Back to the future: What population genomics and paleogenomics reveal on spatio- temporal stock structure, connectivity and adaptation in the Atlantic bluefin tuna

A genotyping-by-sequencing approach was used to discover SNPs throughout the Atlantic Bluefin tuna genome while simultaneously analyzing population structure in the Gulf of Mexico, Atlantic and Mediterranean, including several previously uncharacterized sites. Genotyping revealed temporally persistent differentiation among baseline, early life stage samples from the western Atlantic and Mediterranean using panels of 80 and 25 SNPs (FST = 0.0091, p<0.001 and FST = 0.028, p<0.001, respectively) and an average self-assignment success rate of 83.8%. No clear pattern of structuring was detected among Mediterranean samples. The assignment (overall probability 82.2%) and mixture analyses of mixed feeding aggregations in the Atlantic Ocean and Mediterranean revealed an extensive mixing in the Atlantic Ocean, particularly in the Gulf of St. Lawrence, as well as a poleward shift in the distribution of eastern migrants in the Western Atlantic and ontogeny-dependent migratory behavior. Parallel ongoing researches are also exploiting Bluefin paleogenomic resources retrieved from Atlantic, Mediterranean and Marmara-Black Sea historical remains from late Iron Age, Ancient Roman, Byzantine and modern eras. Significant differences in geographic and temporal SNP allele frequencies are revealed at several functional genes. By comparing the contemporary and historical genetic codes we are making efforts to shed light on the evolution of the species genome in response to nearly two millennia of fisheries pressure, a changing climate and pollution of the sea.