Figure 2 : Population structure of North Atlantic Harbour porpoises indicating the existence of five major genetic clusters: Black Sea subspecies, Iberian subspecies, Atlantic, Belt Sea and Proper Baltic Sea populations. (a) Principal Component Analysis (PCA) of harbour porpoises (N = 72) showing the first and second PCs. (b) Admixture analysis of harbour porpoises (N = 72), only K ranging from 2 to 4 is shown. (c) PCA of the dataset without the Black Sea subspecies (N = 67) showing the first and second PCs. (d) Admixture analysis of the dataset without the Black Sea subspecies (N = 67), only K ranging from 2 to 3 is shown. Each small vertical bar in the admixture analyses represent a Harbour porpoise specimen and the colouring corresponds to its genetic ancestry, Black Sea subspecies in black, Atlantic population in red, Belt Sea population in dark blue and Proper Baltic Sea population in light blue.