Low-coverage re-sequencing of European eel and American eel individuals

The relative role of genetic adaptation and phenotypic plasticity is of fundamental importance in evolutionary ecology. European eels have a complex lifecycle including transitions between life stages across ecological conditions in the Sargasso Sea, where spawning occurs, to those in brackish and freshwater bodies from Northern Europe to Northern Africa. Here we use whole-genome analysis and show that European eels belong to one panmictic population. We demonstrate a complete lack of geographical genetic differentiation, which is possible because the most critical life stages - spawning and embryonic development - take place under near identical conditions. Our results strongly indicate plasticity as the predominant mechanism for eel adaptation to diverse environmental conditions during post larval stages, ultimately solving a longstanding question for a classically enigmatic species.