Three Sharks, Three Fates: The Genetic Divide Of Great Whites

For an animal who - to our current knowledge - shows no parental care, a surprising family drama is unfolding in the world of sharks. Arguably the most iconic of the species, new research shows that the great white shark ( Carcharodon carcharias ) is not the singular global entity we once believed. Instead, it’s a tale of three long-lost cousins, and each lineage is facing its own struggle for survival.

The groundbreaking study published in Current Biology has revealed that the fierce predators are actually divided into three distinct genetic lineages that rarely mix when it comes to producing offspring. Using advanced genomic techniques, researchers at the University of Aberdeen in collaboration with an international team, analyzed DNA from 89 white sharks that were captured across their extensive range (including from the Mediterranean down to Australia). What they discovered was a species divided by ancient events and contemporary ocean currents, explains Dr.



Catherine Jones, the lead researcher from the University of Aberdeen: “At the end of the Penultimate Ice Age – between 100,000 to 200,000 years ago – white shark populations appear to have divided into three discrete lineages which seldom interbreed.” This ancient division, she says, has persisted into the present day, with modern ocean currents serving as barriers that prevent these lineages from mixing. Today, the lineages are located in the North Atlantic and Mediterranean, the North Pacific, and the southern Indo-Pacific.

“Successful conservation requires recognition of management units, but this has been unavailable for white sharks, which were suspected to exist as a single global population,” says Professor Les Noble of Nord University in Norway, who also holds an honorary position at the University of Aberdeen. The study identified only a single shark that appeared to be a hybrid between two lineages, suggesting that while some interbreeding may occur, it is exceedingly rare. This genetic isolation implies that if one population were to vanish, it couldn’t be replenished by sharks from other regions.

Great white sharks are already classified as Vulnerable on the IUCN Red List of Threatened Species, with global populations having plummeted in recent decades. With this recent publication, we now understand that each regional population is even more vulnerable than previously thought. “It has long been considered that sharks lost from one area would be compensated for with the movement and matings of sharks from other locations.

Our findings suggest this is clearly unlikely and this, together with bycatch fishing, depletion of their food reserves, pollution, and poaching, could put this iconic apex predator in real danger of extinction,” Jones points out. Their fearsome reputation often overshadows their vulnerability. Although sharks outlasted the dinosaurs and countless other ancient animals, these magnificent predators may be swimming towards the end of their evolutionary road.

The triple threat of genetic isolation, human activity, and a changing climate may just be too much. “The lack of interbreeding suggests offspring from cross lineage matings may not be viable,” explains Professor Galice Hoarau of Nord University, who warns of a potential “genetic trap” on the horizon. “Should recent forecasts of changes in strength and direction of major ocean currents over the next 50 years be accurate, breakdown of these geographic boundaries between lineages may allow more unproductive matings, further endangering white shark populations and the diversity, health and productivity of ocean ecosystems.

” The team agrees that although genomics is often neglected in assessments of biodiversity and conservation efforts, “the clear resolution it provides can help focus scientifically informed future global management decisions for the white shark.” It might not be too late to protect not just one iconic animal..

. but three. (Well, sort of.

).