A new approach to measuring biodiversity has uncovered some biologically important but currently unprotected areas in Western Australia, while confirming the significance of the world heritage listed Wet Tropics rainforests in the country's north-east.

In a paper published in Nature Communications, scientists from CSIRO, University of California, University of Canberra, the Australian Tropical Herbarium at James Cook University and University of New South Wales applied the new method to Australia's iconic Acacia.

The genus Acacia includes Australia's floral emblem the golden wattle, Acacia pycnantha.

"In this study we've taken our newfound knowledge of the genetics of Acacia and its extended family tree and combined it with Australia's comprehensive botanical and environmental databases," explained co-author Dr Andrew Thornhill.

"It's 21st Century botany, using genetics to tell us about Acacia's evolutionary history - its family pedigree."

Lead author Professor Brent Mishler from the University of California, Berkeley, said the approach taken - phylogenetic analysis - gave a much more complex and complete picture of diversity.

"It takes into account not just the number of plant species in an area, but also their rarity in the landscape and the rarity of their close relatives. We're looking at whole branches of the tree of life, rather than just a species out at the end of a branch," he said.

Professor Darren Crayn, Director of the Australian Tropical Herbarium at James Cook University in Cairns, said the research would not have been possible without the decades of groundwork involved in digitising the specimen information held by Australia's herbaria.

"The results of that world-leading collaboration are now shared through public resources like the Atlas of Living Australia and the Australia's Virtual Herbarium," Professor Crayn said.

"It puts us at the forefront, globally, in identifying important areas of biodiversity by combining cutting-edge genetic analysis with the information contained in scientific collections compiled over centuries."

The study involved complex analysis of mountains of data.

"We introduced randomisation to test the accuracy of our calculations, and that made this a massive statistical exercise," Dr Thornhill said. "We used CSIRO's supercomputer to do calculations on the genetics and distribution of around 120,000 recorded plants."

The researchers created a new model to pinpoint areas that are the cradles of new species (neo-endemics) and those where the remaining members of ancient lineages (paleo-endemics) have taken refuge.

The model is called CANAPE, or Categorical Analysis of Neo- and Paleo-Endemism.

"With CANAPE we're looking beyond whether or not a species is rare," Dr Thornhill said.

"We're using the plant's DNA to investigate its evolutionary tree and establish whether it's restricted to a particular area because it's a relatively new species that developed there, or whether this is a previously wide-spread plant that has retreated to the area as its suitable habitat has shrunk.

"That's valuable information for conservation, particularly in light of the pressures of climate change and development."

The study confirms Queensland's Wet Tropics in north-eastern Australia as having high values for paleo-endemism, providing refuge for plants that were probably once more widely distributed across the continent.

"Using CANAPE we've also identified places of Acacia 'super-endemism', where the old and new co-exist - places that are both cradles for new species and refuges for older plants," Dr Thornhill said.

"Some of these extremely significant sites in the north-west of Western Australia are currently unprotected.

"We hope this study, and investigation of other significant plant groups using this new method, will help focus attention on these sites and lead to the conservation of more of the diversity of life on Earth."

Dr Thornhill and his colleagues are now focussing similar studies on Australian eucalypts, conifers and ferns.