Genetic Structure and Invasion Ecology of Salmonids in South America

Salmonid species introduced to South America over the past century have established widespread populations with complex genetic backgrounds. Multiple introduction events—from both deliberate stocking and unintentional aquaculture escapes—have delivered distinct North American lineages of Chinook salmon, rainbow trout and Atlantic salmon into Chilean and Argentinean river basins. High propagule pressure associated with fish farming has maintained or even elevated genetic diversity in founder populations, counteracting the loss of variation through genetic drift. Admixture among donor stocks has generated polyphyletic assemblages that may confer broad adaptive potential. Life-history variation, including anadromous migrations versus resident forms, interacts with river geomorphology, water chemistry and native fish assemblages to shape patterns of gene flow, local adaptation and ecosystem impact. Emerging genomic tools, such as high-density SNP panels, are refining our understanding of demographic history, population connectivity and the genomic basis of invasion success, informing strategies to mitigate ecological risks and preserve native biodiversity.

Research from Nature Portfolio

Analyses of microsatellite markers in expanding Patagonian Chinook salmon populations have revealed a polyphyletic ancestry derived from multiple North American donor regions. Latitudinal clines in lineage composition correspond to different introduction pathways—early net-pen aquaculture versus open-ocean ranching—and demonstrate that admixture among distinct stocks complicates assignments of origin but may enhance adaptive breadth. Although these populations display high genetic diversity, the contribution of this variation to local adaptation and fitness in novel environments remains an open question, guiding future investigations into genotype–environment interactions and evolutionary trajectories in invasive salmonids.

Genetic Structure and Invasion Ecology of Salmonids in South America publication trend

The graph below shows the total number of articles in genetic structure and invasion ecology of salmonids in south america across all publications each year (not limited to Nature Index journals).

Technical terms

Microsatellite locus: A DNA marker consisting of short, tandemly repeated sequence motifs, highly polymorphic and used to assess genetic diversity and population structure.

Single nucleotide polymorphism (SNP): A single base-pair change in the genome that serves as a precise marker for genetic variation and demographic inference.

Propagule pressure: The combined number and frequency of individuals introduced to a new region, which influences the likelihood of establishment.

Admixture: The process by which individuals from genetically distinct populations interbreed, producing mixed-ancestry offspring.

Effective population size (Ne): The size of an idealised population that would lose genetic variation at the same rate as the observed population, reflecting the number of individuals contributing genes to subsequent generations.

References

1. Polyphyletic ancestry of expanding Patagonian Chinook salmon populations. Scientific Reports (2017).
2. Population structure and genetic diversity of rainbow trout (Oncorhynchus mykiss) broodstocks from Brazil using SNP markers. Aquaculture Reports (2023).
3. Genetic signals of artificial and natural dispersal linked to colonization of South America by non‐native Chinook salmon (Oncorhynchus tshawytscha). Ecology and Evolution (2018).
4. Genetic structure and origin of non-native, free-living Atlantic salmon Salmo salar along a latitudinal gradient in Chile, South America. Aquaculture Environment Interactions (2022).