The European green crab, Carcinus maenas , has a native distribution that extends from Norway to Mauritania. It has attracted attention because of its recent invasions of Australia, Tasmania, South Africa, Japan and both coasts of North America. To examine the population structure of this global invader in its native range, we analysed a 502‐base‐pair fragment of the mitochondrial cytochrome c oxidase I (COI) gene from 217 cra...