Pervasive G × E interactions shape adaptive trajectories and the exploration of the phenotypic space in artificial selection experiments.

This article investigates how genotype-by-environment (G × E) interactions and mutational variance shape adaptive trajectories and phenotypic space exploration in artificial selection experiments on maize flowering time. Using the Saclay divergent selection experiments (DSEs) conducted over 18 generations on two maize inbred lines, the study decomposes the selection response into contributions from standing genetic variation and de novo mutations, revealing two adaptive phases: an initial fixation of standing variants followed by sustained adaptation driven by incoming mutations. The authors demonstrate that selected mutations are enriched for favorable effects but also include a notable fraction of unfavorable mutations, likely due to antagonistic pleiotropy and environmental fluctuations affecting mutational effects across generations. Common garden experiments highlight pervasive G × E interactions that modulate the expression and detection of selection responses and pleiotropic effects, influencing correlated traits and the structure of genetic correlations. Overall, the findings emphasize the complex interplay of mutation, selection, pleiotropy, and environment in shaping long-term adaptive dynamics in selfing maize populations under strong selection and drift.