Colourful surprise in cockatoo's tree
Tuesday, 5 April 2011 Anna Salleh
ABC
Some black cockatoos are more closely related to white cockatoos than we
think, according to a new genetic study by Australian researchers.
The findings come from the most detailed ever cockatoo family tree,
published in Molecular Phylogenetics and Evolution.
"You can't really judge a book by its cover until you go in and actually
read the DNA code," says researcher Nicole White, of Murdoch University in
Perth.
Cockatoos may be colourful, charismatic and smart but little has been known
about their evolution.
White says the birds, which are spread around the world, belong to the same
order as parrots and originated in Australia.
"Australia is the hotbed for cockatoo and parrot evolution," says White who
carried out the family tree research as part of her PhD, supervised by Drs
Michael Bunce and Peter Spencer.
White and colleagues compared six genes from 16 of the 21 different species
of cockatoos we see today.
The amount of DNA sequenced allowed the researchers to not only draw up a
family tree, but to use DNA mutations to date when different groups of
cockatoos evolved.
Their research found that cockatoos and parrots branched away from each
other around 40 million years ago.
Not so black and white
But they also come up with some surprising findings.
While many studies have concluded that there were separate white and black
lineages of cockatoos, this study has found otherwise.
It found that the palm cockatoo, a large black cockatoo, was more closely
related to white cockatoos than to other black cockatoos.
They also found the red-headed black-bodied gang gang was more closely
related to the pink-headed and grey-winged galah.
Some previous research suggested the two were closely related based on the
way they flew, but others argued that their colouring was so different they
couldn't be so closely related.
Adapting to climate change
The dated family tree also suggests that a changing climate 10 to 20 million
years ago resulted in the diversity of cockatoos we see today.
"The Australian landscape changed quite radically," says White. "A more arid
climate started to develop."
She says cockatoos responded to the changing vegetation, for example, by
developing beaks there were able to eat the hard fruit of eucalypt trees.
"For the birds to be able to survive, they had to be able to adapt to be
able to eat these new food resources," says White.
As humans replaced native forests with other trees such as fruit and nut
orchards, some cockatoos have also adapted to feed on these, she says.
"They're actually learning how to crawl under fences to get into the nut
orchards," says White.
White says the new DNA sequences can also be used to identify when
endangered birds are being trafficked.
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