Supporting Data for: Ocean-wide conservation genomics of blue whales suggest new Northern Hemisphere subspecies

The blue whale is an endangered and globally distributed species of baleen
whale with multiple described subspecies assignments, including the
morphologically and molecularly distinct pygmy blue whale, among others.
North Atlantic and North Pacific populations, however, are currently
regarded as a single subspecies despite being separated by continental
land masses and differences in their acoustic communication. To determine
the degree of isolation among the Northern Hemisphere populations,
fourteen North Pacific and six Western Australian blue whale nuclear and
mitochondrial genomes were sequenced and analyzed combinedly with eleven
publicly available North Atlantic blue whale genomes. This allowed to
contrast the genetic differentiation and genetic exchange among Northern
Hemisphere populations to the Western Australian pygmy blue whale
subspecies. Population genomic analyses revealed distinctly differentiated
clusters and limited exchange among all three populations, indicating a
high degree of isolation. Nevertheless, the genomic and mitogenomic
distances between all blue whale populations, including the Western
Australian pygmy blue whale, are low when compared to other
inter-subspecies distances in cetaceans. Given that the pygmy blue whale
is an already recognized subspecies and further supported by previously
reported acoustic differences, a proposal is made to treat the two
Northern Hemisphere populations equally as subspecies,
namely Balaenoptera musculus musculus (North Atlantic blue whale)
and Balaenoptera musculus sulfureus (North Pacific blue whale).
Furthermore, a first molecular vitality assessment of all three
populations found a generally high genomic diversity among blue whales but
also a lack of rare alleles, non-neutral evolution and substantially
increased effects of inbreeding. This suggests a substantial anthropogenic
impact on the genotypes of blue whales and calls for careful monitoring in
future conservation plans.