Landscape connectivity among island-dwelling caribou – where ice and human activity amplify habitat discontinuity

Background/Question/Methods

Functional connectivity is important to the persistence of wildlife. It facilitates movement and gene flow, and is vital to genetic diversity, metapopulation dynamics, and range shifts in a changing world. Connectivity may be particularly important for large mobile animals. For endangered island-dwelling caribou, known to disperse over large areas including across the Arctic sea ice, the threat of future environmental change is real. Protecting caribou habitat and its linkages depends on identifying such areas at commensurate, broad scales. Using simultaneous multi-surface optimization, we modeled and mapped the drivers of caribou connectivity across ca. 2 million km2 of the Canadian Arctic Archipelago. We assessed hierarchical genetic structure, identified genetically discrete groups and evaluated individual-based landscape genetics within these groups. We tested whether land- and sea-scape heterogeneity (isolation-by-resistance) or geographic distance (isolation-by-distance) influenced gene flow and genetic variation.

Results/Conclusions

We found evidence of both isolation-by-resistance and panmixia with absence of isolation-by-distance, depending on the genetic group considered. For High Arctic caribou, we found that glaciers [elevation], low sea ice concentrations and human trails impeded functional connectivity, while intact sea ice was an important platform for inter-island movements. For Baffin Island caribou, our models suggested that gene flow has been unrestricted, emphasizing that organism-landscape relationships can vary across space. Our study identifies critical movement pathways for an iconic Arctic species and supports broad scale conservation and planning efforts across a vast environment of islands and ice.