Environmental sampling and culturing of 3 diatom species for evolutionary experiments.</p><p>To explore the transcriptional networks underlying phenotypic changes in Hinners et al. (2022), we analyzed the transcriptomes of diatom strains originally characterized in Argyle et al. 2021 and Hinners et al. 2022. Each strain was split into 6 replicate populations and maintained at full selection (1000+ cells per transfer) in the control environment (i.e. control populations) throughout the experiment. In another treatment, these populations were bottlenecked (only 5-9 cells transferred at a time) to relax natural selection and induce phenotypic divergence. This bottleneck was then followed by recovery through full selection (i.e. back-selected) by next transferring 1000 cells per transfer for 200-500 generations. Samples for RNA-Seq were taken at the end of this recovery phase for both the control populations and the back-selected populations.