Effects of urbanization on wild populations: searching for signals of selection in the genome of urban birds

Local adaptation is an ubiquitous phenomenon in nature and investigating cases of local adaptation can give us insight into both theoretical questions in evolutionary biology and practical issue as controlling of invasive species and managing of species facing anthropogenic global climate change. In this study, we investigated an event of local adaptation to urbanization in a Neotropical bird species, Coereba flaveola, describing the neutral genetic pattern resulting from urbanization, and addressing whether adaptive genetic divergence through local natural selection occurred in urban populations. Specifically, we investigate whether previously observed behavioral adaptation to urbanization results from genetic adaptation. To answer these questions, we implemented a genome-scan approach based on RADseq genomic data generated, using within-population selection analysis (to look for signatures of local selection across the genome), between-population analysis (looking for loci with differentiation between urban and rural populations higher than would be expected under neutrality) and genome-environment association (investigating the correlation between genotype frequency and urbanization variable). We uncovered over 150 thousand loci, among which 1928 were recovered as outliers, and 49 of them were unambiguously associated to biological processes possibly related to urban adaptation. These loci suggest urban individuals of Coereba flaveola underwent adaptation for visual acuity, higher activity and metabolism and more efficient immunological system. Moreover, fundamental genes underlying the morphological structure of the nervous system showed signatures of selection in urban individuals, suggesting behavioral adaptation may have a genetic basis.