selection in response to anthropogenic organic and metal contamination in North Atlantic Eels

Measuring the effects of selection on the genome imposed by human-altered environ-ment is currently a major goal in ecological genomics. Given the polygenic basis of most phenotypic traits, quantitative genetic theory predicts that selection is expected to cause subtle allelic changes among covarying loci rather than pronounced changes at few loci of large effects. The goal of this study was to test for the occurrence of poly-genic selection in both North Atlantic eels (European Eel, Anguilla anguilla and Ameri-can Eel, A. rostrata), using a method that searches for covariation among loci that would discriminate eels from ‘control ’ vs. ‘polluted ’ environments and be associated with specific contaminants acting as putative selective agents. RAD-seq libraries resulted in 23 659 and 14 755 filtered loci for the European and American Eels, respec-tively. A total of 142 and 141 covarying markers discriminating European and Ameri-can Eels from ‘control ’ vs. ‘polluted ’ sampling localities were obtained using the Random Forest algorithm. Distance-based redundancy analyses (db-RDAs) were used to assess the relationships between these covarying markers and concentration of 3