It is the unprecedented access to genome wide data that highlights the potential of current evolutionary studies and this proposal aims at exploiting this progress to analyze evolutionary processes in a well-established fish system of hybrid speciation. We study natural populations of freshwater fish referred to as sculpins (Cottus). In these we have identified species that have recently (<200 years) hybridized as a result of secondary contact through man-made canals between river systems. This gave rise to a new lineage with new adaptations that have allowed it to invade habitats that were not used by the parental species before. We are thus also dealing with evolutionary change that is associated with man-made ecological perturbations, the analysis of which is particularly timely. It is now possible to perform a near exhaustive search to identify genes and to study gene expression as a measure of evolutionary change in Cottus. A combination of genetic mapping experiments and screens for genotypic selection can reveal loci and functions as targets of selection in the adaptive evolution of invasive Cottus. This proposal specifically aims at identifying genomic traits such as copy number changes of coding sequences or changes in the gene regulatory architecture that have evolved as a direct consequence of hybridization and to explore their implication in adaptive evolution. The results will contribute to our understanding of the genetics of adaptation and the invasion of a new environment. With respect to hybrid zones and the evolution of new species, we will identify candidate genes and functions that can explain barriers to reproduction in the wild. Finally, we will be able to make significant progress with respect to the genetics associated with hybrid speciation.