Fig 1.
Caribou sampled in western North America.
Black numbered circles indicate sampled populations (also referred to as “herds”, as they might not be genetically or ecologically distinct). Grey-scale polygons show the distribution of subspecies and ecotypes: diagonal black lines represent the Barren-ground subspecies (R. t. groenlandicus); horizontal lines, light gray, and black represent Northern Mountain, Boreal and Central Mountain, ecotypes, respectively, within the Woodland caribou subspecies (R. t. caribou). Basemap layers available from: https://www12.statcan.gc.ca/census-recensement/2011/geo/bound-limit/bound-limit-eng.cfm and https://international.ipums.org/international/gis.shtml.
Fig 2.
Caribou genetic clusters in western North America.
(A)/(B) and (C)/(D) show the best and second best number of clusters (K = 2 or 3, respectively) describing population structure. Further subdivisions (K>3) were not supported by the program Admixture. Pie charts (A and C) and bar plots (B and D) indicate proportions of ancestry for each individual. Subspecies and ecotype belonging of individuals are indicated to the right of the bar plots: BG refers to the Barren-ground subspecies; NM, CM and Boreal refer to the Northern Mountain, Central Mountain and Boreal ecotypes, respectively, within the Woodland subspecies. For NM individuals we also indicate their location in either Yukon (NM-Y, further North), or British Columbia (NM-B) provinces. Basemap layer available from https://www12.statcan.gc.ca/census-recensement/2011/geo/bound-limit/bound-limit-eng.cfm and https://international.ipums.org/international/gis.shtml.
Fig 3.
Principal component analysis (PCA) plots of caribou individuals in western North America.
Each dot represents a caribou and colors in panels (A) and (B) represent groupings at K = 2 and K = 3, respectively, determined using the program Admixture (see Fig 2). PCA was calculated examining 28K SNP data.
Fig 4.
Occurrence of migratory behavior across caribou ecotypes.
Histograms represent number of individuals in each ecotype with varying degrees of seasonal ranges overlap. In this study, we correlated genetic traits with this information: sedentary behaviour tendency represented by seasonal ranges overlap—a continuous variable.
Fig 5.
Seasonal movement patterns monitored with GPS-collars for a migratory caribou and for a sympatric resident caribou.
(A) and (C) show winter and summer locations. For each caribou (A) shows a complete separation of the seasonal ranges, typical of a migratory animal, while the animal in (C) has ranges overlap and is considered sedentary. (B) and (D) show Net Square Displacement (NSD) plots for the same individuals, between a starting telemetry location and each subsequent location in a year period. (B) The displacement is best represented by a bell curve (marked with continuous line above) when the animal is migratory. (D) An animal is classified as sedentary when the best fitting line quickly reaches an asymptote. Dark grey dots represent actual telemetry locations. Solid lines represent the best fitted models, whereas other lines represent unsupported models of seasonal movement (mixed-migrant, nomad or disperser). In this study, we correlated genetic traits with NSD characterization of individuals as migrants. Basemap layers available from: https://www12.statcan.gc.ca/census-recensement/2011/geo/bound-limit/bound-limit-eng.cfm and https://open.canada.ca/data/en/dataset/957782bf-847c-4644-a757-e383c0057995.
Table 1.
Candidate genes associated with migratory behavior in caribou.
Fig 6.
Regression plots between migratory tendency and proportion of genetic ancestry.
(A) The overlap of seasonal ranges (Index of Overlap, IO, lower in migrants) was negatively dependent upon an individual’s proportion of assignment (Q) to the North cluster, determined using the program Admixture. Individual observations at K2 and K3 (i.e. clusters detected) are marked with circles and crosses, respectively. (B) The probability of being migratory as indicated by Net Square Displacement (NSD) was positively dependent upon an individual’s belonging to the North cluster also obtained at both K = 2 (continuous line) and K = 3 (broken line). Panel B includes results of logistic regression, thus indicating a predicted relationship between a genetic trait and migration that is valid for any caribou.
Table 2.
Dependence of individual caribou migration upon ancestry, while statistically controlling for ecotype.