August 9, 2005
DNA Traces Evolution of Extinct Sabertooths and the American Cheetah-like Cat
By performing sequence analysis of ancient DNA, a team of researchers has obtained data that help clarify our view of the evolutionary relationships shared by the large predatory cats that once roamed the prehistoric New World.
The work is reported in the August 9 issue of Current Biology by Ross Barnett of the University of Oxford and a team of researchers from Britain, Canada, the United States, Sweden, and Australia.Toward the end of the last Ice Age, around 13,000 years ago, North and South America were home to a variety of large cats such as the sabertooths (Smilodon and Homotherium) and other now-extinct species known as the American lion-like cat (Panthera atrox) and cheetah-like cat (Miracinonyx trumani). Of these big cats, only the puma (Puma concolor) and jaguar (Panthera onca) survive in the Americas today.
The evolutionary history of the extinct American cats has been closely studied by palaeontologists, but it has been difficult to determine the exact relationships of several groups. In the work reported this week, researchers created an updated family tree for the ancient cats by comparing ancient DNA extracted from the preserved bones of the two sabertooths (a Smilodon specimen from Patagonia and a Homotherium specimen from the Yukon region) and the American cheetah-like cat (a Miracinonyx specimen from the state of Wyoming) with DNA from modern felid (cat-family) and carnivore species. The analysis shows that the sabertooth cats were a sister group to the modern cats--that is, they diverged early on from the ancestors of modern cats and are not closely related to any living felid species.
The phylogenetic tree drawn from the new data also shows that the American cheetah-like cat is genetically most closely related to the puma, rather than to the true African cheetah (Acinonyx jubatus). Miracinonyx and the true cheetah Acinonyx show remarkable morphological similarity, including elongated limbs and enlarged nares, but the genetic data indicate that this similarity is in fact a marvellous example of evolutionary parallelism, the development of similar body plans in response to similar ecological pressures. In light of the new DNA data and fossil information from other studies, it appears likely that a puma-like ancestor that migrated to the New World may have given rise to Miracinonyx and ancestral Puma a few million years ago, around the time that the North American prairie is thought to have undergone expansion.
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