Tasmanian devils evolve defence against deadly cancer
It appears the remaining population of native marsupials evolved some genetic fortification against the aggressive disease in only four to six generations. Amy Middleton reports.
Tasmanian devils may be adapting to fight back against the deadly contagious cancer that wiped out 80% of the species, according to a new study.
Devil facial tumour disease was first reported in Tasmania in 1996. In the 20 years since it has decimated some populations by a staggering 95%.
But many devil communities are surviving against the odds, and an international research team led by Andrew Storfer at Washington State University decided to investigate why.
“If a disease comes in and knocks out 90% of the individuals, you might predict the 10% who survive are somehow genetically different,” explains Paul Hohenlohe, a biologist at 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.”
To uncover the evolution of devil facial tumour disease and its hosts, the team examined genetic data collected by researchers at the University of Tasmania in Australia before and after the outbreak.
They studied the genomes of 294 individual devils from three sites across Tasmania. They found two regions that dramatically changed during the devil facial tumour disease outbreak, suggesting they contained genes that were passed down when the animals bred during the decline.
According to the paper, published in Nature Communications, five of the seven genes across these two regions have been shown to relate to immune function and cancer risk in other mammals, suggesting Tasmanian devils could be evolving resistance to devil facial tumour disease.
“Our study suggests hope for the survival of the Tasmanian devil in the face of this devastating disease,” Storfer says.
“Ultimately, it may also help direct future research addressing important questions about the evolution of cancer transmissibility and what causes remission and reoccurrence in cancer and other diseases.”
Devil facial tumour disease is one of just three known contagious cancers. It is spread from devil to devil through biting, which is a crucial part of the marsupial’s social interaction.
Behavioural biting coupled with low genetic diversity in devil populations created what the paper calls a “perfect storm” of conditions for the disease to wreak havoc on the species. But the evolutionary response of the diseased devils is, according to the researchers, unprecedented.
“Overall, our results reflect a rapid evolutionary response to this strong selection imposed by [devil facial tumour disease], and such a response to a highly lethal, novel pathogen has rarely if ever been documented in wild populations.”
The researchers say more study is needed to identify the exact functions of the genetic regions in question.
Once disease-resistant genes is observed, the researchers hope robust devils can be bred to diversify the gene pool to help pull the species back from the brink.