Widespread physical mixing of starry ray from differentiated populations and life histories in the North Atlantic

The starry ray Amblyraja radiata (Donovan, 1808) is widely distributed in the North Atlantic Ocean. Although considered a single species, there is large variation in size-at-maturity in the NW Atlantic, and Red List status ranges from 'Least Concern' in the NE Atlantic via 'Vulner able' in Canadian waters to 'Critically Endangered' in US waters. Previous studies have documented regional morphological, morphometric, and ecological differences, without giving any conclusive evidence on reproductive isolation. Here, we use 10 microsatellite loci and 656 specimens originating from waters off northern Canada, eastern and western Greenland, Svalbard, the Barents Sea, the Norwegian Sea, and the North Sea, to (1) elucidate the population genetic structure of A. radiata, and (2) clarify whether differences in life history within the NW Atlantic is correlated to genetic structuring. The results suggested that A. radiata within the North Atlantic may be divided into 3 major clusters that coincide with the geographical regions NW Atlantic, Greenland and NE Atlantic. However, large physical mixing of individuals from different populations and with differentiated life histories throughout the North Atlantic suggested that glacial periods and biological features have shaped the contemporary distribution and genetic signatures of A. radiata. The differentiated life histories within the NW Atlantic specimens cannot be attributed to a genetic component, based on the present data.