Data from: Contemporary population structure and post-glacial genetic demography in a migratory marine species, the blacknose shark, Carcharhinus acronotus

Patterns of population structure and historical genetic demography of
blacknose sharks in the western North Atlantic Ocean were assessed using
variation in nuclear-encoded microsatellites and sequences of
mitochondrial (mt)DNA. Significant heterogeneity and/or inferred barriers
to gene flow, based on microsatellites and/or mtDNA, revealed the
occurrence of five genetic populations localized to five geographic
regions: the southeastern U.S Atlantic coast, the eastern Gulf of Mexico,
the western Gulf of Mexico, Campeche Bay in the southern Gulf of Mexico,
and the Bahamas. Pairwise estimates of genetic divergence between sharks
in the Bahamas and those in all other localities were more than an order
of magnitude higher than between pairwise comparisons involving the other
localities. Demographic modelling indicated that sharks in all five
regions diverged after the last glacial maximum and, except for the
Bahamas, experienced post-glacial, population expansion. The patterns of
genetic variation also suggest that the southern Gulf of Mexico may have
served as a glacial refuge and source for the expansion. Results of the
study demonstrate that barriers to gene flow and historical genetic
demography contributed to contemporary patterns of population structure in
a coastal migratory species living in an otherwise continuous marine
habitat. The results also indicate that for many marine species, failure
to properly characterize barriers in terms of levels of contemporary gene
flow could in part be due to inferences based solely on equilibrium
assumptions. This could lead to erroneous conclusions regarding levels of
connectivity in species of conservation concern.