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Complete mitochondrial genome of a Pleistocene jawbone unveils the origin of polar bear

PNAS

By:
, , , , , , , , , , , , ,
DOI: 10.1073/pnas.0914266107

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Abstract

The polar bear has become the flagship species in the climate-change discussion. However, little is known about how past climate impacted its evolution and persistence, given an extremely poor fossil record. Although it is undisputed from analyses of mitochondrial (mt) DNA that polar bears constitute a lineage within the genetic diversity of brown bears, timing estimates of their divergence have differed considerably. Using next-generation sequencing technology, we have generated a complete, high-quality mt genome from a stratigraphically validated 130,000- to 110,000-year-old polar bear jawbone. In addition, six mt genomes were generated of extant polar bears from Alaska and brown bears from the Admiralty and Baranof islands of the Alexander Archipelago of southeastern Alaska and Kodiak Island. We show that the phylogenetic position of the ancient polar bear lies almost directly at the branching point between polar bears and brown bears, elucidating a unique morphologically and molecularly documented fossil link between living mammal species. Molecular dating and stable isotope analyses also show that by very early in their evolutionary history, polar bears were already inhabitants of the Artic sea ice and had adapted very rapidly to their current and unique ecology at the top of the Arctic marine food chain. As such, polar bears provide an excellent example of evolutionary opportunism within a widespread mammalian lineage.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Complete mitochondrial genome of a Pleistocene jawbone unveils the origin of polar bear
Series title:
PNAS
DOI:
10.1073/pnas.0914266107
Volume
107
Issue:
11
Year Published:
2010
Language:
English
Publisher:
National Academy of Sciences
Publisher location:
Baltimore, MD
Contributing office(s):
Alaska Science Center
Description:
5 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
5053
Last page:
5057
Number of Pages:
5