DNA sequencing shows insects crossed oceans then migrated from treetops to the ground to adapt to ancient climate change
A new paper shows that the ancient ancestors of termites found in northern Australia crossed vast distances over oceans, and then followed an evolutionary path similar to humans, migrating from tree-tops to the ground.
Mounds sometimes reaching as high as eight metres and housing millions of individual insects are seen in the Northern Territory, Western Australia and far north Queensland, built by cathedral termites. Relative to the animals’ 3mm height and the average human height the termite mounds are the equivalent to four of the world’s tallest structure, the Burj Khalifa skyscraper in Dubai, stacked on top of each other.
Little was known about the termites’ origins until this research, said Associate Professor Nathan Lo, the co-lead author of the paper from the University of Sydney.
DNA sequencing showed that today’s cathedral termites descend from the first “nasute termites” to arrive in Australia up to 20m years ago from Asia or South America.
“It’s a strange result but we’re very confident about it,” said Lo. “The closest relatives of these mound-building termites in Australia are actually tree-nesting termites that live in Asia and South America.”
He believed that termites arrived in Australia after crossing long distances of ocean on plant matter following tsunamis or large storm events. The researchers found this colonisation had happened three times in the past 20m years.
These first settlers also lived in trees in coastal areas but over time began to build mounds on the ground and feed on litter and grass as they adapted to the arid conditions of northern Australia.
Lo said the termites’ relocation was driven by change in climate and environment after Australia shifted from a forest-covered continent 20m years ago to a much drier landscape.
As the forests succumbed to Australia’s dry conditions about seven to 10m years ago, the tree-dwelling termites sought more moisture in the earth, he said. “That’s why they started to build mounds.”
Humans would later follow a similar evolutionary path, said Lo, with our ancestors living in trees as recently as the last 4m years.
“These amazing mounds we see in the north of Australia, we didn’t know if they were 100m years old, 50m years old. Now we know it’s more likely that within the last 10m years that they’ve popped up.
“They weren’t here when Australia separated from Gondwana some 100m years ago – they evolved here relatively recently due to ancient climate change.”
The study, published on Wednesday in the Royal Society journal Biology Letters, was led by the University of Sydney in collaboration with Purdue University in the United States, the CSIRO National Research Collections Australia, the University of Western Australia and the University of New South Wales.
Online Source: The Guardian