The Italian sparrow (Passer italiae) is a species which formed from the hybridization of the house sparrow (P. domesticus) and the Spanish sparrow (P. hispaniolensis). Furthermore, Italian sparrow populations on different islands in the Mediterranean sea have genomes which contain different proportions of the two parental genomes. Thus, we can use this natural experiment to study the formation of species, and how gene expression regulation evolves. In particular, Italian sparrows show transgressive gene expression, where gene expression in the hybrid is more extreme than in either parental species, which also differs among populations. This suggests that there has been perturbation in the regulation of gene expression regulation in the hybrids and that these perturbations differ among populations. My project will be assessing the contribution of changes in DNA methylation to this transgressive expression and how it differs among Italian sparrow populations. Therefore elucidating the molecular mechanisms regulating gene expression, how they are perturbed in hybrid species, and how said mechanisms contribute to evolutionary dynamics.