Population structure of the Atlantic angel shark (Squatina dumeril) in United States waters of the western North Atlantic Ocean

While dorsal-ventrally compressed chondrichthyans are among the most imperiled fishes in the world, there is still limited knowledge of the biology of many of these species, even in well-studied ocean basins. In the western North Atlantic Ocean, the population structure of the Atlantic angel shark (Squatina dumeril) is not fully understood; therefore, the portioning of genetic variation was assessed among individuals caught along the east coast of the United States (Atlantic) and on the northern Gulf of Mexico (Gulf) using reduced representation genomics and mitochondrial sequencing. Three distinct groups were delineated with nuclear data, the Atlantic, the eastern Gulf, and the western Gulf, along boundaries described by previous research. Mitochondrial data only resolved two groups, with the western Gulf separated from the eastern Gulf and Atlantic combined. Demographic modeling suggested that the Atlantic population separated from a single Gulf population which subsequently split into eastern and western populations. Additionally, there was evidence that adjacent populations experienced gene flow after splitting, which may explain the incongruence between results based on nuclear and mtCR data. Correlations between environmental variables and allele frequencies at 873 loci indicated potential local adaptation. Therefore, the preservation of all three groups is necessary for the conservation of long-term adaptive variation important for species persistence.