The United Nations declared 2010 to be the International Year of Biodiversity and invited the world to take action to safeguard the variety of life on earth. Unfortunately, though, it is seldom completely clear what should be safeguarded. An example is provided by the cheetah, which conventional wisdom tells us does not vary much throughout its wide (if shrinking) range.
Recent work in the group of Pamela Burger of the University of Veterinary Medicine, Vienna challenges this view and shows that the cheetahs in Northern-East Africa and those in Asia differ markedly from the populations in Southern Africa. The results are published in the current issue of the journal Molecular Ecology and have profound and far-reaching implications for the conservation of the species.
Historically, cheetahs were widespread throughout Africa and much of Southwest Asia, ranging through Kazakhstan and the entire Indian peninsula. The present situation is very different and the remaining animals are concentrated in certain areas in southern and eastern Africa. Very few cheetahs now exist in the wild in Asia, where the species is confined to small areas in Iran. It has long been believed that cheetahs show relatively low levels of genetic variation, although previous studies have not examined the entire geographic range. Pauline Charruau and Pamela Burger of the Institute of Population Genetics at the University of Veterinary Medicine, Vienna have collaborated with groups in a number of other countries -- Portugal, Germany, the United States, Iran, the United Arab Emirates, France and South Africa -- to investigate a large number of cheetah DNA samples. The researchers even included in their study DNA that they extracted from bones found in mediaeval sites in north-west Iran. By means of sophisticated statistical methods to compare the sequences of certain pieces of the DNA, the scientists were able to gain a far more complete picture of the range of diversity in the species.
The results are dramatic. Cheetahs in Northern-East Africa (in Sudan, Somalia, Ethiopia and Djibouti) differ significantly from the animals further south. Furthermore, the few cheetahs remaining in Iran are markedly distinct. It seems likely that the populations separated about 30,000 to 70,000 years ago and are thus more ancient than previously suspected. The cheetahs in Southern and Eastern Africa are known to represent two closely related subspecies but Burger's work reveals that the other subspecies in Northern-East Africa and in Asia represent older and highly distinct lineages.
The populations in sub-Saharan Africa are relatively secure but this is unfortunately not the case for the subspecies in Asia. And because Iranian cheetahs are the last representatives of the Asiatic subspecies and are so dissimilar from their African relatives, their conservation is a priority. There are only about 100 individuals left in Iran, possibly even fewer, so urgent action is needed to ensure the survival of this distinct form. Together with the United Nations Development Programme, the Iranian Department of the Environment (which cooperated on the paper) has established a comprehensive programme (CACP) that makes conservation of the Asiatic cheetah a national priority. Nevertheless, "We are running out of time to save the Asiatic cheetah," says Alireza Jourabchian, Director of the CACP in Iran. "We have been successful in stabilizing numbers in Iran but we still have a long way to go before we can consider this unique sub-species secure. We are hopeful these new findings will bring even greater attention to its plight."
A strategy that has been frequently employed to conserve endangered species is to capture individuals in an area where the animals are common and release them at sites where they are rare. Along these lines, the critically low Iranian population could be supplemented with animals taken from Southern and Northern-East Africa but the findings from Burger's group argue strongly against such a course. As Burger says, "it would promote interbreeding between the forms and thereby dilute the genetic distinctiveness of the Asiatic cheetahs, which is presumably related to the habitats and prey available in Asia."
- P. Charruau, C. Fernandes, P. Orozco-Terwengel, J. Peters, L. Hunter, H. Ziaie, A. Jourabchian, H. Jowkar, G. Schaller, S. Ostrowski, P. Vercammen, T. Grange, C. Schlötterer, A. Kotze, E.-M. Geigl, C. Walzer, P. A. Burger. Phylogeography, genetic structure and population divergence time of cheetahs in Africa and Asia: evidence for long-term geographic isolates. Molecular Ecology, 2011; DOI: 10.1111/j.1365-294X.2010.04986.x
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