Contrasting genetic trajectories of endangered and expanding red fox populations in the western U.S.

As anthropogenic disturbances continue to drive habitat loss and range
contractions, the maintenance of evolutionary processes will increasingly
require targeting measures to the population level, even for common and
widespread species. Doing so requires detailed knowledge of population
genetic structure, both to identify populations of conservation need and
value, as well as to evaluate suitability of potential donor populations.
We conducted a range-wide analysis of the genetic structure of red foxes
in the contiguous western U.S. with the objectives of contextualizing
field observations of relative scarcity in the Pacific mountains and
increasing abundance in the cold desert basins of the Intermountain West.
Using 31 autosomal microsatellites, along with mitochondrial and
Y-chromosome markers, we found that populations of the Pacific mountains
were isolated from one another and genetically depauperate (e.g.,
estimated Ne range = 3–9). In contrast, red foxe s in the Intermountain
regions showed relatively high connectivity and genetic diversity.
Although most Intermountain red foxes carried indigenous western
matrilines (78%) and patrilines (85%), the presence of nonindigenous
haplotypes at lower elevations indicated admixture with fur-farm foxes and
possibly expanding midcontinent populations as well. Our findings suggest
that some Pacific mountain populations could likely benefit from increased
connectivity (i.e., genetic rescue) but that nonnative admixture makes
expanding populations in the Intermountain basins a non-ideal source.
However, our results also suggest contact between Pacific mountain and
Intermountain basin populations is likely to increase regardless,
warranting consideration of risks and benefits of proactive measures to
mitigate against unwanted effects of Intermountain gene flow.