Population genomics of the introduced and cultivated Pacific kelp Undaria pinnatifida: marinas — not farms — drive regional connectivity and establishment in natural rocky reefs

Ports and farms are well-known primary introduction hotspots for marine non-indigenous species (NIS). The extent to which these anthropogenic habitats are sustainable sources of propagules and influence the evolution of NIS in natural habitats was examined in the edible seaweed Undaria pinnatifida, native to Asia and introduced to Europe in the 1970s. Following its deliberate introduction 40 years ago along the French coast of the English Channel, this kelp is found in three contrasting habitat types: farms, marinas, and natural rocky reefs. In light of the continuous spread of this NIS, it is imperative to better understand the processes behind its sustainable establishment in the wild. In addition, developing effective management plans to curtail the spread of U. pinnatifida requires determining how the three types of populations interact with one another. In addition to an analysis using microsatellites, we developed, for the first time in a kelp, a ddRAD-sequencing technique to geno...