Genes with low-to-intermediate pleiotropy (1−Tau) drove most transcriptomic changes, specially contributing to the highest levels of parallelism. In contrast, early adaptation involved transient changes in more pleiotropic genes.

Most transcriptomic trajectories showed a rapid shift followed by a plateau—mirroring fitness changes and supporting the two phases of polygenic adaptation: directional and stabilizing.

A fast, concordant transcriptomic response revealed thousands of differentially expressed genes across generations.

Fecundity -a fitness component- increased rapidly over 7 generations, then plateaued suggesting the transition toward an equilibrium.