Figure 1.

(a) Population distribution, potential trade routes, and sample locations of Atlantic walrus in the northern Atlantic region. The range of modern Atlantic walrus (dark grey) and dispersal routes (black arrows) follow [47] and [31]. Eight breeding populations are recognized [47]; (1) Foxe Basin, (2) Hudson Bay, (3) Hudson Strait, (4) West Greenland, (5) North Water, (6) East Greenland, (7) Svalbard/Franz Josef Land, (8) Novaya Zemlya. Trade routes from Greenland—including the location of Norse settlements—and northern Fennoscandia/Russia (brown) indicate possible sources from which walrus ivory was exported during the Middle Ages. The Svalbard specimens (orange) were originally from hunting stations of the 1700s and 1800s. The other Atlantic walrus specimens (red, grey) were obtained from museum collections. (b) Bayesian phylogenetic tree obtained using BEAST [48] based on 346 mitochondrial single nucleotide polymorphisms (SNPs) using Pacific walrus (PAC) as an outgroup. Numbers represent the different specimens listed in electronic supplementary material, table S1. The colour of the numbers (grey, red, orange) match the sampling locations as in (a). Branches with a posterior probability of one (grey circles) are indicated. (c) Distribution of RFLP and control region (CR) haplotypes of modern Atlantic walrus. The RFLP clade classification follows [30]. The distribution of a distinct ACC CR haplotype is from 306 specimens (see Methods).