Abstracts (first author)
Adaptive divergence in two coexisting stickleback species
Natural populations are at least partially adapted to local environmental conditions. The level of adaptation is promoted by divergent selection on ecologically relevant traits, but hampered by gene flow. The relative strength of both forces depends on genomic architecture as well as dispersal abilities, both of which might differ between species. In this study, we tested for divergent selection and gene flow in two coexisting and phylogenetically related species, the three- and nine-spined stickleback. Populations occur across very similar environmental clines in biotic and abiotic conditions (salinity, oxygen concentration, predation, parasites and prey), and were sampled within exactly the same spatial matrix. In each species we assessed gene flow between populations from contrasting environments and determined divergence in ecologically relevant traits (body shape, armour, spleen size, and trophic morphology). An analyses of genome-wide differentiation was used to identify the genomic basis of adaptation. Based on these data we compared the relative strength of divergent selection and gene flow in both species, as well as the biological functions of the genes under selection. We discuss how these relationships explain how both stickleback species maintain partially overlapping habitats.