Cheetahs Originated in North America, Suffered two Population Bottlenecks

The cheetah (Acinonyx jubatus) is now at home on the African plains, but it started a migration 100, 000 years ago from North America towards its current habitat. The research, published in the open access journal Genome Biology, found that the migration from North America was costly for the species, triggering the first major reduction in their gene pool.

The modern African cheetah is found across eastern and southern Africa, but it is highly endangered because of their small free ranging population and inbreeding. Researchers from St. Petersburg State University, Russia, in collaboration with BGI, China and CCF, Namibia, sequenced the genome from a male Namibian cheetah, called 'Chewbaaka', and six other wild cheetahs from Tanzania and Namibia. This gave further insight into the species evolutionary history and the breadth of genome impoverishment, which elevates juvenile mortality, causes extreme abnormalities in sperm development and increases vulnerability to infectious disease outbreaks.

A total of 18 cheetah genes showed damaging mutations and one gene in particular, AKAP4, showed a large number of mutations, which could harm sperm development and may explain why cheetah have a large proportion of defective sperm, and hence their low reproductive success.

The cheetah is descended from a relative of American pumas and their fossil record extends across the Americas, Europe and Asia. The species has suffered two population bottlenecks - an event whereby the population is rapidly reduced due to environmental factors.

The first of these took place 100, 000 years ago, around the late Pleistocene - a geological period shaped by repeated glaciations, when cheetahs started to move towards Asia across the Beringian landbridge and then travelled south to Africa. This migration was punctuated with dwindling populations and limited gene flow due to the individuals' own vast territory boundaries, measuring 300-800 square miles, thereby increasing incestuous mating.

The second bottleneck around 10- 12, 000 years ago, further reduced numbers, leading to further loss of endemic variability observed in modern cheetahs.

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Cougars Survived the Beginning Holocene Megafaunal Extinction due to Dietary Generalism

Cougars may have survived the mass extinction that took place about 12,000 years ago because they were not particular about what they ate, unlike their more finicky cousins—the saber-tooth cat and American lion. Both perished along with the woolly mammoth and many of the other supersized mammals that walked the Earth during the late Pleistocene.

That is the conclusion of a new analysis of the microscopic wear marks on the teeth of cougars, saber-tooth cats and American lions described in the April 23 issue of the journal Biology Letters.

"Before the Late Pleistocene extinction six species of large cats roamed the plains and forests of North America. Only two – the cougar and jaguar – survived. The goal of our study was to examine the possibility that dietary factors can explain the cougar's survival," said Larisa R.G. DeSantis, assistant professor of earth and environmental sciences at Vanderbilt University, who co-authored the study with Ryan Haupt at the University of Wyoming.

For their investigation, DeSantis and Haupt employed a new technique called dental microwear texture analysis. DMTA uses a confocal microscope to produce a three-dimensional image of the surface of a tooth. The image is then analyzed for microscopic wear patterns. The analysis of the teeth of modern carnivores, including hyenas, cheetahs and lions has established that the meals an animal consumes during the last few weeks of its life leave telltale marks. Chowing down on red meat, for example, produces small parallel scratches while chomping on bones adds larger, deeper pits.

The researchers analyzed the teeth of 50 fossil and modern cougars, and compared them with the teeth of saber-tooth cats and American lions excavated from the La Brea Tar Pits in Los Angeles and the teeth of modern African carnivores including cheetahs, lions and hyenas.

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