Posted by: The ocean update | May 6, 2015

Lack of diversity in pygmy blue whales not due to man-made cause

Pygmy blue whale. Credit: © Research team (Attard et. al)

Pygmy blue whale. Credit: © Research team (Attard et. al)

May 6th, 2015 (Bob Yirka). A team of researchers working in Australia has found via DNA analysis, that the lack of genetic diversity in pygmy blue whales is due to natural causes, not because of whaling. In their paper published in the journal Biology Letters, the researchers, affiliated with a variety of institutions in Australia, describe their study of the whales and why what they learned may help save them.

Pygmy blue whales are a subspecies of blue whales and contrary to their name, are not really all that small. They average 24 meters in length compared to their bigger cousins, which average 28 to 30 meters in length.

For many years marine biologists have assumed that the lack of genetic diversity found in pygmy blue whales living around the shores of Australia, was due to their numbers being cut due to whaling. Now it appears that is not the case. In this new effort, the researchers sought to better understand the history of the whales and how they wound up with so little diversity. To learn more, they obtained DNA samples from several specimens and then studied patterns of genetic mutations—that allowed them to see that the whales had all come from just a few individuals, a “founder group,” beginning around 20,000 years ago. After comparing the pygmy whale DNA with other blue whales living in other parts of the world, the team was able to ascertain that they had gotten their start as Antarctic blue whales.

The researchers note that 20,000 years ago, the Earth was experiencing peak glaciation, which allowed blue whales (currently the largest animal on the planet) to travel to other places, one of which was, apparently Australia. But then the glaciers retreated, leaving those that had migrated to adapt to their new environment—they evolved into the pygmy blue whales that exist today.

That is good news for the species, because it means their lack of diversity is not due to whaling, (which did reduce their numbers dramatically, along with other blue whales)—it is because they are still so new of a species. Also because they are now a protected species, the researchers believe that if they can mitigate other threats, such as different sorts of human pollution, the whales have a good chance of returning to their pre-whaling population.

Pygmy blue whale. Credit: © Research team (Attard et. al)

Pygmy blue whale. Credit: © Research team (Attard et. al)

Citation : Low genetic diversity in pygmy blue whales is due to climate-induced diversification rather than anthropogenic impactsBiology LettersDOI : 10.1098/rsbl.2014.1037

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