Genome analysis reveals three distinct lineages of the cosmopolitan white shark.

The white shark (Carcharodon carcharias) (Linnaeus, 1758), an iconic apex predator occurring in all oceans, ^{1 , 2} is classified as Vulnerable globally ³ -with global abundance having dropped to 63% of 1970s estimates, ⁴ -and as Critically Endangered in Europe. ⁵ Identification of evolutionary significant units and their management are crucial for conservation, ⁶ especially as the white shark is facing various but often region-specific anthropogenic threats. ^{7 , 8 , 9 , 10 , 11} Assessing connectivity in a cosmopolitan marine species requires worldwide sampling and high-resolution genetic markers. ¹² Both are lacking for the white shark, with studies to date typified by numerous but geographically limited sampling, and analyses relying largely on relatively small numbers of nuclear microsatellites, ^{13 , 14 , 15 , 16 , 17 , 18 , 19} which can be plagued by various genotyping artefacts and thus require cautious interpretation. ²⁰ Sequencing and computational advances are finally allowing genomes ^{21 , 22 , 23} to be leveraged into population studies, ^{24 , 25 , 26 , 27} with datasets comprising thousands of single-nucleotide polymorphisms (SNPs). Here, combining target gene capture (TGC) ²⁸ sequencing (89 individuals, 4,000 SNPs) and whole-genome re-sequencing (17 individuals, 391,000 SNPs) with worldwide sampling across most of the distributional range, we identify three genetically distinct allopatric lineages (North Atlantic, Indo-Pacific, and North Pacific). These diverged 100,000-200,000 years ago during the Penultimate Glaciation, when low sea levels, different ocean currents, and water temperatures produced significant biogeographic barriers. Our results show that without high-resolution genomic analyses of samples representative of a species' range, ¹² the true extent of diversity, presence of past and contemporary barriers to gene flow, subsequent speciation, and local evolutionary events will remain enigmatic.
Competing Interests: Declaration of interests The authors declare no competing interests.
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