FRIBIO-Biologi og biomedisin

The genetic basis of phenotypic change and adaptation is one of the major outstanding problems in evolutionary biology. Until recently it has been difficult to identify the genes involved, particularly in wild populations. The biochemical pathways of mela nin-based fur and plumage pigmentation are evolutionary conserved, thus being a promising model system with several candidate genes available to study the molecular basis of adaptation. One of these genes, the melanocortin-1-receptor gene (MC1R), has rece ntly been shown to be associated with intraspecific melanism in several mammal and bird species. Our recent discovery of the MC1R-based melanism in arctic skuas (Stercorarius parasiticus) has generated an exceptional opportunity to resolve the evolutionar y history of plumage variation to a degree not achieved before in any group of birds. Skuas (Stercorariidae) comprise several species with conspicuous ventral plumage polymorphism and monomorphic congeners. Earlier studies on their evolutionary history ha ve produced surprising, and often contradictory results. Based on the MC1R-based melanism in arctic skuas, we wish to continue our study on evolutionary genetics in the entire skua family by employing a combination of multilocus phylogenetic analyses usi ng neutral markers with analyses of the evolutionary history of the pigmentation gene(s) involved in phenotypic change. In case the MC1R is not associated with plumage pigmentation in all species we will test further candidate genes potentially involved i n melanism. Furthermore, the identification of the genetic basis of melanism enables the use of population genetic data to investigate whether there is an adaptive advantage of melanism in polymorphic species, which will be investigated in the arctic skua . The forthcoming results will be of general importance for understanding the genetic basis of adaptation in both birds and vertebrates, and will advance the ongoing discussion of the skuas' evolutionary history.