2023

Kronholm, Ilkka

Evolution by natural selection requires that differences among individuals are heritable to some degree. However, evolutionary theory is not dependent on a particular mechanism of inheritance. Epigenetic changes, such as DNA methylation and particular histone modifications, can be inherited but their properties can differ from ordinary genetic mutations. Mutational supply, stability, and the distribution of phenotypic effects can be different for epigenetic mutations. Given these different properties, spontaneous epigenetic changes can alter evolutionary dynamics. Evolutionary models suggest that adaptation with epigenetic variation proceeds in two phases: adaptation happens initially via epigenetic changes, and in the second phase those epigenetic changes are replaced by genetic mutations. There is now some experimental evidence that suggests epigenetic variation can speed up adaptation this way. Moreover, plastic responses that are transmitted to the next generation via epigenetic changes can evolve in certain types of fluctuating environments and can affect subsequent adaptation to new a environment. While it is now clear that certain epigenetic changes can be inherited and can affect adaptation, many open questions remain concerning the importance of epigenetic changes in evolution.