Results

A total of 2,198 samples were collected (2,099 fecal and 99 blood blot). 1,970 were successfully scored (average success rate of 91.4%), and 933 unique individuals were identified (Table 2). Overall, the average dropout rate was 0.0028% and the average false allele rate was 0.011%. Pedigree reconstruction inferred 310 females and 319 males, for a total familial network of 1,562 individuals. 355 inferred and sampled males and 360 inferred and sampled females were identified as parents. 1,487 (95.2%) individuals were linked in one network, with the remaining 75 individuals linked in five smaller clusters (Figure S2.1). We used the 1,487 individuals identified in the primary network for calculating node-based metrics of centrality.

Spatial network analysis

Local area networks

We identified 18 local area networks in order to determine the cohesiveness and centrality of individuals. The local areas with the lowest edge-to-node ratios were all located in the northern Boreal Shield, with the high edge-to-node ratio areas found further south in the western Boreal Plains and southern Boreal Shield (Figure 1). We found significant differences between the distribution of centrality metrics between high and low edge-to-node ratio local areas (Table S2.2, Figure 2). The largest edge-to-node ratio was Canoe Lake in the western Boreal Plains (ratio of 15; Table S2.1, Figure S2.3). We identified three other local areas with similarly high edge-to-node ratios (Figure S2.4, Figure S2.5, Figure S2.6, Table S2.1). The smallest edge-to-node ratio (Central SK Shield) had zero parent-offspring relationships (Table S2.1; Figure S2.7). We identified two other local areas with similarly low edge-to-node ratios, with very few parent-offspring relationships occurring within these local areas (Figure S2.8-Figure S2.9, Table S2.1), indicating that Boreal Shield individuals are not presenting the same proximity to related individuals as observed in the Boreal Plains. Overall, edge-to-node ratios correlated positively to closeness (Figure S2.2A), alpha (Figure S2.2C), betweenness (Figure S2.2D), and degree centrality (Figure S2.2E). However, edge-to-node ratios decreased with eccentricity centrality (Figure S2.2B).
When bringing in the first neighbours of all individuals within a local area, the high edge-to-node ratio areas formed a tighter cluster of individuals than in the low edge-to-node ratio areas. Including first neighbours in the area with the highest edge-to-node ratio (Canoe Lake) increased the ratio to 1.14 and connected 73.6% of individuals into one cluster (Figure S2.3). A large proportion of each high edge-to-node ratio local area became connected into one or two large clusters with the inclusion of first neighbours (Figure S2.4, Figure S2.5, Figure S2.6). In comparison, including first neighbours in the lowest edge-to-node ratio local area (Central SK Shield) increased the ratio to 0.86, but did not connect many individuals into one cluster (only 12.8% of individuals; Figure S2.7). The large variation in local area edge-to-node ratios show that individuals within the high edge-to-node ratio areas in the Boreal Plains and southern Boreal Shield are forming tighter family groups (high number of parent-offspring relationships within each local area).

Full network

Individuals from high edge-to-node ratio local areas were located more centrally within the full family network and clustered with other individuals from the same local area. Individuals from low edge-to-node ratio local areas were dispersed throughout the network and primarily found on the outer edges of the network (Figure 3). Although all local areas were of similar geographic size (Figure 1), individuals from low edge-to-node ratio local areas were not closely connected to each other in the network. Individuals from these local areas were not found within a few edges of other individuals from the same local area, indicating that individuals encountered in each low edge-to-node ratio local area are from different familial lines, or are dispersers that were sampled in that local area (Figure 3); as the edges in the familial network represent parent-offspring relationships, these individuals are likely not highly related to one another, and do not form a cohesive social group. In contrast, individuals from high edge-to-node local areas were highly connected to one another within the full network, indicating they are closely related, with a high density of familial ties (parent-offspring relationships).
Removal of edges with high betweenness did not alter the overall network structure (Figure S2.10). Most edges within the network had low betweenness centrality (score of 1 – 81.5% of edges; Table 3). Only 2.97% of edges were removed after sequentially removing edges with the highest edge betweenness score until only edges with an edge betweenness > 4 remained (Table 3), with no clear delineation of groups within the main network (Figure S2.10), but the removal of these edges led to individuals becoming disconnected from the main network. The high edge-to-node ratio local areas of Canoe Lake, Peter Pond Lake, and SK2West remained central and clustered within the edge removal network (Figure S2.10). Individuals from Trade Lake maintained a high level of clustering, but became separated from the main network, forming a separate subgroup (Figure S2.10). Removal of high betweenness edges did not result on individuals from low edge-to-node ratio areas becoming separate subgroups; individuals remained dispersed throughout the network (Figure S2.10).