Secrets from beyond extinction: the Tasmanian Tiger
The entire thylacine genome has now been sequenced, revealing the apex marsupial predator was in poor genetic health and may have struggled to fight disease had it survived.
Floating in a small jar of alcohol sits one of Australia’s rarest specimens.
The jar, labelled collection number C5757, holds a juvenile Tasmanian tiger or thylacine, one of the best-preserved extinct species, now held in Museums Victoria’s Collection.
The now-extinct Tasmanian tiger’s genome has now been sequenced, revealing the species had low genetic diversity. Picture: TMAG Tasmanian Museum and Art Gallery
As the animal became rarer, museums everywhere clambered to have a thylacine on show, and they are now its last refuge after being hunted to extinction in 1936.
Using techniques never imagined when the last thylacine died in Hobart Zoo last centry, a team led by the University of Melbourne have now sequenced the genome of the Tasmanian tiger (Thylacinus cynocephalus), making it one of the most complete genetic blueprints for an extinct animal.
For project leader Professor Andrew Pask, the thylacine is his labour of love. Over ten years ago, he and an international team first resurrected a Tasmanian tiger gene from preserved pelt, but the DNA was too fragmented to obtain the whole genome.
So, they searched museums’ world-wide databases and found specimen C5757 in Museums Victoria’s collection – a young thylacine pup. Because the Tasmanian tiger was a marsupial, which are mammals with a pouch, this pup specimen could be preserved in its entirety, allowing the research team to extract DNA and use cutting-edge techniques to sequence the thylacine genome.
Associate Professor Andrew Pask says the results provide the first full genetic blueprint of the largest Australian apex predator to survive into the modern era.
“The genome allows us to confirm the thylacine’s place in the evolutionary tree. The Tasmanian tiger belongs in a sister lineage to the Dasyuridae, the family which includes the Tasmanian Devil and the dunnart,” says Associate Professor Pask, from the School of Biosciences.
Importantly, the genome has also revealed the poor genetic health, or low genetic diversity, the thylacine experienced before it was over-hunted. The Tasmanian Devil is now also facing a ‘genetic bottleneck’ which is a likely result of their genetic isolation from mainland Australia for the last 10,000 to 13,000 years.
However, the genome analysis suggests that both animals were experiencing low genetic diversity before they became isolated on Tasmania. This, in turn, suggests that Tasmanian tigers may have faced similar environmental problems to the Devils, had they survived, such as a difficulty overcoming disease.
“Our hope is that there is a lot the thylacine can tell us about the genetic basis of extinction to help other species,” Associate Professor Pask says.
“As this genome is one of the most complete for an extinct species, it is technically the first step to ‘bringing the thylacine back’, but we are still a long way off that possibility.
“We would still need to develop a marsupial animal model to host the thylacine genome, like work conducted to include mammoth genes in the modern elephant. But knowing the Tasmanian tiger was facing limited genetic diversity before extinction means it would still have struggled similarly to the Tasmanian Devil if it had survived.”