May 23, 2014
New Zealand’s Kiwi Did Not Originate In Australia
Brett Smith for redOrbit.com - Your Universe Online
New Zealand’s iconic kiwi is not related to Australia’s emu, but instead is derived from the extinct Madagascan elephant bird, according to a new study in the journal Science. The study also concluded that both of these flightless birds were once able to take to the air.
With the kiwi being about the size of a chicken and the Madagascan elephant bird standing around 6 to 9 feet tall – the two make for a bit of an evolutionary odd-couple. The study’s counter-intuitive discovery was based on DNA taken from the bones of two elephant bird species.
"This result was about as unexpected as you could get," said study author Kieren Mitchell, a PhD candidate at the University of Adelaide in Australia, in a recent statement. "New Zealand and Madagascar were only ever distantly physically joined via Antarctica and Australia, so this result shows the ratites must have dispersed around the world by flight."
The study’s results contradict research conducted in the 1990s which found the closest living relatives of the kiwi were the Australian emu and another flightless bird called the cassowary.
"This has been an evolutionary mystery for 150 years. Most things have been suggested but never this," Alan Cooper, a University of Adelaide professor who worked on the 1990s study, told the Associated Press (AP). "The birds are about as different as you can get in terms of geography, morphology and ecology."
"It's great to finally set the record straight, as New Zealanders were shocked and dismayed to find that the national bird appeared to be an Australian immigrant," Cooper said in the University of Adelaide statement. "I can only apologize it has taken so long!"
The latest study also used a genetic analysis to determine when the elephant bird and the kiwi, both considered part of the flightless "ratite" bird family, took separate evolutionary paths.
"The evidence suggests flying ratite ancestors dispersed around the world right after the dinosaurs went extinct, before the mammals dramatically increased in size and became the dominant group," Cooper said. "We think the ratites exploited that narrow window of opportunity to become large herbivores, but once mammals also got large, about 50 million years ago, no other bird could try that idea again unless they were on a mammal free island – like the Dodo."
"We can now see why the evolutionary history of the ratites has been such a difficult problem," said study author Mike Lee, of the South Australian Museum and University of Adelaide. "Many of them independently converged on very similar body plans, complicating analysis of their history."
"We recently found fossils of small kiwi ancestors, which we suggested might have had the power of flight not too long ago," said study author Trevor Worthy, a biologist at Flinders University in Australia. "The genetic results back up this interpretation, and confirm that kiwis were flying when they arrived in New Zealand.”
"It also explains why the kiwi remained small. By the time it arrived in New Zealand, the large herbivore role was already taken by the moa, forcing the kiwi to stay small, and become insectivorous and nocturnal,” he added.
The study was based on specimens from Te Papa, New Zealand's national museum.
"The New Zealand kiwi is an integral part of this country's culture and heritage. It's fitting that Te Papa's scientific collections have been used to resolve the mystery of its origins,” said Alan Tennyson, the museum’s curator.