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(05-19-2014, 04:46 PM)'Apollo' Wrote: Increase genetic diversity to save tigers: Study

While Ranthambhore Tiger Reserveis facing the problem of plenty with 60 tigers in 392 sq. km, Sariska spread over 866 sq. km houses just nine tigers after the relocation in 2008. Sariska that had lost all its tigers saw hopes of revival with tigers being brought to the reserve from the Ranthambhore reserve after genetic studies undertaken the first time in the country.

Now, a new research by Stanford scholars shows that increasing genetic diversityamong the 3,000 or so tigers left on the planet is the key to their survival as a species. That research shows that the more gene flow there is among tiger populations, the more genetic diversity is maintained and the higher the chances of species survival become. In fact, it might be possible to maintain tiger populations that preserve about 90 percent of genetic diversity. The research focused on the Indian subcontinent, home to about 65 percent of the world's wild tigers. The scientists found that as populations become more fragmented and the pools of each tiger subspecies shrink, so does genetic diversity. This loss of diversity can lead to lower reproduction rates, faster spread of disease and more cardiac defects, among other problems.

Rachael Bay, a graduate student in biology at Stanford's Hopkins Marine Station and the lead author of the study, said, "Genetic diversity is the basis for adaptation." The researchers used a novel framework, based on a method previously employed to analyze ancient DNA samples, to predict what population size would be necessary to maintain current genetic diversity of tigers into the future. The authors believe this new approach could help in managing populations of other threatened species.

The results showed that for tiger populations to maintain their current genetic diversity 150 years from now, the tiger population would have to expand to about 98,000 individuals if gene flow across species were delayed 25 years. By comparison, the population would need to grow to about 60,000 if gene flow were achieved immediately. Neither of these numbers is realistic, considering the limited size of protected tiger habitat and availability of prey, among other factors, according to the researchers.

"Since genetic variability is the raw material for future evolution, our results suggest that without interbreeding sub-populations of tigers, the genetic future for tigers is not viable," said co-author Uma Ramakrishnan, a former Stanford postdoctoral scholar in biology and current researcher at the National Centre for Biological Sciences in Bangalore, India.

Because migration and interbreeding among subspecies appear to be "much more important" for maintaining genetic diversity than increasing population numbers, the researchers recommend focusing conservation efforts on creating ways for tigers to travel longer distances, such as wildlife corridors, and potentially crossbreeding wild and captive tiger subspecies.

"This is very much counter to the ideas that many managers and countries have now - that tigers in zoos are almost useless and that interbreeding tigers from multiple countries is akin to genetic pollution," said Hadly. "In this case, survival of the species matters more than does survival of the exclusive traits of individual populations," says the report.

Understanding these factors can help decision-makers better address how development affects populations of tigers and other animals, the study noted.

Iconic symbols of power and beauty, wild tigers may roam only in stories someday soon. Their historical range has been reduced by more than 90 percent. But conservation plans that focus only on increasing numbers and preserving distinct subspecies ignore genetic diversity, according to the study. In fact, under that approach, the tiger could vanish entirely.


http://economictimes.indiatimes.com/envi...333802.cms

 

I don't see any problem in translocating tigers from Ranthambore to Sariska anymore. According with Thapar et al. (2013), the tigers that live now in Rajastan were not native but transported from the Kumaon region when the tigers from the area dissapeared by the over-hunt. So, if we focus on genetic, there is not to much to choose.
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