They travelled from China to Turkey and then to Siberia, where they might have resettled
TEN thousand years ago, the tiger reigned over Eurasia from the Sunda Islands of Indonesia to India to eastern Turkey and up north into Siberia. Environmental changes and human influence drove some of its subspecies--the Caspian, Balinese, Javan--to extinction. The Caspian tigers once prowled the Central Asian forests. The last survivor was shot down in Turkey in the 1970s. Or so it was believed. New
dna evidence reveals that it might not be extinct at all. It might have travelled to Siberia and what we now know as the Siberian tiger might after all be the Caspian tiger.
When the Egyptians were still perfecting the art of agriculture, tigers were using the silk route to migrate from eastern China to the region around the Caspian sea. The last ice age was retreating, making the route usable for animals.After colonizing present day Turkey, the tigers travelled to Siberia.
Researchers from the UK, US and Israel analyzed mitochondrial
dna from 20 samples of the Caspian tiger taken from museums around the world. Mitochondrial
dna is useful for tracking ancestry as it is inherited from the mother and is passed on unchanged from generation to generation. The group found that the Caspian and Siberian tigers differed by just one group of genes located near each other on a chromosome. This indicated that the two were too closely related to be different subspecies.
The study compared the
dna of Caspian tigers with that of other sub-species analyzed by an earlier study. A family tree was created. The tree showed the Indochinese subspecies has common genes with Caspian tigers. It also showed that the Siberian tiger is the youngest subspecies and is closely related to the Caspian tiger.
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| Caspian tigers went to Turkey via the silk route |
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The researchers suggested three possible routes the tigers could have taken for dispersal through India, north through Siberia
or via the silk route. They also suggested that of the two subspecies living in China--the South China and Indochinese tigers--it was the latter that migrated. They explained that the South China tiger, whose territory lay between that of the Indochinese and Siberian tigers', is not closely related to the Siberian tiger. If the South China tiger had migrated north then itwould have been related to the Siberian tiger. Similarly if the Indochinese tiger had migrated north, it would have had a lot in common with the Siberian subspecies. The silk route thus turned out to be the most logical possibility. The Indochinese subspecies migrated through the silk route and reached West Asia. Later it migrated from Turkey to Siberia. This explained the close relationship between Caspian and Siberian tigers, concluded the researchers.
The study, published in the January issue of
PLoS One is important if there is ever a plan to reintroduce the Caspian tiger into Turkey's forests, said Ji Mazk who has researched tiger biogeography and is curator at Shangai museum.
"This study establishes a close link between the extinct Caspian and still living Siberian tiger. But the silk route hypothesis is just an assumption. It is not easy to come to a definite conclusion since climates and habitats have varied considerably over the last 20,000 years," said Andrew Kitchener of the National Museums of Scotland, who has studied evolution and biogeography of tigers.
