Sampling localities and genetic differentiation of Fucus species. A. Map of Scandinavia showing the main sampling localities and the sampling sites in Öregrund (SW Gulf of Bothnia), where both species occur in sympatry. B. Two-dimensional representation of a factorial correspondence analysis based on microsatellite genotype data. Genotypes are coloured according to species: F. radicans (red squares) and F. vesiculosus (yellow circles). C. Neighbour-joining microsatellite-based population tree calculated with Cavalli-Sforza genetic distances. Fv denotes F. vesiculosus.