In the face of diseases and pathogens, many animal populations undergo shifts in their genetics, sometimes succumbing to them and ultimately vanishing from the face of the Earth. Other times, animals can successfully evolve and adapt in response to disease and adversity, and a new study on Tasmanian devils suggests that the massive carnivorous marsupials – the largest in the world – are doing just that.
A team of Washington State University researchers claims that Tasmanian devils are undergoing genetic evolution in response to devil facial tumor disease (DFTD), a rapidly spreading form of contagious cancer first detected in 1996 that almost always leads to death.
Contrary to what current biological models predict, the findings suggest that the Tasmanian devils may avoid extinction and could help scientists in their quest to better understand how animals evolve in response to pathogens over short periods of time.
DFTD is considered to be the most deadly form of only three types of contagious cancers in the world. Since Tasmanian devils are known to frequently display aggressive behaviors towards each other, such as biting of the face, they are particularly susceptible to DFTD. Although the disease was only discovered twenty years ago, it has already led to the death of approximately 80 percent of the species in Tasmania, the only place on the Earth where they currently exist.
In order to determine the possibility that the species has evolved some sort of genetic resistance to DFTD, Storfer and his team sought out to determine parts of the marsupial's genome in the remaining population that were unique from the population at large.
"If a disease comes in and knocks out 90 percent of the individuals, you might predict the 10 percent who survive are somehow genetically different," says Paul Hohenlohe of the University of Idaho and co-author of the study. "What we were looking for were the parts of the genome that show that difference."
Using genomic data that was gathered from three sites by researchers at the University of Tasmania prior to and after the DFTD outbreak in 1996, the team was able to get a close look at the Tasmanian devil's DNA response to the disease.
The team discovered that in the DNA samples from all three sites, there are two unique genomic regions that responded the most to the selection pressures created by DFTD. Furthermore, five of seven of the genes in these two areas are connected to cancer and immune function in other mammals.
As of now, the team is still trying to determine exactly what function these genes have in terms of cancer and immune function, but the changes exhibited by the DNA samples in response to selection pressures suggests that the Tasmanian devils are indeed evolving a resistance to DFTD.
The team eventually hopes to breed Tasmanian devils with DFTD-resistant DNA and use these breeds to diversify populations with cancer-resistant genetics, an alternative to developing vaccines that fight the disease.
The findings were published in the journal Nature Communications.
Source: Washington State University via EurekAlert
