Data from: Genetic and evolutionary divergence of harbor seals (Phoca vitulina) in Iliamna Lake, Alaska

Freshwater populations of typically marine species present unique
opportunities to investigate biodiversity, evolutionary divergence, and
the adaptive potential and niche width of species. A few pinniped species
have populations that reside solely in freshwater. The harbor seals
inhabiting Iliamna Lake, Alaska constitute one such population. Their
remoteness, however, has long hindered scientific inquiry. We used DNA
from seal scat and from tissue samples provided by Indigenous hunters to
screen for mitochondrial DNA and microsatellite variation within Iliamna
Lake and eight regions across the Pacific Ocean. The Iliamna seals: (1)
were substantially and significantly discrete from all other populations (
 Fst-mtDNA= 0.544,   Φst-mtDNA = 0.541,
 Fst-microsatellites = 0.308), (2) formed a discrete genetic
cluster separate from all marine populations (modal ∆k=2, PC1=14.8%), and
had (3) less genetic diversity (Hd, π, Hexp) and (4) higher inbreeding (F)
than marine populations. These findings are both striking and unexpected
revealing that Iliamna seals have likely been on a separate evolutionary
trajectory for some time and may represent a unique evolutionary legacy
for the species. Attention must now be given to the selective processes
driving evolutionary divergence from harbor seals in marine habitats, and
to ensuring the future of the Iliamna seal.