Australia — SCIENTISTS have used fossilised pollen and DNA extracted from gumleaves to establish that bushfires appeared in Australia more than 50 million years earlier than thought.
The findings, which take bushfires back to the time of the dinosaurs’ demise, mean fire probably contributed to transforming the prehistoric landscape from lush rainforest into dry eucalypt forest.
Australian National University’s Mike Crisp and his colleagues developed an evolutionary family tree for the myrtle family – of which the eucalyptus is a member – by extracting DNA from leaves. Advertisement: Story continues below
The DNA helped document the species’ evolution back 80 million years, but researchers could not pin down when the eucalypt developed the fire-resistant feature known as epicormic buds, which aid regeneration.
”The DNA alone won’t put a timescale on it; you need fossils of known age. That’s where the pollen comes in,” Professor Crisp said. ”The trick is to work out where these fossils go on the evolutionary tree and when you’ve done that you can put the timeline on the tree and work out when things happened.”
Using more than 100 pollen fossil samples, the research team was able to establish that eucalypts developed the buds about 62 million years ago. This puts bushfire activity in Australia back to more than 60 million years ago – rather than the previous view that fire dated back just 10 million years.
Professor Crisp said the findings coincided with the time the landscape of Australia started to change, when the ancient ancestors of the eucalypt moved out of the rainforest and into the woodlands.
”It means you have two lines of evidence pointing to fire originating at that time,” Professor Crisp said.
”One is to do with the anatomy of the eucalypts and their ability to re-sprout, and the other to do with the kinds of habitat they grew in. And the timing was the same for both.”
The lead author of the paper, Professor Crisp, worked with colleagues from Charles Sturt University, the University of Tasmania and the University of Queensland.
The results of the study are published today in the journal Nature Communications.