Data from: Genetic connectivity for two bear species at wildlife crossing structures in Banff National Park

Roads can fragment and isolate wildlife populations, which will eventually
decrease genetic diversity within populations. Wildlife crossing
structures may counteract these impacts, but most crossings are relatively
new, and there is little evidence that they facilitate gene flow. We
conducted a three-year research project in Banff National Park, Alberta,
to evaluate the effectiveness of wildlife crossings to provide genetic
connectivity. Our main objective was to determine how the Trans-Canada
Highway and crossing structures along it affect gene flow in grizzly
(Ursus arctos) and black bears (Ursus americanus). We compared genetic
data generated from wildlife crossings with data collected from greater
bear populations. We detected a genetic discontinuity at the highway in
grizzly bears but not in black bears. We assigned grizzly bears that used
crossings to populations north and south of the highway, providing
evidence of bidirectional gene flow and genetic admixture. Parentage tests
showed that 47% of black bears and 27% of grizzly bears that used
crossings successfully bred, including multiple males and females of both
species. Differentiating between dispersal and gene flow is difficult, but
we documented gene flow by showing migration, reproduction and genetic
admixture. We conclude that wildlife crossings allow sufficient gene flow
to prevent genetic isolation.