Detecting Local Adaptation between North and South European Atlantic Salmon Populations.

Area of Science:

• Genomics
• Evolutionary Biology
• Conservation Genetics

Background:

• Atlantic salmon (Salmo salar) populations in the Iberian Peninsula have declined due to anthropogenic factors.
• Previous restocking efforts using salmon from northern latitudes failed, likely due to poor adaptation to warmer Iberian waters.

Purpose of the Study:

• To investigate local adaptation in Iberian Atlantic salmon populations by comparing their genomes with Scottish populations.
• To identify candidate single nucleotide polymorphisms (SNPs) responsible for adaptive differences and explain restocking failures.

Main Methods:

• Genotyping of Iberian (Atlantic and Cantabric) and Scottish Atlantic salmon populations using a high-density SNP array (220,000 SNPs).
• Analysis of genomic data to detect patterns of divergent selection between populations.

Main Results:

• Evidence of local adaptation was found in North Spanish and Scottish populations.
• Significant genomic differences were observed between Iberian and Scottish populations, and also between Atlantic and Cantabric Iberian populations.
• Identified genes are associated with development, cellular metabolism, DNA transcription, and anatomical structure.
• A specific SNP within the NADP-dependent malic enzyme-2 (mMEP-2*) gene was identified as a candidate for local adaptation.

Conclusions:

• Iberian Atlantic salmon populations exhibit local adaptation, a key factor in their evolutionary history.
• Genomic divergence supports the failure of past restocking efforts and underscores the importance of considering local adaptation in conservation.
• The identified candidate SNPs, particularly within mMEP-2*, provide insights into the genetic basis of adaptation in Atlantic salmon.