Polar Bears evolved recently
A rare, old polar bear fossil discovered in Norway in 2004 is to obtain a wealth of essential information about the age and evolutionary origin of the species whose future is now seen as synonymous with the devastation caused by climate change.
An article in the current edition of the Proceedings of the National Academy of Sciences by researchers at Penn State University, the University of Buffalo, the University of Oslo, and other institutions is filling key pieces of the evolutionary history of the bears polar and brown bears, including their response to past climate changes.
“Our results confirm that the polar bear is a species evolutionarily young people separated from brown bears about 150,000 years ago and has evolved very rapidly during the late Pleistocene, perhaps adjusting the opening of new habitats and food sources in response to climate change, just before the last interglacial period, “says Charlotte Lindqvist, Ph.D., research assistant professor in the Department of Biological Sciences at UB and lead author on the paper, Stephan C. Schuster at Pennsylvania State Center for Comparative Genomics and Bioinformatics.
“Very few polar bear fossils have been found, leading to a wide range of estimates of when and how polar bears evolved,” said Oystein Wiig, polar bear expert and co-author at the University of Oslo, Historical Museum Natural. “Because the polar bears live in ice, their dead remains fall to the bottom of the ocean or get rescued. They are not deposited in sediments, like other mammals.” But in 2004, an Icelandic geologist found a rare and well preserved, from 110,000 to-130 ,000-year-old jaw and canine tooth fossils in the Svalbard archipelago of Norway. This sample was later sent for analysis Wiig.
Lindqvist, who was working at the Oslo Natural History Museum as a postdoc, extracted DNA from the sample after drilling into the bone and tooth powder for analysis. When he came to BU in 2008, obtained tissue samples from modern polar bears and grizzlies and started discussions on the New York UB Center of Excellence in Bioinformatics and Life Sciences after started collaborating with Schuster at Penn State.
This work resulted in the complete mitochondrial genome sequence of fossils, the scientists used this information to develop mitochondrial sequence bears and others to construct phylogenies show that the polar bear evolved within the ancient lineage of brown bears. “From the Admiralty of brown bears in Alaska, Baranof, and Chichagof Islands are the closest relatives of polar bears, it is essential to include in our study to more precisely determine the date when the polar bears appeared as a distinct species, Lindqvist said. “The fact that our old polar bear is almost directly at the point of division between this unique group of brown bears and polar bears, that is, near its most recent common ancestor of both species is very interesting. It is a ideal opportunity to resolve the ultimate time of origin of the polar bear. ”
“This is by far the oldest in the mammalian mitochondrial genome to be sequenced,” says Schuster. “It’s almost twice the age of the oldest mammoth genome has, to date, has been sequenced.”
The mitochondrial genome refers to all the DNA in the mitochondria, the energy production component of most eukaryotic cells (complex). Lindqvist, explains that the ancient DNA studies have tended to focus on the mitochondrial genome, and which may reflect features useful for analysis of trends and allows DNA to be retrieved from ancient samples easier.
To conduct its analysis, the researchers used a variety of techniques, including isotope analysis, high-performance genome sequencing, bioinformatics and phylogenetic analysis, which traces the evolutionary relationships among species. While their data show how adaptive polar bears have been historically, scientists warn against the assumption that polar bears, therefore, also be able to adapt to current and future changes in the Arctic.
“We found that polar bears survived the warm interglacial period, which was generally warmer than today,” Lindqvist said, “but it is possible that Svalbard might have served as refuge for bears, providing a habitat where they can survive . However, climate change may now be occurring at a pace so fast that we do not know whether polar bears will be able to keep up. “Ultimately, he says, the polar bear species may prove less adaptable. “The polar bear may be evolutionarily constrained because it is now highly specialized morphological, physiological and behavioral well adapted to life on the edge of the Arctic ice, subsisting on a few species of seals,” she says.
Lindqvist and Schuster are seriously considering working in the nuclear genome sequencing of the old polar bear, the work they hope to unveil more about the evolution of the polar bear.
The work was funded by the Gordon and Betty Moore Foundation, the UB College of Arts and Sciences, the Museum of Natural History, University of Oslo and the U.S. USGS Alaska Science Center.
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