Northern areas as refugia for temperate species under current climate warming: Atlantic salmon (Salmo salar L.) as a model in Northern Europe

Abstract

In this work, patterns of geographical genetic diversity in Atlantic salmon Salmo salar were studied across the whole Atlantic arc, as well as whether patterns (and thus genetic population structure) were affected by water temperatures. Salmo salar populations were here characterized using microsatellite loci and then analysed in the light of ocean surface temperature data from across the region. Analysis showed the presence of a latitudinal cline of genetic variability (higher in northern areas) and water temperatures (sea surface temperatures) determining genetic population structure (the latter in combination with genetic drift in southern populations). Under the current global change scenario, northern areas of Europe would constitute refuges for diversity in the future. This is effectively the inverse of what appears to have happened in glacial refugia during the last glacial maximum. From this perspective, the still abundant and large northern populations should be considered as precious as the small almost relict southern ones and perhaps protected. Careful management of the species, coordinated across countries and latitudes, is needed in order to avoid its extinction in Europe.