Epigenomics of local adaptation

Trees may be especially vulnerable to rapid environmental change because they cannot move and because they slowly develop to reproductive maturity. As a result, we are exploring, non-genetic mechanisms that may allow short-term response to environmental change. One intriguing potential mechanism is DNA (cytosine) methylation, an epigenetic mechanism. DNA methylation mutates quickly relative to DNA sequence, can be inherited across generations, varies among individuals and populations, and is thought to affect gene expression and thus phenotype. Thus, there is potential for methylation to be involved in evolutionary response to environmental change. We have found in oaks that CpG methylation variation is highly differentiated among populations and linked to putatively locally adaptive genomic regions (Platt et al. 2015 Mol Ecol). Furthermore, we have shown that CpG methylation can be especially strongly associated with climate on the landscape, suggesting that it may be involved in climate response (Gugger et al. 2016 Mol Ecol). Potential next steps are to evaluate the heritability of methylation in oaks, determine whether methylation acts independently or is simply controlled by the underlying genetics, and to what degree methylation variation arises randomly and is selected upon or arises by environmental induction. There remains considerable debate about the role of methylation in evolution and phenotypic plasticity.