Figure 1.
PAC, ATL, and LAP groups are indicated in light gray, dark grey and mottled gray, respectively. Area of MAR historical specimen sampling for this study is shown in black. Atlantic subpopulations are: (1) Foxe Basin, (2) southern and eastern Hudson Bay, (3) northern Hudson Bay/Hudson Strait/northern Labrador, (4) western Greenland, (5) in the ‘North Water’ (Baffin Bay/northeastern Canadian Arctic, (6) eastern Greenland, (7) Franz Josef Land/Svalbard, and (8) Kara Sea/Barents Sea.
Figure 2.
Collection sites for walrus specimens providing morphological data.
Black, gray, and white centered circles denote sites of MAR, PAC, and ATL samples respectively. Table S1 gives specific sample origins.
Table 1.
Number of cranial and mandibular samples for which morphological data were collected from public and private institutions/collections.
Figure 3.
Cranial, tusk and mandibular measurements collected from walrus crania where possible.
Numbers indicate measures taken as described in Table 2. Dashed lines indicate measures taken with a measuring tape. Measure 13 is not shown but is a mediolateral equivalent of measure 12. Images modified from Allen [7].
Table 2.
Morphological measurements taken and corresponding definitions.
Figure 4.
Mastoid width (a) and mandible width (b) versus age in known age males (black) and females (gray) from ATL.
Figure 5.
Collection sites for walrus specimens providing DNA data.
Black, gray, and white centered shapes denote MAR, PAC, and ATL regions respectively. Circles indicate new data collected in this study, stars indicate data presented previously [2]. Not shown on the map are samples from Laptev Sea, Svalbard and Franz Josef Land of Lindqvist et al. [2].
Figure 6.
Boxplots of (a) %DA and (b) %AA.
Whiskers denote minimum and maximum of the data. Boxes denote the 2nd and 3rd quartiles of the data and the squares denote the data mean. For %DA, negative values indicate a left-side asymmetry while positive values indicate a right-side asymmetry.
Table 3.
Regional average percent individual directional asymmetry (%DA) and percent individual absolute asymmetry (%AA) in the MAR and ATL specimens.
Figure 7.
Boxplots for standardized measures of (a) skull, (b) tusk, and (c) mandible data with corresponding t or W values for the comparison of ATL and MAR regions.
Measurement abbreviations correspond to those described in Table 2.
Figure 8.
Discriminant function analysis scatterplots for skull (a), tusk (b), and mandible (c) data.
Embedded is also a plot of the first two eigenvalues of the discriminant analysis. Circles encompass the range of 2/3 of the data points.
Table 4.
Haplotype (h) and nucleotide diversity (π) and corresponding standard error (in parentheses) for PAC, LAP, ATL and MAR regions.
Figure 9.
Median joining network of walrus haplotypes from PAC (dark gray), LAP (light gray), ATL (white) and MAR (black) regions as found in Lindqvist et al. [2] and this study.
In addition, ATL samples from east of Greenland are indicated in blue. Each line segment denotes one sequence difference, except where numbers indicate differences between more divergent sequences. The circle sizes are indicative of haplotype frequencies across the two studies. Small red circles indicate inferred median vectors.
Figure 10.
Phylogenetic tree of mtDNA control region haplotypes identified in this study and by Lindqvist et al. [2].
Samples from LAP, PAC, ATL and MAR are shown highlighted by light gray, dark gray, white, and black, respectively. The Stellar sea lion (Eumetopias jubatus) is used as an outgroup.