Living tigers are severely endangered in their fragmented range across Asia numbering as low as 3000 wild individuals that remain in a handful of tiger range countries. Tigers have been traditionally subdivided into eight principal subspecies based upon geographic provenance and subtle morphometric traits for over a century. Four of these subspecies (Javan, Bali, Caspian and South China tigers) disappeared from their former natural range in the 20th century, leaving relict populations of the Bengal (Indian), Indochinese, Sumatran and Amur (Russian Far East and northeast China) surviving today in small vulnerable populations, objects of intense conservation concern and protection.
Tiger subspecies recognition and classification is important because the subspecies boundaries often coincide with geo-Ââ€political boundaries between countries that do not always agree on a unified conservation approach. Further, subspecies recognition has been somewhat controversial since selected morphological traits and geographic boundaries of tiger range are dynamic, capricious and imprecise. Today, an international team of scientists from China, USA, UK, Israel, Russia, and Qatar released a comprehensive molecular genetic reassessment of tiger subspecies population structure, their relative relationship and a plausible interpretation of tiger natural history that led to the present disposition of surviving subspecies.
Published online today in the May 1, 2015 edition of the Journal of Heredity, the report describes DNA signatures for 145 individual tiger specimens including so-Ââ€called â€œvoucher specimensâ€ of tigers from verified geographic origins including Eurasian museum specimens for the extinct Caspian, Javan and Bali tiger subspecies.
The culmination of a ten-year study using both mitochondrial DNA sequence and nuclear microsatellite markers led by Shu-Jin Luo of Peking University and Stephen OBrien of Theodosius Dobzhansky Center for Genome Bioinformatics in St Petersburg, Russia, revealed clear molecular genetic distinctiveness among Amur, Bengal, Indochinese and Sumatran tigers. The teamâ€™s first results appeared in 2004 announcing the Malayan tiger splitting from its Indochinese counterpart as a distinct, new fifth living tiger subspecies. However todayâ€™s report offers evidence that the extinct Javan and Bali tigers were near indistinguishable in molecular genetic distance from Sumatran tigers, as the extinct Caspian tigers are similarly near identical to the surviving Amur tiger subspecies, raising the prospect of revising subspecies nomenclature.
The new results, though probably not the last fine-Ââ€tuning of our understanding of tiger subspecies status, are important in designing management strategies for protecting each surviving subspecies of tiger and stabilizing the march toward extinction that tigers are clearly suffering. The identified diagnostic markers also provide powerful methodology for forensic identification of subspecies intercrosses in captive populations or subspecies identification of trafficked bones and skins in illegal trade enforcement. As human DNA forensics revolutionized capital crime prosecution, the tiger DNA profiles offer powerful tools in wildlife protection as well as in reducing illegal wildlife commerce.
Shu-Ââ€Jin Luo, Ph.D. Principal Investigator College of Life Sciences Peking University Beijing 100871, China Tel: +86-Ââ€13811457516
Stephen J. O'Brien, Ph.D. Chief Scientific Officer
Theodosius Dobzhansky Center for Genome Bioinformatics St. Petersburg State University
41 Sredniy Prospekt
St. Petersburg, Russia 199004 Russia (011)+7 981 801 7983
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