Genomic insights into the origin of ecotypes

A century after Turesson introduced ecotypes as locally adapted subunits of species, their origins and nature remain debated. Recent advances in molecular ecology have breathed new life into the ecotype concept and significantly expanded our understanding of how ecotypes form. Here, we clarify how ecotypes can be distinguished from other forms of local adaptation, outline criteria for their recognition, and synthesise evidence on the ecological and evolutionary processes that give rise to them. We then evaluate what genomics has uncovered about the origin of ecotypes, revealing pronounced roles of pre-existing variation, large-effect loci, structural variants, gene regulation, and complex demographic histories. Our framework refines Turesson's concept and highlights outstanding questions about the predictability, persistence, and evolutionary significance of ecotypes.