Clues found in ancient DNA shed light on devilish condition
This baby Tasmanian devil was checked by a vet at Healesville Sanctuary yesterday. Photo: Joe Armao
TASMANIAN devils suffered from low genetic diversity long before European settlement, according to new research which sheds light on the animal's battle with the deadly facial tumour disease.
Low genetic diversity has been linked to the spread of devil facial tumour disease but it has never been clear when devils, which once roamed the mainland, lost their immune diversity.
Since European settlement in Tasmania, there have been several population crashes, although the cause has been a mystery. However research by scientists from Adelaide and Sydney universities shows that both mainland and Tasmanian devils had shallow gene pools long before the facial tumour disease arrived.
Tasmanian Devil joeys
A Tasmanian devil joey's first vet check. Photo: Joe Armao
This low diversity aided the spread of the disease.
''When a population has low immune gene diversity it means that if one individual is susceptible to a disease then generally the entire population is susceptible,'' said Katrina Morris, from Sydney University's faculty of veterinary science.
Ms Morris is a member of a research team, which for the first time took a genetic approach to the problem. Using ancient DNA retrieved from Tasmanian devil specimens collected over the last 200 years and stored in museums, scientists established that low genetic diversity in Tasmanian devils dates back thousands of years.
The research included testing the oldest marsupial genes to have ever had their genetic code sequenced - using samples taken from mainland devil specimens at least 3000 years old.
Tasmanian devils disappeared from the Australian mainland about 3000 years ago, possibly a result of competition from dingoes.
''What we found was not what we initially expected,'' said Ms Morris, the lead author of a paper outlining the findings published in Biology Letters on Wednesday.
''We found that there was actually very low immune diversity in Tasmania across the 200 years and this was the case with the samples from before European arrival, so it looks like low immune diversity pre-dates European arrival in Tasmania.''
Ms Morris said the findings reinforced the importance of breeding programs and the importance of ensuring the captive animals remained as genetically diverse as possible.
Devil facial tumour disease is an aggressive parasitic cancer first described in 1996. Spread by devils biting each other's heads when fighting over food, the disease has caused a collapse in the devil population from about 130,000-150,000 in the mid-1990s to under 24,000 mature individuals now.
In 2009, the Tasmanian devil was listed nationally as endangered. Unless spread of the disease can be stopped, extinction in the wild is likely within 35 years.