Ecological adaptation in European eels is based on phenotypic plasticity

Area of Science:

• Evolutionary ecology
• Genetics
• Marine biology

Background:

• European eels exhibit complex life cycles with migrations between the Sargasso Sea and European freshwater/brackish environments.
• Previous studies yielded conflicting evidence on whether European eel populations are genetically distinct or panmictic.

Purpose of the Study:

• To determine if European eel populations are genetically differentiated or panmictic.
• To investigate the roles of genetic adaptation versus phenotypic plasticity in European eel evolution.

Main Methods:

• Whole-genome sequencing of European eel populations.
• Analysis of geographical genetic differentiation.
• Assessment of allele frequency changes between cohorts.

Main Results:

• European eels constitute a single panmictic population with no significant geographical genetic differentiation.
• Spawning and embryonic development in the Sargasso Sea likely create uniform conditions, preventing local adaptation.
• Within-generation selection has a minimal impact on allele frequencies, suggesting it's not a primary driver of adaptation.

Conclusions:

• Phenotypic plasticity is the predominant mechanism enabling European eels to cope with diverse environmental conditions during postlarval stages.
• This study resolves a long-standing question about the evolutionary ecology of the European eel.