Data from: What influences the worldwide genetic structure of sperm whales (Physeter macrocephalus)?

The interplay of natural selection and genetic drift, influenced by
geographic isolation, mating systems and population size, determines
patterns of genetic diversity within species. The sperm whale provides an
interesting example of a long-lived species with few geographic barriers
to dispersal. Worldwide mtDNA diversity is relatively low, but highly
structured among geographic regions and social groups, attributed to
female philopatry. However, it is unclear whether this female philopatry
is due to geographic regions or social groups, or how this might vary on a
worldwide scale. To answer these questions, we combined mtDNA information
for 1091 previously published samples with 542 newly obtained DNA profiles
(394-bp mtDNA, sex, 13 microsatellites) including the previously unsampled
Indian Ocean, and social group information for 541 individuals. We found
low mtDNA diversity (π = 0.430%) reflecting an expansion event <80
000 years bp, but strong differentiation by ocean, among regions within
some oceans, and among social groups. In comparison, microsatellite
differentiation was low at all levels, presumably due to male-mediated
gene flow. A hierarchical amova showed that regions were important for
explaining mtDNA variance in the Indian Ocean, but not Pacific, with
social group sampling in the Atlantic too limited to include in analyses.
Social groups were important in partitioning mtDNA and microsatellite
variance within both oceans. Therefore, both geographic philopatry and
social philopatry influence genetic structure in the sperm whale, but
their relative importance differs by sex and ocean, reflecting breeding
behaviour, geographic features and perhaps a more recent origin of sperm
whales in the Pacific. By investigating the interplay of evolutionary
forces operating at different temporal and geographic scales, we show that
sperm whales are perhaps a unique example of a worldwide population
expansion followed by rapid assortment due to female social organization.