Data from: Hierarchical population structure and habitat differences in a highly mobile marine species: the Atlantic spotted dolphin

Recent molecular studies have shown that highly mobile species with
continuous distributions can exhibit fine-scale population structure. In
this context, we assessed genetic structure within a marine species with
high dispersal potential, the Atlantic spotted dolphin (Stenella
frontalis). Using 19 microsatellite loci and mitochondrial control region
sequences, population structure was investigated in the western North
Atlantic, the Gulf of Mexico and the Azores Islands. Analyses of the
microsatellite data identified four distinct genetic clusters, which were
supported by the control region sequences. The highest level of divergence
was seen between two clusters corresponding to previously-described
morphotypes that inhabit oceanic and shelf waters. The combined
morphological and genetic evidence suggests these two lineages are on
distinct evolutionary trajectories and could be considered distinct
subspecies despite their parapatry. Further analysis of the continental
shelf cluster resulted in three groups: animals inhabiting shelf waters in
the western North Atlantic, the eastern Gulf of Mexico, and the western
Gulf of Mexico. Analyses of environmental data indicate the four genetic
clusters inhabit distinct habitats in terms of depth and sea surface
temperature. Contemporary dispersal rate estimates suggest all of these
populations should be considered as distinct management units. Conversely,
no significant genetic differentiation was observed between S. frontalis
from offshore waters of the western North Atlantic and the Azores, which
are separated by approximately 4500 km. Overall, the hierarchical
structure observed within the Atlantic spotted dolphin shows that the
biogeography of the species is complex because it is not shaped solely by
geographic distance.