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RESEARCH PRODUCT

Adaptive Evolution and Epigenetics

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Epigenetic changes, such as DNA methylation and certain histone modifications, can be inherited but in many cases they do not follow Mendelian inheritance patterns and their stability appears to be lower than for changes in DNA sequence. Adaptive evolution by natural selection requires that differences among individuals are heritable to some degree. Epigenetic changes can be incorporated into evolutionary theory, and given that properties of epigenetic variation are distinct from genetic variation, spontaneous epigenetic changes can affect evolutionary dynamics in interesting ways. In this chapter, I review the properties of epigenetic variation and how they relate to the main parameters of adaptive evolution. The main aspects in which epigenetic variation may differ from genetic variation include the supply and stability of epigenetic mutations, and the distribution of their effects on phenotype. Evolutionary modeling with realistic parameter values suggests that adaptation with epigenetic variation proceeds in two phases: first a population makes use of beneficial epigenetic mutations, and then in the second phase those epigenetic changes are eventually replaced by genetic mutations. However, evidence concerning the evolutionary importance of epigenetic variation is scarce and many open questions remain concerning mutation frequency and the extent to which epigenetic changes affect the phenotype.