The contribution of epigenetic variation to evolution in crows

Chromatin modifications provide a substrate for epigenetic variation with evolutionary potential. To quantify the contribution of this layer of variation to evolution we leveraged genome and methylome sequencing data from an incipient avian species: all-black carrion crows, grey-coated hooded crows and their hybrids. Combining controlled experimentation under common garden conditions and sampling of natural genetic variation across the hybrid zone we show that 5mC methylation variation was almost exclusively explained by genome properties and ontogenetic program of the organism. Evidence for an environmental contribution was minor, and all methylation variation of potential importance to speciation clustered in intergenic space within a genomic region of elevated genetic differentiation encoding the diagnostic color-contrast between taxa. We conclude that methylation variation may aid in phenotypic translation of genetic polymorphism, but provides little scope for an autonomous contribution to evolution in this system.