Researchers have found that Tasmanian devils are rapidly evolving in response to a contagious form of cancer, devil facial tumor disease. The disease is fatal but a small percentage of the population has genes that may protect them. The findings are in a paper just published in the journal Nature Communications.
Tasmanian devils are the largest carnivorous marsupials. The species is endangered and they are only found in Tasmania. Tasmanian devils are highly aggressive, a trait that contributes to the spread of a contagious cancer called devil facial tumor disease (DFTD). DFTD is transmitted as the animals bite each other on the face, a common behavior for devils. The disease is fatal and has wiped out at least 80% of all Tasmanian devils since its discovery in 1996. DFTD is one of only three known forms of contagious cancer.
A team of researchers analyzed Tasmanian devil DNA samples across three collection sites. They compared samples taken before and after the outbreak of DFTD. Tasmanian devils exhibit very little genetic variability and this might have made the populations especially vulnerable to disease. The team found that there were some minor differences between the pre-DFTD and post-DFTD groups. Two small regions of the genome had changed and this was true for any of the recent samples, regardless of the collection site. Most of the genes found in these regions are associated with immune system functions and cancer resistance in mammals. This suggests that Tasmanian devils are evolving in response to DFTD; the only devils surviving are ones with these resistance genes.
Tasmanian devils are quickly evolving to cope with DFTD. The disease is capable of wiping out most of the population but some individuals are surviving due to a unique set of genes. These findings show that Tasmanian devils may not be doomed. The authors believe that DFTD-resistant Tasmanian devils could be bred and reintroduced into the wild. The study also provides new insights into disease transmission and evolution.
Brendan Epstein et al. Rapid evolutionary response to a transmissible cancer in Tasmanian devils. Nature Communications (2016).