of mutations to evolutionary process and local adaptation does not guarantee that a genotype is at or close to its optimum.

The attached data set represents all of the data represented in the Evolution article by Weng et al. Each row represents the performance of a replicate within either the Founder (P) or Mutation Accumulation Lines (MA) when planted in either France (F) or Sweden (S). Fitness = the product of 3 columns, if the plant survived (1= survived, 0 = did not survive to reproduce), then the number of fruits x the average fruit length (mm) x the predicted number of seed per fruit/length. Biomass is in mg. There are 8 different Founders with their respecitive MA lines. Four founders are from France and four from Sweden. Seedlings planted in the French and Swedish sites were planted in November and September 2015, respectively and harvested in May and June 2016, respectively. All data in the Excel spread sheet were collected at time of harvest.

MA lines with 10 or more replicates were used in the analyses. If an MA line had < 10 replicates at a site, then the line was not included in the analyses.