Genetic rescue is the intentional increase of gene flow into a small, isolated population to raise heterozygosity and reduce inbreeding depression, with the aim of improving population fitness and persistence. This approach addresses genetic problems caused by low population size and prolonged isolation, where genetic drift and mating among relatives can fix deleterious alleles and lower survival or reproductive success.
Mechanisms and evidence
The primary mechanisms are increased genetic variation, masking of recessive deleterious alleles, and restored adaptive potential. Empirical synthesis by Richard Frankham Australian National University documents consistent, positive responses in many taxa following gene flow, providing broad evidence that genetic rescue often yields measurable gains in survival, reproduction, or growth. Reviews by Anna R. Whiteley University of Montana and colleagues further explain how even limited immigration can produce rapid fitness benefits, while emphasizing that outcomes are shaped by the genetic and ecological context.
Risks, long-term dynamics, and contextual factors
Genetic rescue is not a universal cure. Risks include outbreeding depression when genetically divergent sources disrupt local adaptations, and demographic swamping if immigrant numbers overwhelm small native groups. The long-term benefit depends on maintaining connectivity or repeated introductions where natural corridors are absent. Habitat quality, disease exposure, and human land use determine whether increased genetic variation translates into enduring population recovery. Cultural and territorial considerations are critical: translocations require consent from local communities, coordination across jurisdictions, and careful planning to respect Indigenous rights and local livelihoods.
Monitoring and adaptive management are essential because initial fitness gains do not guarantee persistence. Genetic metrics should be paired with demographic and ecological monitoring to detect evolving trade-offs between introduced variation and local adaptation. In many systems, genetic rescue has been a pragmatic conservation tool when combined with habitat protection and landscape-scale planning. When applied with transparent stakeholder engagement and long-term stewardship, it can shift the trajectory of declining, isolated populations toward recovery.