Short-finned pilot whales are found over a wide swath of the world's oceans, with habitats in the Indian, and Pacific, and North Atlantic oceans. Despite this wide distribution, the whales have been recognized as a single species—but a recent study has found that two unique subspecies actually exist. The study published June 3, 2019, in Molecular Ecology.
Japanese whalers and scientists have long described two "forms" of short-finned pilot whales with distinct body types—the 'Naisa' form, which live in Southern Japan and have square-shaped heads; and the 'Shiho' form, which lives in northern Japan and have round heads. Yet no prior study had examined the genetic diversity of those whales on a global scale, says Amy Van Cise, a postdoctoral scholar at WHOI and lead author on the study.
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"You can't manage animals globally without understanding their diversity. If you think of a group of animals as a single species, and it turns out they're not, you could wind up accidentally losing an entire subspecies without knowing it," she says.
Van Cise was able to study the entire global population structure of the whales using marine mammal tissue archived at NOAA's Southwest Fisheries Science Center. From it, she identified more than 700 samples taken from short-finned pilot whales, and extracted DNA from each one.
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After analyzing the DNA, Van Cise found that there are actually two distinct subspecies of short-finned pilot whale. Surprisingly, she says, those subspecies aren't separated by any continental barrier, but instead by the vast expanse of the eastern Pacific Ocean.
"You would expect to see a different subspecies of whale in each ocean basin—the Atlantic, Indian, and Pacific. That's pretty common. But what we found was that short-finned pilot whales in...
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