Mitchell Kieren J, Bray Sarah C, Bover Pere, Soibelzon Leopoldo, Schubert Blaine W, Prevosti Francisco, Prieto Alfredo, Martin Fabiana, Austin Jeremy J, Cooper Alan
Australian Centre for Ancient DNA, School of Biological Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia
Australian Centre for Ancient DNA, School of Biological Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia Acute Leukaemia Laboratory, Centre for Cancer Biology, University of South Australia, Adelaide, South Australia 5000, Australia.
Biol Lett. 2016 Apr;12(4). doi: 10.1098/rsbl.2016.0062.
The Tremarctinae are a subfamily of bears endemic to the New World, including two of the largest terrestrial mammalian carnivores that have ever lived: the giant, short-faced bears Arctodus simus from North America and Arctotherium angustidens from South America (greater than or equal to 1000 kg). Arctotherium angustidens became extinct during the Early Pleistocene, whereas Arctodus simus went extinct at the very end of the Pleistocene. The only living tremarctine is the spectacled bear (Tremarctos ornatus), a largely herbivorous bear that is today only found in South America. The relationships among the spectacled bears (Tremarctos), South American short-faced bears (Arctotherium) and North American short-faced bears (Arctodus) remain uncertain. In this study, we sequenced a mitochondrial genome from an Arctotherium femur preserved in a Chilean cave. Our molecular phylogenetic analyses revealed that the South American short-faced bears were more closely related to the extant South American spectacled bear than to the North American short-faced bears. This result suggests striking convergent evolution of giant forms in the two groups of short-faced bears (Arctodus and Arctotherium), potentially as an adaptation to dominate competition for megafaunal carcasses.
眼镜熊亚科是新世界特有的熊亚科，包括有史以来最大的两种陆生哺乳动物食肉动物：来自北美的巨型短面熊北美巨型短面熊（Arctodus simus）和来自南美的窄齿短面熊（Arctotherium angustidens）（体重≥1000千克）。窄齿短面熊在早更新世灭绝，而北美巨型短面熊在更新世末期灭绝。唯一现存的眼镜熊亚科动物是眼镜熊（Tremarctos ornatus），一种主要食草的熊，如今仅在南美洲发现。眼镜熊（Tremarctos）、南美短面熊（Arctotherium）和北美短面熊（Arctodus）之间的关系仍不确定。在本研究中，我们对保存在智利一个洞穴中的窄齿短面熊股骨的线粒体基因组进行了测序。我们的分子系统发育分析表明，南美短面熊与现存的南美眼镜熊的亲缘关系比与北美短面熊更近。这一结果表明，两组短面熊（北美巨型短面熊和窄齿短面熊）的巨型形态存在显著的趋同进化，这可能是为了适应在争夺大型动物尸体的竞争中占据主导地位。
