1 July 2000

The Sydney Morning Herald

[Australia]

Pines' clone DNA baffles scientists

by James Wooford

Environment Writer

After six years of research, scientists have been unable to find any difference between the DNA of one Wollemi pine and another, baffling the nation's leading plant geneticists.

Genetic variability is the fuel of evolution, and yet these trees are impossibly perfect clones.

In 1994, a bushwalker, David Noble, returned to civilisation with a fragment of a 40-metre "dinosaur tree" -- it had a fossil record stretching back 120 million years.

Mutations in DNA allow one individual to gain an advantage over another, a process thought to be fundamental to the health of a species. Variability is also the basis of Darwin's theory of natural selection.

Low genetic variability has always been regarded by scientists as a fast track to extinction.

This is a basic rule of genetic theory and one which the Wollemi pine, a new member of an ancient family called the Araucariaceae, does not seem to be obeying. The trees (only 40 adults are known), in spite of their apparent genetic problems, are remarkably strong, healthy and reproducing viable seeds and seedlings.

The trees also appear to be cloning themselves by sending out roots which break through the surface and eventually become adults in their own right.

Clones have identical DNA, as do identical twins. But if a pair of clones or a pair of twins reproduce, then their offspring will be genetically different. Wollemi pine seedlings, however, have identical DNA to the parent trees.

After searching 1,000 points on the trees' genome, using the most sensitive DNA analysis equipment available, a plant geneticist at the Australian National University, Dr. Rod Peakall, has been unable to find a single trace of any genetic variability.

He has searched the DNA of Wollemi pines from the two known stands, both in a single canyon system in the Wollemi Wilderness, and from seedlings.

So far the genetic fingerprint of every Wollemi pine has turned out to be bafflingly identical.

What has most stunned Dr. Peakall is that the two stands of the Wollemi pine are two kilometres apart and separated by such rugged terrain that he ways, in a report prepared for the NSW National Parks and Wildlife Service, any genetic interchange is extremely unlikely.

The two sites are likely to have been independent of each other for at least 10,000 years -- since the end of the last ice age. Yet both stands of pines, remarkably, share an indistinguishable genetic code.

In a new scientific paper just published in the Australian Journal of Botany, Dr. Peakall and his colleagues write that the "Complete lack of genetic variation" has meant they are so far unable to explain what forces are at work deep in the three' canyon.

"Few, if any, other plant species are known to exhibit such apparently low levels of genetic diversity," the paper says.

Dr Peakall hopes to mount an even more comprehensive search for variability in the genome of Wollemipines.

"Wollemia may be an exception that disproves a rule", he said. "The assumption has always been that genetic diversity is good because it is the basis of natural selection. The Wollemi pine might actually prove that in some systems it is possible to have exceptionally low variability and yet survive for thousands of years."

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