The deadly devil facial tumour disease (DFTD) has been responsible for the decline of two-thirds of the species population over the last three decades. But now, new research has found that DFTD is evolving to coexist with Tassie devils and is unlikely to lead to their extinction.
The new study, in the journal Evolutionary Applications, has found that changes in tumour genetic diversity in long-term affected areas has resulted in lower infection rates and a reduction in devil population decline.
Dr Rodrigo Hamede, a disease ecologist at the University of Tasmania and lead author of the paper, says that this could be happening due to changes in how deadly or transmissible the tumour variants are, or due to devils developing resilience against DFTD, or a combination of both.
“We know that shortly after DFTD arrived in West Pencil Pine [in the northwest of Tasmania] in 2006, it reached its peak of genetic diversity,” he says.
“Over time, some DFTD variants were weeded out, while a few became better adapted and fixed in the population.
“This suggests that, through selective processes, the tumour is fine tuning its optimal virulence (how deadly it is), a trade-off between transmission rate and disease-induced mortality in the animals.
“This means that DFTD is very unlikely to drive the devil to extinction, but it also means the disease will not disappear, it’s an evolutionary deal to coexist with each other.”
But while a reduction in infection rates and population decline is good news, Hamede argues that it’s still critical to continue to monitor and protect long-term affected devil populations.
“These adapted populations are particularly valuable when planning conservation efforts, as they possess key adaptive traits for future generations of devils,” he says.
“We also need to make sure we reduce all other threatening processes, such has habitat loss and fragmentation, genetic deterioration in local populations and roadkill.
“Extinctions are rarely driven by one factor, but act in synergy with other threatening processes.”