Genetic rescue in an inbred Arctic fox (Vulpes lagopus) population

Abstract

Isolation of small populations can reduce fitness through inbreeding depression and impede population growth. Outcrossing with only a few unrelated individuals can increase demographic and genetic viability substantially, but few studies have documented such genetic rescue in natural mammal populations. We investigate the effects of immigration in a subpopulation of the endangered Scandinavian arctic fox (), founded by six individuals and isolated for 9 years at an extremely small population size. Based on a long-term pedigree (105 litters, 543 individuals) combined with individual fitness traits, we found evidence for genetic rescue. Natural immigration and gene flow of three outbred males in 2010 resulted in a reduction in population average inbreeding coefficient (), from 0.14 to 0.08 within 5 years. Genetic rescue was further supported by 1.9 times higher juvenile survival and 1.3 times higher breeding success in immigrant first-generation offspring compared with inbred offspring. Five years after immigration, the population had more than doubled in size and allelic richness increased by 41%. This is one of few studies that has documented genetic rescue in a natural mammal population suffering from inbreeding depression and contributes to a growing body of data demonstrating the vital connection between genetics and individual fitness.

Genomic and Fitness Consequences of Genetic Rescue in Wild Populations

“…To what extent this scenario translates to other organisms, including species of conservation concern, is unknown. However, our results agree with a growing body of literature supporting the idea that gene flow from a closely related source into small, genetically depauperate populations can produce substantial demographic benefits [17][18][19][20]. These studies support a proposed paradigm shift in the genetic management of small populations from the current default of inaction to a new policy that considers restoring gene flow to recently fragmented populations [21].…”

Genetic rescue without genomic swamping in wild populations

“…To what extent this scenario translates to other organisms, including species of conservation concern, is unknown. However, our results agree with a growing body of literature supporting the idea that gene flow from a closely related source into small, genetically depauperate populations can produce substantial demographic benefits ( 12, 13, 28, 29 ). These studies support a proposed paradigm shift in the genetic management of small populations from the current default of inaction to a new policy that considers restoring gene flow to recently fragmented populations ( 30 ).…”

Does gene flow aggravate or alleviate maladaptation to environmental stress in small populations?

“…We would emphasize that the ability of individuals to endure chronic or novel stress is a component of fitness, but that the relationship between stress responses and overall fitness likely depends on a number of other factors, including the realized reproductive success of individuals exposed to stress, potential trade‐offs between the ability to respond to stress and other fitness components, and the frequency of exposure to stress. As demonstration of positive fitness outcomes of restored gene flow accumulates (Hasselgren et al, ; Hogg, Forbes, Steele, & Luikart, ; Hufbauer et al, ; Johnson et al, ; Kronenberger et al, ; Madsen, Shine, Olsson, & Wittzell, ; Robinson et al, ) and calls for gene flow manipulation grow louder (Ralls et al, ; Whiteley et al, ), it will also be critical to understand the extent and mechanisms by which new gene flow affects immediate and long‐term response to environmental stress. In some cases of abrupt stress, such as high‐temperature exposure in our study, gene flow may increase initial tolerance and reduce extinction probability.…”