A genotype-phenotype-fitness map reveals local modularity and global pleiotropy of adaptation
Building a genotype to phenotype to fitness map of adaptation is a central goal in evolutionary biology. It is also notoriously difficult even when the adaptive mutations are known because it is hard to identify which phenotypes make these mutations adaptive. We solve this problem by first quantifying how the fitness of hundreds of adaptive mutants responds to subtle environmental shifts and then inferring the existence of fitness-relevant phenotypes implicit in these patterns of fitness variation. We find that a small number of phenotypes predicts the fitness of the adaptive mutations near their original glucose-limited evolution condition. Importantly, phenotypes that matter little to fitness at or near the evolution condition can matter strongly in distant environments. This suggests that adaptive mutants are locally modular - affecting a small number of phenotypes that matter to fitness in the environment where they evolve - yet globally pleiotropic - affecting many phenotypes that contribute to fitness in new environments.