Range-wide parallel climate-associated genomic clines in Atlantic salmon

Area of Science:

• Evolutionary Biology
• Population Genetics
• Genomics

Background:

• Intraspecific diversity is shaped by local adaptation across environmental gradients.
• Atlantic salmon (Salmo salar) populations exhibit variation that can provide insights into evolutionary processes.

Purpose of the Study:

• To evaluate latitudinal variation in allele frequency in North American and European Atlantic salmon populations.
• To identify genomic regions associated with climate adaptation in Atlantic salmon.
• To investigate patterns of parallel evolution and genetic architecture between continents.

Main Methods:

• Utilized 1773 genome-wide single nucleotide polymorphisms (SNPs).
• Analyzed allele frequency variation across 134 populations.
• Employed logistic regression to associate genetic clines with environmental factors like latitude and temperature.

Main Results:

• Detected significant clinal variation in allele frequencies at 84 loci in North America and 195 loci in Europe.
• Identified 12 common clinal loci between continents, distributed evenly across the genome.
• Found significant associations between clinal SNPs and latitude, particularly average spring temperature.
• Parallel clines were linked to metabolic and immune functions, suggesting climate-driven adaptive differentiation.

Conclusions:

• Evidence of large-scale, climate-associated environmental differences across the North Atlantic.
• Supports patterns of parallel evolution in Atlantic salmon on both sides of the Atlantic, with shared and divergent genetic underpinnings.
• Genomic clines highlight the roles of selection and demographic processes in shaping intraspecific diversity and provide a framework for assessing climate change impacts.