Fig. 5.

Hierarchical clustering (HC) with multiscale bootstrap resampling of DM sites. HC of Bray−Curtis dissimilarities calculated from shared (n = 686) DM methylation levels in figure 2. Values at nodes are AUPs. The ancestral population is labeled in bold and the 7-year time points are labeled in green. Both the plastic (Amb-High) and adaptive (High) high-CO₂ conditions at the 4.5-year mark maintain segregation from the ancestral (Amb-ancestral) and ambient conditions as in plots in figure 2. Also consistent with plots in figure 2, two of the High-Amb replicates still cluster with the 4.5-year high-CO₂ conditions, whereas one replicate clusters with the ambient conditions. This demonstrates CO₂-responsive methylation levels to be returning to ancestral conditions once placed back into the ancestral environment. Upon adding *ambient and *High selected conditions at the 7-year time point (green), the *ambient replicates cluster with the Amb-ancestral and 4.5-year ambient conditions as expected, but the *High replicates also cluster with all ambient conditions, demonstrating the return of methylation levels originally triggered by high-CO₂ back to their ancestral ambient levels.