Abstract
Understanding how populations adapt to local environments is increasingly important to prevent biodiversity loss due to climate change. Here we examined whole-genome variation of 12 Atlantic horse mackerel pool samples from the North Sea to north Africa, and the western Mediterranean Sea. This marine migratory benthopelagic fish is one of the most widely distributed and commercially important species in the eastern Atlantic. We found low population structure at neutral loci, but high differentiation at adaptive loci distinguishing the western Mediterranean and the North Seas from other Atlantic locations. Candidate genes distinctive of the Mediterranean include a green-sensitive-opsin harbouring two missense mutations that might fine-tune the spectral sensitivity to blue-green light conditions. Candidate genes characteristic of the North Sea could play a critical role in cold tolerance (energy metabolism and cell membrane structure) and increased sensitivity to odours, presumably to compensate reduced visibility in turbid waters. We also discovered a massive chromosomal inversion (9.9 Mb) that underlies a climate-related latitudinal cline with a break near mid Portugal. Genome-environment association analysis indicated that sea water dissolved oxygen concentration and temperature are likely the main environmental drivers of local adaptation. Our genomic data broadly supports the current ICES stock divisions, but recommends revision of the western and southern stock boundaries. We developed a reduced SNP panel that genetically discriminate the North Sea from neighbouring populations. Our study highlights the importance of life history and chromosomal inversions in adaptation with gene flow, and the complexity of evolutionary and ecological processes involved in local adaptation.
Competing Interest Statement
The authors have declared no competing interest.
