Complete mitochondrial genome of a Pleistocene jawbone unveils the origin of polar bear
Complete mitochondrial genome of a Pleistocene jawbone unveils the origin of polar bear
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DOI：
10.1073/pnas.0914266107
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发表时间：
2010-03-16
影响因子：
11.1
通讯作者：
Wiig, Oystein
中科院分区：
文献类型：
--
作者：
Lindqvist, Charlotte;Schuster, Stephan C.;Wiig, Oystein
北极熊已经成为气候变化讨论中的旗舰物种。然而，由于化石记录极其贫乏，人们对过去的气候如何影响其进化和持久性知之甚少。虽然从线粒体（mt）DNA的分析来看，北极熊在棕熊的遗传多样性中构成了一个谱系，这是无可争议的，但对它们分歧的时间估计有很大的不同。利用下一代测序技术，我们从一个经过地层学验证的13万到11万年前的北极熊颌骨中获得了一个完整的、高质量的mt基因组。此外，六个mt基因组产生的现存的北极熊从阿拉斯加和棕熊从海军部和巴拉诺夫群岛的亚历山大群岛的东南阿拉斯加和科迪亚克岛。我们发现，古代北极熊的系统发育位置几乎直接位于北极熊和棕熊之间的分支点，阐明了一个独特的形态和分子记录的活哺乳动物物种之间的化石联系。分子年代测定和稳定同位素分析还表明，在北极熊进化史的早期，北极熊就已经是北极海冰的居民，并迅速适应了北极海洋食物链顶端目前独特的生态环境。因此，北极熊提供了一个很好的例子，在广泛的哺乳动物血统的进化机会主义。
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.