This was published 7 years ago
Frogs breed with their siblings and cousins after bushfires
By Bridie Smith and Science Editor
Three months after the Black Saturday bushfires incinerated the bushland around Kinglake, Jane Melville returned to check on her precious frogs.
For the previous two years she had been studying the wild populations of two of the area's more common species: the southern brown tree frog and plains brown tree frog. Returning to the area north east of Melbourne that had been scorched by the firestorm was an anxious moment.
Museum Victoria herpetologist Jane Melville found frogs around Kinglake had a shallower gene pool after Black Saturday, due to inbreeding.Credit: David Paul
"I didn't quite know what to expect," the Museum Victoria herpetologist admitted. "We could have gone out there and found absolutely no frogs."
Instead the frog calls that greeted Dr Melville and her colleagues lifted their spirits: there was a chorus in the recovering bush.
The genetic diversity of the southern brown tree frog fell after the Black Saturday fires.Credit: David Paul
However the team's hopes that frogs were resilient to fire have been shattered by the results of their most recent study, published on Tuesday.
While the calls that greeted the researchers each winter breeding season after the 2009 bushfires were robust in number, genetic testing has revealed they are alarmingly limited in diversity.
Or to put it another way, the surviving frogs have such limited choices of mates that they are breeding with their siblings and cousins.
"I was surprised at how dramatic inbreeding was. There was a huge spike after Black Saturday," Dr Melville said. "If it keeps going like that, then the populations would be at risk of extinction. It's that dramatic."
The plains brown tree frog was a part of the study.Credit: Robert Zugaro
Inbreeding shrinks a population's gene pool, compromising its ability to fend off threats such as new and emerging diseases or an ability to adapt to a changing climate.
Up to 40 per cent of amphibian species are facing extinction, with the highly-contagious chytrid fungus one of the most serious threats.
Jane Melville's research found all is not what it seems for frogs after bushfires.Credit: David Paul
Modelling conducted as part of the study suggested an 80 per cent chance that a Victorian tree frog population would become extinct if 10 intense fires occurred this century.
Traditionally frog surveys count calls. The size of a population is estimated based on the number of calls recorded during the breeding season. However the results of Dr Melville's study suggests this is not an accurate reflection of the health of a population.
"It seemed in a lot of cases that frogs are resilient to fires but this may not be the case," she said.
Dr Melville said if increased inbreeding as a result of bushfire had been recorded in an abundant species, then it was probably also the case for threatened species, such as the growling grass frog, which calls the area home. It was also likely to be seen amongst reptiles and small mammals which are not as mobile as larger animals that can escape fire and seek breeding mates further afield.
The work, by researchers from institutions including Monash and Melbourne universities, is published in The Journal of Applied Ecology on Tuesday.