Gene Flow and Local Adaptation in Species Ranges

Species occupy geographic ranges that often span heterogeneous environments, creating a balance between dispersal of genetic material and the fine-tuning of local genotypes to distinct conditions. Gene flow—the movement of alleles among populations—can introduce variation that fuels adaptive responses to shifting climates or novel habitats, yet excessive influx of maladapted alleles may swamp locally beneficial gene combinations. Meanwhile, local adaptation arises when natural selection favours traits optimised to particular thermal, moisture or biotic regimes at range margins, enhancing population persistence despite isolation or small size. The interplay of these processes shapes range limits: at core regions, abundant gene flow sustains high diversity and potential for adaptation, whereas at edges, genetic drift and founder effects can erode variation, slowing or halting adaptation. Environmental gradients in elevation, latitude or habitat structure further modulate the relative strength of selection and dispersal, yielding steep margins where adaptation fails or gradual clines of phenotype matching. Understanding the genomic architecture underlying adaptation, the demographic context of dispersal, and the ecological drivers of selection is crucial for predicting species’ responses to ongoing global change, informing conservation strategies such as assisted gene flow to bolster marginal populations.

Research from Nature Portfolio

Recent studies have revealed the multidimensional nature of selection landscapes within and between species. In closely related wildflowers, reciprocal transplant experiments across multiple sites demonstrated that one suite of traits governs divergence between species, while an independent suite underlies adaptation within species. This work highlights how selection can simultaneously drive speciation and maintain extensive within-species diversity, underscoring the complexity of adaptive landscapes across spatial scales.

Gene Flow and Local Adaptation in Species Ranges publication trend

The graph below shows the total number of articles in gene flow and local adaptation in species ranges across all publications each year (not limited to Nature Index journals).

Technical terms

Gene flow: Movement of alleles among populations through dispersal or migration, influencing genetic diversity and adaptation.

Local adaptation: Evolutionary process by which populations evolve traits that maximise fitness in their specific environmental context.

Environmental gradient: Continuous change in abiotic or biotic factors (e.g. temperature, elevation) across a landscape.

Genetic drift: Random fluctuations in allele frequencies, particularly impactful in small or isolated populations.

Effective population size: Number of individuals in a population contributing genetically to subsequent generations, affecting drift and inbreeding.

Reciprocal transplant experiment: Field study design in which organisms from different populations are swapped among sites to test for local adaptation.

References

1. A multidimensional selective landscape drives adaptive divergence between and within closely related Phlox species. Nature Communications (2024).
2. Unravelling drivers of local adaptation through evolutionary functional–structural plant modelling. New Phytologist (2024).
3. Drivers of strong isolation and small effective population size at a leading range edge of a widespread plant. Heredity (2023).
4. Rapid evolution of novel biotic interactions in the UK Brown Argus butterfly uses genomic variation from across its geographical range. Molecular Ecology (2023).