Figure 3 : Historical relationships and demographic history of North Atlantic Harbour porpoises. (a) Maximum likelihood bifurcating tree inferred by Treemix indicating a post-glacial colonization of harbour porpoises from a southern refugium. The horizontal branch lengths are proportional to the amount of genetic drift. (b) Inferred changes on effective population size (Ne) through time with a mutation rate of 2.56 x 10-8 and a generation time of 11.9 years. The start of the last glacial period (110,000 yBP) and the Last Glacial Maximum (26,500 to 19,000 yBP) are indicated in gray.