Climate-induced range expansions of marine fauna into the Arctic – what is the most likely colonisation route?

As a result of climate change, the Arctic faunas of the Northeast Atlantic have begun to shift in an Atlantic direction. One system exposed to such a change is the Northeast Greenland (NEG) Shelf. However, the colonisation route taken by boreal fauna to the NEG shelf is unknown. This knowledge is essential to predict to what extent boreal fauna will dominate Arctic habitats, and alter ecosystems in the future. For the species under study here, colonisation is possible from either the Barents Sea via a northern route, or via southern expansion from Iceland and Jan Mayen Island. Here, we used microsatellite markers and established reference population genetic data from Atlantic cod (Gadus morhua), beaked redfish (Sebastes mentella) and deep-sea shrimp (Pandalus borealis) to determine the most likely origin of specimens of these species recently collected at the NEG shelf. We demonstrate that all three species originate from the Barents Sea, and suggest that a likely colonisation route is via advection across the Fram Strait. Our results show that the species composition of Arctic habitats can be shaped by the dispersal of pelagic larvae, and that the fauna of the Barents Sea can project on to adjacent Arctic habitats with unknown consequences to the structure and function of putatively isolated Arctic communities.