THE Nullarbor Plain is daunting not only for people to cross. Genetic research on Australian cockatoos suggests this wide, dry expanse was behind the evolution of white-tailed black cockatoos in the south-west corner of the continent.
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Nicole White, a wildlife geneticist, said her DNA study revealed these endangered native birds were closely related to the yellow-tailed black cockatoos that are prevalent on the east coast, and the two species last shared a common ancestor about 1.3 million years ago.
This was about the time the plain became drier, which could have isolated a group in the south-west.
''We believe the aridity of the Nullarbor was the driver of speciation for the white-tailed black cockatoos,'' she said.
The study of 16 types of cockatoos has also thrown up some surprises and could help identify smuggled bird eggs and prevent illegal trading of rare cockatoo species, which can fetch up to $30,000 on the black market.
It showed appearances could be deceptive, with a black cockatoo - the palm cockatoo - being closer to white cockatoos than other black ones.
''Just because some cockatoos might look similar, this doesn't necessarily mean they are closely related,'' said Ms White, a PhD student at Murdoch University.
Gang-gang cockatoos, with their red heads and black bodies, are also much closer to galahs - with their pink heads and grey wings - than had been thought.
Cockatoos have a crest on their heads that they can move up and down. Parrots lack this but, unlike cockatoos, can have green and blue feathers.
The two groups, which are both very clever, split from each other about 40 million years ago, according to the study, which is published in the journal Molecular Phylogenetics and Evolution.
The cockatoos began to diverge into today's 21 different species about 10 million to 20 million years ago, with the expansion of dry habitats containing grasslands and eucalypts, which they favoured.
Ms White said the research could help in cases of egg smuggling by identifying the embryos through their DNA. ''It's very hard to tell the species of a bird just by looking at its egg,'' she said.
Understanding the genetics of the white-tailed black cockatoos was important for working out whether they had the genetic diversity to adapt to environmental changes.
It was also possible to carry out ''paternity testing'' of the white-tailed black cockatoos to ensure that sellers who claimed to have bred them under licence had not collected them from the wild.
