Ancient DNA reveals moa's true colours

Anna Salleh, ABC
Wednesday, 1 July 2009

The plumage of extinct New Zealand moa birds is being reconstructed with the help of DNA from ancient feathers. Ancient DNA expert, Nicolas Rawlence of the University of Adelaide and colleagues report their findings in this week's Proceedings of the Royal Society B.

"For the vast majority of moa we have no idea what the actual plumage was," says Rawlence, who is researching the moa for his PhD. The vegetarian Moa, which stood up to 2.5 metres tall and weighed around 250 kilograms, dominated the New Zealand environment, before going extinct after humans arrived around 1280 AD.

Rawlence says when artists reconstruct the big bird, they refer to related species, like the emu, as a model for its plumage. But do moas really look like emus?

To help answer this question Rawlence and colleagues extracted DNA from the oldest feathers yet discovered. These surprisingly intact moa feathers were excavated from rock shelters around New Zealand, dating back 2000 to 3000 years ago.

DNA analysis enabled the researchers to work out the feathers belonged to four of the 10 different species of moa that once existed. By digitally comparing the colour of ancient red-crowned parakeet feathers found alongside the moa feathers, with living parakeet feathers, the researchers could determine that the feathers at the site had not faded.

Artistic licence

Rawlence and colleagues then compared the feathers to those from big birds alive today that have similarly patterned feathers. They used a computer program and "a bit of artistic licence", to recreate what they think the plumage of the extinct moas looked like.

The researchers found a white-tipped feather, mapped to the heavy footed moa (Pachyornis elephantopus), was similar to the feathers of a particular species of kiwi. When the feathers were overlayed they produced the same speckled plumage as seen in the kiwi. Rawlence says other moa species had much drabber plumage, possibly for camouflage.

He says it's possible that the plumage the team has reconstructed may differ on different parts of the body, or between sexes of the same species. "It's not definitive," says Rawlence. "It's designed to act as a standpoint for other research and discussion."

Method to benefit museums

Prior to this study most researchers believed it was only possible to extract ancient DNA from a feather's quill tip, which inserts into the skin of the animal, says Rawlence. But he and colleagues have shown it's possible to extract DNA from the shaft and barbs of the feather.

This means that when scientists are sampling rare museum specimens they don't have to pluck the whole feather from the skin, but can simply clip off a little from the top of the feather.

"It means you can now sample these specimens with minimal damage, which will make museums very happy," says Rawlence. Rawlence is now using ancient DNA to work out how climate change affected the moa before humans arrived in New Zealand.

As in Australia, there is a debate over the role of climate change and humans in the demise of megafauna of this kind. The question is whether climate change had already put downward pressure on the moa populations before humans arrived, says Rawlence.

http://www.abc.net.au/science/articles/2009/07/01/2612655.htm