Experimental evidence for short term directional selection of epigenetic trait variation

Evolution by natural selection can occur when organisms harbor genetically inherited phenotypic variation, and phenotypic variants have differential fitness. Stable transgenerational epigenetic variation also exists for fitness-related traits and theory predicts that selection can act on this variation alone without a contribution of genetic variation. Here, we artificially selected for divergent biomass, rosette size, flowering time and height at first silique in experimental Arabidopsis thaliana populations harboring DNA methylation polymorphism in an identical genetic background. We found significant epi-allele frequency changes in response to selection. Our results show how selection rapidly changed population trait values and their epigenetic basis, over one generation of selection. Our results imply the role of the transgenerational epigenetic variation of populations as an additional source of short-term adaptive potential