Low Genetic Diversity Is Usually A Death Sentence – But Not For Narwhals

Source: Science/Jake Buehler

Photo: Mads Peter Heide-Jørgensen/NOAA

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Low genetic diversity—often brought on by a mass die-off or inbreeding—has been considered a death knell for species from heath hens to Tasmanian tigers. Without lots of genetic material to reshuffle, future generations are less able to adapt to changing environmental conditions. Now, a new genetic analysis of narwhals is turning that notion on its head: Despite low genetic diversity, these “unicorns” of the ocean seem to be doing just fine.

Narwhals, medium-size whales that live in the Arctic, are known for some genetic quirks. After multiple studies uncovered low genetic diversity in several narwhal genes, a team of researchers decided to analyze the whale’s entire genome. Using DNA from the frozen liver tissue of a narwhal found near Greenland, they calculated the genetic variation of the species and estimated the population size of narwhals into the deep past.

Their results reveal a profound lack of diversity across the narwhal’s genome, they report today in iScience. Compared with 14 other mammal species, narwhals were far less genetically diverse.

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Photo: Mads Peter Heide-Jørgensen/NOAA

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