A mechanistic basis for genetic assimilation in natural fly populations.

Despite decades of research, the process of genetic assimilation—where traits become independent of environmental cues—has remained poorly understood. Our study investigates this phenomenon using the ectopic veins (EV) trait in Drosophila. Our combined genomic analyses reveal that EV assimilation occurs in both outbred and inbred populations and is driven by the selection of preexisting regulatory alleles. In particular, our results challenge the notion that stress-induced genetic or epigenetic changes are the primary drivers of trait assimilation. Instead, they highlight the role of selection on preexisting genetic variation, providing insights into the fundamental processes of genetic assimilation.