Data from: Genomic signatures of population bottleneck and recovery in Northwest Atlantic pinnipeds

Population increases over the past several decades provide natural
settings in which to study the evolutionary processes that occur during
bottleneck, growth, and spatial expansion. We used parallel natural
experiments of historical decline and subsequent recovery in two sympatric
pinniped species in the Northwest Atlantic, the gray seal (Halichoerus
grypus atlantica) and harbor seal (Phoca vitulina vitulina), to study the
impact of recent demographic change in genomic diversity. Using
restriction site‐associated DNA sequencing, we assessed genomic diversity
at over 8,700 polymorphic gray seal loci and 3,700 polymorphic harbor seal
loci in samples from multiple cohorts collected throughout recovery over
the past half‐century. Despite significant differences in the degree of
genetic diversity assessed in the two species, we found signatures of
historical bottlenecks in the contemporary genomes of both gray and harbor
seals. We evaluated temporal trends in diversity across cohorts, as well
as compared samples from sites at both the center and edge of a recent
gray seal range expansion, but found no significant change in genomewide
diversity following recovery. We did, however, find that the variance and
degree of allele frequency change measured over the past several decades
were significantly different from neutral expectations of drift under
population growth. These two cases of well‐described demographic history
provide opportunities for critical evaluation of current approaches to
simulating and understanding the genetic effects of historical demographic
change in natural populations.