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

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 constitut...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences
Main Authors: Lindqvist, Charlotte, Schuster, Stephan C., Sun, Yazhou, Talbot, Sandra L., Qi, Ji, Ratan, Aakrosh, Tomsho, Lynn P., Kasson, Lindsay, Zeyl, Eve, Aars, Jon, Miller, Webb, Ingólfsson, Ólafur, Bachmann, Lutz, Wiig, Øystein
Format: Text
Language:English
Published: National Academy of Sciences 2010
Subjects:
Biological Sciences
Arctic
Archipelago
Climate change
Kodiak
Sea ice
Alaska
Online Access:http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2841953
http://www.ncbi.nlm.nih.gov/pubmed/20194737
https://doi.org/10.1073/pnas.0914266107
Description
Summary: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.

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