Using whole genomes to understand the value of genetic rescue for montane red foxes
In small wildlife populations, breeding among related individuals – or “inbreeding” – can negatively affect population growth and lead to decline. This can be mitigated by bringing in breeding adults from another population to implement “genetic rescue” by adding new genetic material, but the action comes with additional uncertainty and risk. In the past, addressing this uncertainty was often so expensive and challenging that genetic rescue was rarely implemented, but a newer method called “genomic sequencing” can clarify this uncertainty to make genetic rescue more feasible. In this study, scientists used genomic sequencing to assess the risks and benefits of translocating endangered montane red foxes to help their populations recover and found that genetic rescue may be viable in some cases.
Cate Quinn, research biological scientist with the USDA Forest Service Rocky Mountain Research station, and collaborators first sequenced whole genomes (or complete sets of genetic material) from 28 individual foxes across the four subspecies of montane red foxes. They then used genomic technology to look backwards through time to understand how current patterns of population isolation and inbreeding are different from historical patterns. They found high levels of recent inbreeding in Sierra Nevada and Lassen red fox populations; in fact, only one new fox entered the Lassen population over the last 20 years. But 10-12,000 years ago, the story was very different: montane red foxes were abundant and well-connected across the western United States. Ultimately, this history of genetic connection across montane red fox populations sets up the more isolated populations as good candidates for genetic rescue.
In particular, the Lassen population is a candidate for genetic rescue due to its isolation and the strong evidence of inbreeding. However, the success of any effort is uncertain because there are likely less than 30 individuals remaining, meaning that increased variation in the population’s response around the time of the genetic rescue could temporarily increase extinction risk. To address these concerns, managers are carefully considering ideal source populations of translocated individuals that would strike a balance between risks and a successful genetic rescue.