What’s the News: Due to a vicious disease, the population of the endangered Tasmanian devil
has decreased by at least 70 percent since 1996. The cancer, devil facial tumor disease
, spreads when an infected devil bites another, typically during feeding or mating. Because Tasmanian devils are so genetically similar, their bodies don’t recognize the intruding cancer cells as foreign. But now, researchers have sequenced the genome of two devils
and created a genetic test that could help breeders select genetically diverse mates. The test will help conservationists breed future generations of Tasmanian devils that are prepared for the cancer, as well as other types of diseases. How the Heck:
Stephan Schuster of Pennsylvania State University and an international team of researchers began by sequencing and comparing the genome of two wild Tasmanian devils. Because the devils came from opposite ends of the island, they represented the maximum geographic spread of the species. One of the devils, Cedric, was resistant to two strains of the cancer, while the other, Spirit, was already suffering from five tumors and near death when the researchers captured her.
After analyzing the animal genomes, the researchers sequenced one of Spirit’s tumors. With all the genetic data, the team created a test to determine which wild individuals should be used for captive breeding programs. The model can identify which devils are most resistant to the cancer, and select for the broadest genetic diversity possible. “This is probably one of the only cases where human intervention, doing all the right things, can prevent a species from going extinct,” Schuster told ScienceNews.
As a second phase of the research, the researchers wanted to see how the genetic diversity of Tasmanian devils has changed over time, so they looked at the genome of 175 wild devils and 7 museum specimens. They found that the species’ genetic diversity has been low for past the 100 years, showing that the disease hasn’t reduced the amount of diversity in wild populations.
What’s the Context:
While the devils have been battling devil facial tumor disease for over a decade, it wasn’t until 2009 that scientists developed a blood test to detect the disease. Before the blood test, you could only diagnose infected devils by their facial tumors.
Scientists have long known that the genetic diversity of Tasmanian devils is low. But the new study quantifies past results, showing that devil diversity is only about 25 percent of that in humans. Population crashes caused by human hunting and the introduction of dingoes to the mainland Australia may be to blame, according to New Scientist.
A few years ago, the Australian and Tasmanian governments set up a captive breeding program to ensure the Tasmanian devil doesn't go extinct if all of the wild populations die out.
Image: Wikimedia Commons/Chen Wu