Figure 3.

Geographic distribution, mtDNA haplotype distribution, and autosomal AFLP based admixture proportions of European herring gull (L. argentatus) populations. The geographical distribution of the two European herring gull subspecies are indicated in solid dark blue (western subspecies argenteus), and light blue (north-eastern subspecies argentatus). Their geographical overlap (striated area) is also shown. Two mtDNA HVR1 sequence haplotype groups were identified (Additional file 1, Figure 2, Additional file 2, and reference [8]): clade 1 and clade 2. For each of the 16 herring gull colonies the black pie chart area reflects the relative frequency of individuals with clade 1 mtDNA haplotypes. Similarly, the white area corresponds to clade 2. Also, the exact number of individuals with clade 1 (left) and clade 2 (right) haplotypes and abbreviated colony names (Table 1) are indicated. Two cachinnans haplotypes, shown in grey, are indicated in the Estonian (EST) colony. Clade 1 mtDNA haplotypes are more frequent among northern colonies, whereas clade 2 mtDNA haplotypes are more frequent among southern colonies. There is less congruence between mtDNA haplotype distribution and sub-species: northern Icelandic argenteus displays predominantly clade 1 haplotypes. Eastern Finnish argentatus displays predominantly clade 2 mtDNA haplotypes. The boxed areas define, for each colony, those individuals that we used for the analyses of 230 AFLP loci and cytB sequencing. AFLP genotypes were analysed by STRUCTURE and revealed the presence of four distinct ancestral populations among present day argentatus, here shown with yellow, green, blue, and red. Each individual is represented by a (multi) coloured bar, on top of which there is a black-filled square (clade 1 membership), or a white square (clade 2 membership). The proportion of each colour within a single bar indicates the relative contribution of one of these four ancestral populations to the genome of that individual gull.