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Evolutionary History of Saber-Toothed Cats Based on Ancient Mitogenomics; Paijmans et al., Current Biology (2017), https://doi.org/10.1016/j.cub.2017.09.033
Topic Started: Oct 21 2017, 02:50 PM (450 Views)
Taipan
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Ancient DNA offers new view on saber-toothed cats' past

Date: October 19, 2017
Source: Cell Press

Posted Image
This is a photograph of a homotherium fossil recovered from the North Sea.
Credit: Natural History Museum Rotterdam

Researchers who've analyzed the complete mitochondrial genomes from ancient samples representing two species of saber-toothed cats have a new take on the animals' history over the last 50,000 years. The data suggest that the saber-toothed cats shared a common ancestor with all living cat-like species about 20 million years ago. The two saber-toothed cat species under study diverged from each other about 18 million years ago.

"It's quite crazy that, in terms of their mitochondrial DNA, these two saber-toothed cats are more distant from each other than tigers are from house cats," says Johanna Paijmans at the University of Potsdam in Germany.

Paijmans and colleagues reconstructed the mitochondrial genomes from ancient-DNA samples representing three Homotherium from Europe and North America and one Smilodon specimen from South America. One of the Homotherium specimens under investigation is a unique fossil: a 28,000-year-old mandible recovered from the North Sea.

"This find was so special because Homotherium is generally believed to have gone extinct in Europe around 300,000 years ago, so [this specimen is] over 200,000 years younger than the next-to-youngest Homotherium find in Europe," Paijmans explains.

The new DNA evidence confirmed that this surprisingly young specimen did indeed belong to a Homotherium. The discovery suggests that the saber-toothed cats continued to live in Europe much more recently than scientists previously thought.

"When the first anatomically modern humans migrated to Europe, there may have been a saber-toothed cat waiting for them," Paijmans says.

The finding raises new questions about how and why the saber-toothed cats went extinct. Paijmans says they are now interested in studying DNA from other samples of saber-toothed cats. Although it will be technically challenging, they also hope to recover and analyze DNA from much older Homotherium specimens.

This project received funding from the European Research Council, the European Union's Seventh Framework Programme for research, technological development, and demonstration and the Lundbeck Foundation.

Story Source: Cell Press. "Ancient DNA offers new view on saber-toothed cats' past." ScienceDaily. www.sciencedaily.com/releases/2017/10/171019143018.htm (accessed October 20, 2017).




Journal Reference:
Johanna L.A. Paijmans, Ross Barnett, M. Thomas P. Gilbert, M. Lisandra Zepeda-Mendoza, Jelle W.F. Reumer, John de Vos, Grant Zazula, Doris Nagel, Gennady F. Baryshnikov, Jennifer A. Leonard, Nadin Rohland, Michael V. Westbury, Axel Barlow, Michael Hofreiter. Evolutionary History of Saber-Toothed Cats Based on Ancient Mitogenomics. Current Biology, 2017; DOI: 10.1016/j.cub.2017.09.033

Posted Image
Calibrated Phylogeny for Smilodon and Homotherium
Time-calibrated mitochondrial phylogeny of the Felidae, including the saber-toothed cat Smilodon and scimitar-toothed Homotherium. Node support is indicated by Bayesian posterior probabilities (see Figure S2 for RAxML phylogeny and bootstrap values). Calibrated nodes are indicated with a star (see also Table 2). Blue node bars indicate the 95% credibility interval of divergence times. The lower axis shows millions of years. Homotherium artwork was provided by Binia De Cahsan. The image of the mandible is adapted from [4]. See also Figures S1 and S2.

Highlights
•We present the first near-complete mitochondrial genomes from saber-toothed cats
•Smilodon and Homotherium are estimated to have diverged ca. 18 million years ago
•We find limited genetic divergence between American and European Homotherium
•Late Pleistocene Homotherium should be considered a single species: H. latidens

Summary
Saber-toothed cats (Machairodontinae) are among the most widely recognized representatives of the now largely extinct Pleistocene megafauna. However, many aspects of their ecology, evolution, and extinction remain uncertain. Although ancient-DNA studies have led to huge advances in our knowledge of these aspects of many other megafauna species (e.g., mammoths and cave bears), relatively few ancient-DNA studies have focused on saber-toothed cats [1, 2, 3], and they have been restricted to short fragments of mitochondrial DNA. Here we investigate the evolutionary history of two lineages of saber-toothed cats (Smilodon and Homotherium) in relation to living carnivores and find that the Machairodontinae form a well-supported clade that is distinct from all living felids. We present partial mitochondrial genomes from one S. populator sample and three Homotherium sp. samples, including the only Late Pleistocene Homotherium sample from Eurasia [4]. We confirm the identification of the unique Late Pleistocene European fossil through ancient-DNA analyses, thus strengthening the evidence that Homotherium occurred in Europe over 200,000 years later than previously believed. This in turn forces a re-evaluation of its demography and extinction dynamics. Within the Machairodontinae, we find a deep divergence between Smilodon and Homotherium (∼18 million years) but limited diversity between the American and European Homotherium specimens. The genetic data support the hypothesis that all Late Pleistocene (or post-Villafrancian) Homotherium should be considered a single species, H. latidens, which was previously proposed based on morphological data [5, 6].
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Edited by Taipan, Oct 21 2017, 02:52 PM.
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