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New discovery gives hope of survival for critically endangered Wollemi pine

Marcus Strom

An Australian conifer that traces its lineage to the Jurassic period 150 million years ago was long thought extinct. Only traces of its ancestor Agathis jurassica existed in the fossil record.

Then one day in 1994 David Noble, a park ranger on a bushwalking holiday, abseiled into a secluded Blue Mountains canyon to find the fossils alive and well and the Wollemi pine was reborn.

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'Dinosaur' tree's secret survival plan

In a secret grove, a population of replanted wild Wollemi Pines is isolated from the original Wollemi Colony.

At the time of its discovery the then director of the Royal Botanic Garden, Professor Carrick Chambers, said: "The discovery is the equivalent of finding a small dinosaur still alive on Earth." 

However, fewer than 100 adult trees exist in the wild. It is classified as critically endangered. The Wollemi pine face threats from climate change, illegal harvesting, fire and, most recently, fungal disease.

Its other great handicap is its genetics. Tests on this small isolated population of trees showed no genetic variation whatsoever – and that's bad for species survival.

However, new technology and research have given botanists hope. 

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A study published in October in the Australian Journal of Botany written by Abigail Greenfield and a team of seven scientists found subtle genetic variations in the Wollemi pine population that will help them plan for its long-term survival.

One of the study's authors is Hannah McPherson, from the National Herbarium at the Royal Botanic Garden, Sydney.

"We want to preserve all the genetic variation that's present," she says. "Our findings will help us understand how much of the population we need to transfer to new terrain so the diversity is preserved across the generations."

Translocation of the species is already under trial.

Heidi Zimmer recently completed her PhD on the Wollemi pine. She studied how 191 of the trees coped with translocation to a secret second site near Mount Tomah in the Blue Mountains. Dr Zimmer, now a senior scientist at the NSW Office of Environment and Heritage, says: "These findings should guide us in future translocations to ensure we capture the genetic variation in new sites."

NSW Environment Minister Mark Speakman has welcomed the research. "Knowing that we have different genetic individuals will allow us to select the right mix when we save seeds, propagate plants and prepare new wild sites," he says.

New advances in genomic mapping allowed scientists to find the variation. Previously, DNA sampling took a long time.

Dr McPherson and her colleagues used the latest techniques and equipment available at the Ramaciotti Centre for Genomics at the University of NSW.

"The old techniques were to sequence very small bits of DNA," she says. "So to find the bit that varies between individual plants was like finding a needle in a haystack. The new technique is like generating the whole haystack."

Using a technique called "shotgun sequencing", machines at UNSW skim off the data that is of relevance to the study. The study compared chloroplasts, parts of the plant cell where photosynthesis occurs. Chloroplast has its own DNA. 

Like Mitochondrial DNA in humans, chloroplast DNA allows botanists to study the genealogies of plants. However, whereas mitochondrial DNA is passed on maternally in humans, in many conifers, it is paternal. Initial data from the Wollemi suggests chloroplast is inherited paternally.

"Because the chloroplast is present in many, many copies of the DNA, we can skim it off [the data]. It's only a part of the whole genome, but it's a part that we can easily isolate," Dr McPherson says. "Using this technique we found [genetic] variation that was difficult to find before."

Professor Marc Wilkins runs the Ramaciotti Centre for Genomics at UNSW.  "We use the latest in DNA sequencing technology," he says. "It allows us to generate gigabases [millions of bases] of DNA sequence a day."

"That's the equivalent of tens of human genomes a day." he said.

Dr McPherson extracted chloroplast DNA from the Wollemi for comparison.

Professor Wilkins said: "Chloroplasts are relatively small – about the size of bacteria in terms of DNA. It means we can sequence thousands a day. 

"The accuracy is just astonishing."

Like many conifers and ferns, the Wollemi pine reproduces through a combination of sexual and non-sexual means.  It can make genetic copies of itself and spread through the growth of its vegetative base or it can reproduce sexually with pollen and seeds through its cones.

There are four sites of Wollemi pines at the original location. Dr McPherson and her team identified three different genetic chlorotypes.

​All four strands of tree contained chlorotype 1. Site two had a minor variation in chlorotype 3, which differs from chlorotype 1 by one small variation. The researchers believe this is a mutation.

However, site four has a more significant, if still subtle, genetic variation in chlorotype 2. Of trees at this site there is a 13 per cent presence of this second genetic variation.

Dr Cathy Offord is principal research scientist at the Royal Botanic Garden. Since its discovery in 1994, she has noticed subtle variations in leaf shape between trees and differences in how they responded to propagation techniques. 

"Although we didn't initially find any genetic variation, we knew that with changing technology we would eventually detect differences between the trees," she says. "We noticed that individual trees strike roots differently when we propagate them."

She is endlessly fascinated by the Wollemi. "It's the gift that just keeps giving. We keep finding out more all the time," she says.

"[This discovery] confirms my observations over many years. It also gives me hope that we can find future variations that will help us better manage the plant and look at the future of the expansion of the range of the Wollemi pine."

UPDATE: An earlier version of this story has been amended to include the lead author of the article published in the Australian Journal of Botany.