An incredibly rare eucalypt found in some of the most densely developed areas of Sydney has been confirmed as a new species.
The yet-to-be formally named species is a shrubby type of eucalypt with cup-shaped fruit and is found in the Hills District in Sydney's north-west.
"It's an unassuming eucalyptus tree," Australian Institute of Botanical Science scientist Trevor Wilson said.
"It's not too tall, it is actually a mallee which means it doesn't have a main trunk system, it looks very shrubby."
It was first spotted in the suburbs in the 1990s, but it is only now that scientists can say with certainty that it is a distinctive new species.
"It's been a long time coming," Dr Wilson said.
To answer that question, the Australian Institute of Botanical Science used genomic sequencing to identify key differences from other types of eucalypt and understand more about its evolutionary history.
Dr Wilson said the results showed, not only was it not a hybrid of two other species, it was more distantly-related than expected.
"That means we've identified quite a distinct, more unexpected amount of biodiversity, just sitting at the doorstep of Sydneysiders."
Seedlings to be planted in secret locations
There are estimated to be just 14 populations made up of 700 individual specimens left in Sydney.
"It's never been seen elsewhere outside of Sydney," Dr Wilson said.
"Being close to a lot of urban development and land clearing, it puts something like this in extreme jeopardy."
The species, currently known as Eucalyptus sp.Cattai, was first listed as endangered in 1999 before it was upgraded to critically endangered in 2005.
Now it will get its own name and formal description which scientists hope will boost conservation efforts.
At the Australian Botanic Garden Mount Annan, seedlings are being grown to plant in secret locations.
But many of the seedlings grown from seeds collected from the "Cattai" species turned out to be hybrids.
Given the low number of specimens in the wild, Dr Wilson says it is no wonder that many of the trees have become "frisky" with other species to survive.
Hybridisation is rare in the animal world, but it is quite common between closely-related plant species.
"Eucalypts are notorious for being promiscuous and will readily receive pollen from other eucalypt species.
While it may be a natural phenomenon, scientists want to increase the numbers of the original species.
They are now using genomic sequencing to identify genetically "pure" seedlings to translocate to nearby suitable habitat.
"That's one way we can actually improve the resilience of some of these populations to maximise their survival in the wild," Dr Wilson said.
The institute has partnered with Jiangsu University in China and the NSW government's Saving our Species program to undertake the project.
Dr Samantha Yap, of the Institute's Research Centre for Ecosystem Resilience, said confirmation that it was a distinct species was significant.
She said genetic studies were increasingly being used to overcome some of the roadblocks in the way of species discovery.
"For effective conservation, the first step should be to assess what's a rare species and what is not, and a genetic study presents a very effective approach," she said.
