An international team of scientists has confirmed the Tasmanian Tiger or thylacine (Thylacinus cynocephalus) had limited genetic diversity prior to its extinction.
The Tasmanian Tiger, Thylacinus cynocephalus (Benjamin A. Sheppard)
The study, published in the journal PloS-ONE, provides insights into the genetic health of the thylacine before it was exterminated by hunting.
“The latest study revealed that the Tasmanian Tiger had the same or even less genetic diversity than its close relative the Devil,” said lead author Dr. Brandon Menzies, a Honorary Fellow of the University of Melbourne. “Hence, Tasmanian Tigers may have faced similar environmental problems to the Devils, had they survived.”
“Due to the similarly poor genetic diversity of the animals, this new data suggests that the genetic health of the Tasmanian Tiger and Devil may have been affected by the geographic isolation of Tasmania from mainland Australia approximately 10-13 thousand years ago,” the scientist said.
The Tasmanian Tiger has been the focus for biologists due to its unique evolution in Australia and extinction. Having evolved from a marsupial into a mammal that is very similar to a dog or wolf, but being marsupials, the females had a pouch in which they carried their young.
“While the thylacine was hunted to extinction due to the imposition of a government bounty from 1888-1909, with the last known animal dying in captivity in 1936, one question that continued to puzzle biologists was how genetically diverse the thylacine population was prior to its extinction,” Dr. Menzies explained.
Using a combination of traditional DNA sequencing methods and next generation sequencing technology, the scientists demonstrated the very limited DNA variability between individual thylacine specimens.
They compared mitochondrial DNA extracted from 14 museum specimens that were between 102-159 years old and revealed that the thylacine specimens were more than 99.5 per cent similar over a portion of DNA that is normally highly variable between individual animals.
“If we compare this same section of DNA, the Tasmanian Tiger only averages one DNA difference between individuals, whereas the dog, for example has about 5-6 differences between individuals,” Dr. Menzies said.
“In a direct comparison with other species, the thylacine averages about 5-10 DNA base differences over the coding sections of the mitochondrial genome. This is quite low when compared to other species including the wolf (77) or African humans (85). The Tasmanian Devil has about 10 DNA differences between individuals over the whole genome, which is also low. This work highlights our need to understand all of Tasmania’s and Australia’s unique flora and fauna so they are also not lost to extinction.”
“This new study confirms the relatively low genetic diversity in the Tasmanian Tiger which sadly was hunted to extinction,” concluded Prof. Marilyn Renfree of the University of Melbourne, a study co-author. “We cannot bring the Tiger back to life, but at least we can continue to learn as much as possible about these iconic marsupial carnivores.”
