Using population and individual derived genetic networks to detect hierarchical genetic population structure and patterns of movement and connectivity of caribou in Western Canada

Background/Question/Methods

: There are many approaches used to investigate genetic variation, distribution, and movement of species across space and time that have significant management and conservation implications. Genetic network methods have been developed to specifically analyse genetic variation across the landscape, and to answer questions of movement and connectivity with great flexibility and relatively few prior assumptions. In this study, multiple genetic network analyses were used to investigate genetic structure and connectivity of caribou across different ecotypes at multiple spatial scales. Population-based genetic networks pruned using a conditional-independence principle method were constructed from a large dataset genotyped at 9 microsatellite loci that included boreal, northern mountain and barren-ground caribou from the Northwest Territories, the east side of the Yukon, northern Alberta, and a small portion of northwestern Saskatchewan. For a subset of samples from the Mackenzie Mountains Region of the Northwest Territories that were genotyped at 15 microsatellite loci, individual-based networks were constructed using a relatedness estimator as well as a reconstructed pedigree in order to supplement the population-based networks, and further investigate fine scale patterns of connectivity and movement in the area of interest.

Results/Conclusions

: A community detection algorithm was used to partition the population-based genetic network at multiple spatial scales which uncovered patterns of hierarchical genetic structure and highlighted patterns of gene flow. The hierarchical population structure results had concordance with the known distribution of different caribou ecotypes and additional structure was found within each ecotype. The betweenness centrality network metric varied amongst migratory and more sedentary ecotypes and increased betweenness centrality was found in areas of importance to gene flow, which connect otherwise disconnected communities. Individual-based networks that were constructed with a subset of samples from the Mackenzie Mountains region of the Northwest Territories revealed patterns of long-distance movement and high connectivity across the region which further supported the results of the population-based networks. Using a combination of population-based and individual-based genetic networks can reveal population structure at multiple scales and allow for better interpretation of the fine scale movements that lead to such structure, including highlighting important areas that facilitate connectivity.