The research team was led by Joel Cracraft a curator in the American Museum of Natural History's Department of Ornithology. The team analyzed blood samples of thirty-four captive tigers, representing all tiger groups with the exception of the South China tiger, and one lion, to serve as a point of comparison. The mitochondrial DNA sequenced from the blood revealed that Sumatran tigers share three unique genetic markers found in none of the other tigers. These features support the interpretation that Sumatrans are a distinct species, and all other tiger populations on the mainland can be grouped together as a single species.
The new research supports the hypothesis that Sumatran tigers were geographically isolated and became differentiated from their counterparts on the mainland when Sumatra was cut off from the continent by a rise in sea level between 6,000 and 12,000 years ago. The genetic divergence of Sumatrans from other tigers mirrors the divergence already recognized as having occurred in the Sumatran rhinoceros, which is distinct from mainland rhinoceros populations. While the four groups of mainland tigers are currently geographically isolated from one another, this is the result of recent habitat destruction by humans. Previous to this, the mainland tigers's range was uninterrupted, allowing them to interbreed and preventing them from developing into separate species.
The ability to recognize the Sumatran tiger as genetically distinct is critical
to breeding programs, which are designed to maximize the genetic diversity of
the animals they seek to protect. Regulation of the illegal trade in tigers is
also bolstered by the discovery, because the use of newly discovered genetic
markers ensures reliable identification of products produced from Sumatran
tigers. Finally, since conservation plans for wild populations depend on
Contact: Elizabeth Chapman
American Museum of Natural History