Undocumented plant extinctions are a big problem in Australia – here’s why they go unnoticed



Matchstick banksia (Banksia cuneate). There are only about 500 of these plants left in the wild at 11 different sites, with much of its habitat having been historically cleared for agriculture.
Andrew Crawford/Threatened Species Hub

David Coates, University of Western Australia

A recent survey on the world’s plants found a shocking number have gone extinct – 571 since 1750. And this is likely to be a stark underestimate. Not all plants have been discovered, so it’s likely other plants have gone extinct before researchers know they’re at risk, or even know they exist.

In Australia, the situation is just as dire. The Threatened Species Recovery Hub recently conducted two evaluations that aren’t yet published of extinct plants in Australia. They found 38 have been lost over the last 170 years, such as the Daintree River banana (Musa fitzalanii) and the fringed spider-orchid (Caladenia thysanochila).




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But uncertainty about the number of plant extinctions, in addition to the 38 confirmed, is an ongoing concern.

Both studies pointed out the actual number of extinctions is likely to be far more than those recognised in formal lists produced by the Commonwealth and state and territory agencies.

For example, there is still a high rate of discovery of new plant species in Australia. More than 1,600 plants were discovered between 2009 and 2015, and an estimated 10% are still yet to be discovered.

The extinction of Australian plants is considered most likely to have occurred in areas where there has been major loss and degradation of native bushland. This includes significant areas in southern Australia that have been cleared for agriculture and intensive urbanisation around major cities.

Many of these extinct plants would have had very restricted geographic ranges. And botanical collections were limited across many parts of Australia before broad scale land clearing and habitat change.

Why extinction goes undocumented

There is already one well recognised Australian plant extinction, a shrub in Phillip Island (Streblorrhiza speciosa), which was never formally recognised on any Australian threatened species list.

Black magic grevillea (Grevilla calliantha) is known from only six populations within a range of 8 square kilometres. In the wild the species is threatened by frequent fire, habitat loss, invasive weeds, herbicide overspray, grazing animals and phytophthora dieback.
Dave Coates

Researchers also note there are Australian plants that are not listed as extinct, but have not been collected for 50 years or more.

While undocumented extinction is an increasing concern, the recent re-assessment of current lists of extinct plants has provided a more positive outcome.

The re-assessment found a number of plants previously considered to be extinct are not actually extinct. This includes plants that have been re-discovered since 1980, and where there has been confusion over plant names. Diel’s wattle (Acacia prismifolia), for instance, was recently rediscovered in Western Australia.




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A significant challenge for accurately assessing plant extinction relates to the difficulties in surveying and detecting them in the Australian landscapes.

Many have histories associated with fire or some other disturbance. For example, a number of plants spend a significant part of their time as long-lived seeds – sometimes for decades – in the soil with nothing visible above ground, and with plants only appearing for a few years after a fire.

But by far, the greatest reason for the lack of information is the shortage of field surveys of the rare plants, and the availability of botanists and qualified biologists to survey suitable habitat and accurately identify the plants.

Purple-wood wattle (Acacia carneorum) is slow growing and rarely produces viable seed. Threats are not well understood but grazing by livestock and rabbits is likely to impact on the species.
Andrew Denham

What we’ve learnt

The continuing decline of Australia’s threatened plants suggests more extinctions are likely. But there have been important achievements and lessons learnt in dealing with the main causes of loss of native vegetation.

Our understanding of plant extinction processes – such as habitat loss, habitat degradation, invasive weeds, urbanisation, disease and climate change – is improving. But there is still a significant way to go.




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One challenge in dealing with the causes of Australian plant extinction is how to manage introduced diseases.

Two plant diseases in particular are of major concern: Phytophthora dieback, a soil-borne water mould pathogen, and Myrtle rust, which is spread naturally by wind and water.

Both diseases are increasingly recognised as threats, not only because of the impact they are already having on diverse native plant communities and many rare species, but also because of the difficulties in effective control.

Two Australian rainforest tree species Rhodomyrtus psidioides and Rhodamnia rubescens were recently listed as threatened under the NSW legislation because of myrtle rust.

Native guava (Rhodomyrtus psidioides) A tree species around the margins of rainforest between the NSW and the QLD border. The species is has now been listed as Critically Endangered. Surveys of rainforest areas infected with Myrtle Rust found that 50 to 95% of native guava trees were killed by the disease within a few years.
Zaareo/Wikimedia

While extinction associated with disease is often rapid, some individual plants may survive for decades in highly degraded landscapes, such as long-lived woody shrubs and trees. These plants will ultimately go extinct, and this is often difficult to communicate to the public.

While individual species will continue to persist for many years in highly disturbed and fragmented landscapes, there is little or no reproduction. And with their populations restricted to extremely small patches of bush, they’re vulnerable to ongoing degradation.




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In many such cases there is an “extinction debt”, where it may take decades for extinction to occur, depending on the longevity of the plants involved.

But it’s not all doom and gloom. A recent study found of the 418 threatened Australian plants showing ongoing decline, 83% were assessed as having medium to high potential for bouncing back.

And with long-term investment and research there are good prospects of saving the majority of these plants.The Conversation

David Coates, Adjunct Professor and Research Associate, University of Western Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Built like buildings, boab trees are life-savers with a chequered past



A boab tree in the Kimberley. Boab trees can live for thousands of years and their trunks hollow out as they get older.
Shutterstock

Gregory Moore, University of Melbourne

Sign up to the Beating Around the Bush newsletter here, and suggest a plant we should cover at batb@theconversation.edu.au.


When you are in the northern part of Western Australia, one of nature’s joys is seeing a large boab tree close up, perhaps for the first time.

The boab (Adansonia gregorii) is a native to this part of Australia, but is related to the broader group of species called boababs that live in Madagascar and Africa – but more on that connection later.

Boabs are also called bottle trees, the tree of life, boababs and Australian boababs. Some of the indigenous Australian names include gadawon and larrgadi.

From their iconic swollen trunks, to living up to 2,000 years and the many uses for their “superfood” fruits, here’s what makes boab trees so fascinating.



The Conversation

The ‘upside-down tree’: trunks that save lives and lock up prisoners

While the boab in Australia is not quite as well-documented as the African species, specimens have been recorded at over 1,000 years of age. Some living trees have been estimated to be nearer to 2,000 years old.

And while it’s difficult to age the trees, several specimens of the African species have been dated at 2,000 or more years old.

Australian boabs can grow up to 15 metres tall at maturity and have swollen, attention-grabbing trunks called a caudex, which may be up to five metres in diameter.

The African boab species, A. digitata, can be much taller, at 25 metres high and with a diameter of up to 15 metres.




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In such dry continents, the caudex is a life-saver, often containing water, which was tapped by Indigenous folk. It has been estimated that some of these huge old trees can hold more than 100,000 litres of water in their trunks.

In Africa, these massive trunks have been used as shelters, homes, farm sheds and, more recently, even shops and bars.

Sadly in Australia, legend has it the huge trunks were used to make lock-ups for Indigenous people and other prisoners.

The infamous Boab Prison Tree, just south of Derby in Western Australia, was said to have once held Indigenous prisoners.
Shutterstock

It’s not just the trunk that can stop you in your tracks. The boab has a unique branching structure, one that looks more like a root system than a canopy.

Some locals in Africa will tell you the tree was dropped from heaven to earth and landed upside down. So the African species of boab is sometimes called the upside-down tree.

Boab fruits are ‘superfoods’ and its shell has many uses

A. gregorii, the Australian boab species, has large, attractive white flowers up to 75 millimetres in length. Its round fruits are edible and sought after by birds, mammals and humans. The fruit gives rise to some of the common names for the tree, such as monkey bread tree and dead rat tree. The latter comes from the appearance of older fruits in the canopy looking a bit like … well, dead rats?




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In fact, there’s great interest in fruits from the African species, A. digitata, which are considered a “superfood” because of their high levels of antioxidants, calcium, potassium, magnesium, fibre and vitamin C. It’s assumed many of these traits will be shared by the Australian boab, but there is little research as yet to prove it.

Fruit of the African boab tree fruit are initially covered in velvety fur.
Ton Rulkens/Wikimedia, CC BY-SA

The soft part of the fruit is surrounded by a hard, coconut-like shell that’s initially covered in a velvety fur. The hard shell has been used for cups and bowls, but has also been intricately carved and decorated by Aboriginal artists in Africa and Australia. If the seeds are left inside the fruit as it dries, they can be used for toys like rattles.

On both continents, Aboriginal people have eaten the white powder that surrounds the seeds. The leaves are rich in iron and the pulp from the fruits tastes like cream of tartar.

The Indigenous people of both continents were also well aware of the medicinal uses of the fruits. The bark and leaves of the trees also treat various ailments, but particularly those associated with digestive disorders.




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But at present there is very little modern research on the medicinal and dietary aspects of either the baobab or boab.

How the boab tree got to Australia

One of the mysteries surrounding the boab is how it got to Australia – the Australian species has clear affinities with related species in continental Africa and Madagascar.

A baobab tree, Adansonia digitata, in Tarangire National Park, Tanzania. Its journey from Africa to Australia remains a mystery.
Yoki/Wikimedia, CC BY-SA

There are three intriguing theories.

The first is that all of the boababs originate from the super-continent Gondwana – consisting of Africa, South America, Antarctica, Australia, India and Madagascar – before it fragmented almost 80 million years ago. But A. Gregorii and A. digitata are so similar genetically that, given the millions of years that have elapsed, this theory is now in question.

The second theory comes from recent DNA analysis of the species. It suggests they separated more recently, perhaps only 70,000 years ago, which raises the question, were humans involved in their journey? But did they come to Australia from Africa, or from Australia to Africa? The latter is a less likely scenario given the direction of ocean currents.

And the third theory is that fruits arrived on the Australian shore after an epic ocean voyage from Africa.




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Boabs are usually found in the remote outback of Australia, but in 2008, a large 750-year-old boab was transported from Warmun in the Kimberley to Perth and transplanted in Kings Park.

Transplanting such a large tree is both daunting and fraught, with a high chance of failure, but the deciduousness and growth habit of the boab gave some cause for optimism about a successful outcome. For the reward of having a large old boab growing in Perth, it would be worth it.

After a period of stress, the tree appears to be coming good, reflecting the toughness of the species.

A large, mature boab is a splendid tree of arid Australia that inspires awe in all who experience them close up. They really are a beauty and a bottler of a tree!


Sign up to Beating Around the Bush, a series that profiles native plants: part gardening column, part dispatches from country, entirely Australian.The Conversation

Gregory Moore, Doctor of Botany, University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.

This centuries-old river red gum is a local legend – here’s why it’s worth fighting for


Euan Ritchie, Deakin University

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In Dr Seuss’s The Lorax, his titular character famously said:

I am the Lorax. I speak for the trees. I speak for the trees, for the trees have no tongues.

In the midst of a global extinction crisis, the Lorax’s call to preserve what is precious couldn’t be more apt. The greatest threat to the survival of species globally continues to be habitat destruction and modification.




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A potential and local victim of this ongoing environmental catastrophe is a single tree, and a tree I have a deep personal connection with. The tree I refer to is Bulleen’s iconic 300-year-old river red gum (Eucalyptus camaldulensis).

To me this tree has been a constant in my life. While everything else has changed around me, it has stood there, solid, just as solid as its red gum fibres are known to be.

As a child I fondly remember looking up at this tree in awe, as we’d often stop at the nearby service station on a hot summer’s day to buy a cold drink or ice-cream on the way to Saturday sport, the nearby Birrarung (Yarra River), or my grandmother’s house.



The Conversation

Bulleen’s majestic river red gum

It’s estimated to be approximately 20 metres in height with a canopy spread of 17 metres. And its trunk measures a whopping two metres across.

The tree is thought to be the oldest remnant of a once substantial red gum forest, and was saved by a local resident when the rest of the area was cleared for the construction of a service station.

It now faces destruction, as it is within the preferred path of construction for Victoria’s North East link.




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While the measurements of this tree are impressive, the splendour and value for me is that it has survived for so long and, in more recent times, against tremendous odds.

Surviving against all odds

The Bulleen red gum stands beside one of Melbourne’s busiest roads and the immediate area is covered with concrete and bitumen. The tree’s roots and health have therefore been challenged for a long time, and yet this massive red gum stands, as if in defiance of the modern world and the development that has encircled it.

Since this tree has survived for so long, it undoubtedly holds a special connection with so many: the Wurundjeri-willam people of the Kulin Nation, members of Australia’s famed Heidelberg school of artists who lived and worked in the near vicinty, everyday commuters that have driven or walked by or stopped to admire it, or the war verteran Nevin Phillips who once apparently defended it with his rifle against it being chainsawed.

Very old trees such as Bulleen’s river red gum deserve our respect and protection, for these trees have substantial environmental, economic and cultural value.
National Trust

Further proof of the value of this tree to so many is that it was awarded The National Trust of Australia’s (Victoria) 2019 Victorian Tree of the Year.

Why we must speak for and save old trees

I grew up near this tree and, like the Lorax, I would like to speak for it.
Trees as old as the Bulleen river red gum are now increasingly rare in our world, and beyond their strong personal and cultural values, including in some places as Aboriginal birthing sites, they are tremendously important for other reasons as well.




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These trees provide shade and help keep our cities cooler, improve our mental health and wellbeing, and store considerable amounts of carbon aiding our fight against climate change.

Perhaps most importantly, under their bark and in their cracks and hollows, they provide homes for many of Australia’s precious but increasingly imperilled native wildlife, including bats, birds, possums and gliders, snakes and lizards, insects and spiders.

These homes are prime wildlife real estate, especially in our big cities, where such large old trees are vanishingly rare but where considerable wildlife, common and threatened, still persists. And yet more could survive with a helping hand from us.

A powerful owl chick in a tree hollow, in outer Melbourne.
John White (Deakin University)

As cities like Melbourne continue to grow around the world, there will be more and more cases where arguments of progress are used to justify the further destruction of what nature remains. But progress shouldn’t come at any cost, and in the case of preserving iconic and valuable trees such as Bulleen’s river red gum, it would seem there’s more than enough reasons to ensure this tree’s life and its many values continue.

Perhaps again the wise sage, the Lorax, says it best.

Unless someone like you cares a whole awful lot, Nothing is going to get better. It’s not.


Sign up to Beating Around the Bush, a series that profiles native plants: part gardening column, part dispatches from country, entirely Australian.The Conversation

Euan Ritchie, Associate Professor in Wildlife Ecology and Conservation, Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Meet the Kakadu plum: an international superfood thousands of years in the making


Greg Leach, Charles Darwin University

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The Kakadu Plum fruiting season in the Top End is just finishing. Over one weekend, I was able to find a few fruits on the ground beneath some trees in the Eucalypt woodland near Darwin.

This is the best way to eat Kakadu plums – fresh, fully ripe, and fallen from the tree. The fruit is smooth, fleshy and ovoid in shape with a short beak, and yellow–green or slightly reddish when ripe.

Initially, the taste seems somewhat bland, but with a definite sour and astringent finish. While that’s probably not a very inspiring description to encourage a tasting, a professional flavour profile describes the taste as “a stewed apple and pear aroma with cooked citrus and a floral-musk note” – so it’s perfect for jam, sauces and relishes.




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With small, creamy white flowers in long spikes clustered towards the tips of the branches, the Kakadu plum, Terminalia ferdiandiana, is just one of about 29 species of Terminalia found in Australia.

But the extraordinary properties of the Kakadu plum makes it attractive for a diversity of food, beverage and even cosmetic products. And this demand is creating supply problems as competition to cash in on the fruit increases.



The Conversation

A plum by any other name

Kakadu plums are abundant in the Eucalypt woodlands of the northern savannas. There are a plethora of Aboriginal names that reflect the distribution of the species and the broadly held knowledge across numerous language groups, such as “Gubinge”, a name from the Bardi people north of Broome.

Common names such as “billygoat plum” or “green plum” are also sometimes used. But thanks to marketing success, the common name “Kakadu plum” is the most well known, although it’s misleading.

While the species is found in Kakadu National Park, its distribution extends to the savanna vegetation, from the Kimberley to Cape York.

Getting ‘superfood’ status

The rise of the Kakadu plum to international fame as a “superfood” may appear to have come about almost overnight. But this story has been a long time in the making.

Aboriginal people have valued this plant for thousands of years for its food and medicinal properties. The health benefits of the fruit were certainly recognised, but more specifically, the red inner bark was used to treat skin conditions and sores.




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The findings of western scientists also go back a little way. Pioneering analysis of the composition of bush foods in the early 1980s found phenomenally high vitamin C content in Kakadu plums.

Citrus fruits are known for being good natural sources of vitamin C, which makes up around 0.5% of their weight.

But the Kakadu plum tops the scale, with vitamin C levels of 3.5-5.9% of its weight. This is about 50 times more vitamin C than in oranges.

Chemicals in the plum also have antioxidant, anti-inflammatory and antimicrobial properties, and recent research has shown extracts have excellent preservative qualities. This means the plum is now used in the seafood industry to extend the shelf life of, for instance, cooked prawns.

Opportunities for Indigenous-owned business

Now, increased demand for the fruit has produced opportunities for Indigenous communities to create enterprise on country.

Many communities in the Top End and the Kimberley are now engaged in fruit harvesting, which, for the most part, takes place from the wild on Indigenous-owned land.

A successful example is in Wadeye, about 250km southwest of Darwin.

I spoke to the Community Development Officer at Thamarrurr Development Corporation there, Melissa Bentivoglio, who said:

Thamarrurr Plums [Kakadu plums], based at Wadeye, has been evolving over the past 10 years as a locally owned and operated Indigenous enterprise. This year’s plum season saw over 250 local women harvest over 10 tonnes of plums from their clan estates in the Thamarrurr Region.

The community continue to carefully discern their way forward in this local enterprise to ensure community ownership and long-term sustainability.

But Indigenous representation over the entire supply chain and processing is poor. The participation rate in the bush food industry is reported to be less than 1%.

Indigenous groups are actively seeking mechanisms to see greater recognition and returns from their traditional knowledge.

In 2007, for instance, the American-based cosmetic company Mary Kay Inc. was granted a patent for Kakadu plum extracts in a skin cosmetic product.




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These patents were opposed following concerns around the recognition of the Indigenous knowledge and the lack of any benefit-sharing arrangements with relevant Indigenous communities. They were rejected by IP Australia on the grounds of lack of novelty – there were serious claims of biopiracy – commericially exploiting natural material – a cloud of uncertainty around the legal acquisition of the plant material.

Competing interests: food, cosmetics, bandicoots

The increasing demand for the fruit and sustainability concerns of the harvest has led the Northern Territory government to draft a management plan for Kakadu plum. It was released for public comment last year.

Ecologists also know the fruits of Kakadu plum form an important part of the diet of a suite of small native mammals, such as possums, rock rats, tree rats, and bandicoots. The recently observed decline in these populations can, in part, be attributed to overly frequent fires which are detrimental to small trees in the wild like the Kakadu plum.

The NT government’s management plan will need to ensure commercial harvest doesn’t add to the pressure on these native mammals.




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What’s more, the traditional medicinal uses are being tested in a current research project through a Cooperative Research Centre for Developing Northern Australia (CRCNA) funded collaboration to assess potential for establishing a medicinal plant agribusiness on Indigenous land.

It’s not easy being a super plant.


Sign up to Beating Around the Bush, a series that profiles native plants: part gardening column, part dispatches from country, entirely Australian.The Conversation

Greg Leach, Honorary Fellow at Menzies School of Health Research, Charles Darwin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

How I discovered the Dalveen Blue Box, a rare eucalypt species with a sweet, fruity smell



Tim Collins classifying a new species of eucalyptus tree, Eucalytus dalveenica, March 2019.
University of New England, Author provided (No reuse)

Tim Collins, University of New England

Sign up to the Beating Around the Bush newsletter here, and suggest a plant we should cover at batb@theconversation.edu.au.


In 2002, I went on a bushwalk with plant taxonomist David Albrecht, and had a big surprise. He pointed to a plant I thought I knew, and said: “that’s probably a new species.”

A new species? How could it be that this plant had not already been scientifically described and named?

I was in for another surprise when I learnt there are estimated to be thousands of undescribed plant species in Australia. But just because one botanist says a plant is a new species, it doesn’t mean that everyone else automatically agrees.

As a researcher, I had the opportunity to study one of Australia’s most iconic plant groups – the eucalypts.

Herbarium records of an endagered eucalyptus species, the Northern Blue Box (Eucalyptus magnificata), showed populations from the Northern Tablelands in New South Wales scattered up to the Granite Belt in southern Queensland.



The Conversation

But on closer inspection, I discovered there were different ecosystems between populations. E. magnificata, for instance, is found on rims of gorges in Oxley Wild Rivers National Park, whereas E. baueriana is typically found on riverbanks and flood plains.

The question I wanted answered was: are all these populations really E. magnificata or have some been misidentified and represent other common species? Or, alternatively, are they new, undescribed rarer species?

So when my supervisors, Professor Jeremy Bruhl and Dr Rose Andrew, and I visited the mystery trees near Dalveen in southern Queensland, we knew immediately they were something exciting. They just looked different to everything else we’d seen.

Eucalyptus that smells sweet and fruity

To find out, I’d been sampling eucalyptus (collecting, pressing and drying specimens) and had spent the past two days with my supervisors. With our heads craned back, we stared through binoculars to search the tree canopy at dozens of sites on the Northern Tablelands looking for the buds and fruits that enable eucalypt identification.

Not only did these trees at Dalveen look unlike anything else we’d seen on the trip, they also had a different smell. When we crushed a leaf, the aroma was sweet, mild and fruity, quite unlike the familiar eucalyptus oil.

Back at the university, I could compare the different collections. I examined and recorded differences in the size and shapes of the leaves, buds and fruits. I grew seedlings of my field collections and saw that seedling leaves were also consistently different.

And I extracted the mixture of aromatic chemicals in the leaf oils collected during fieldwork. Then, I used a chemistry laboratory technique, called Gas Chromatography Mass Spectrometry, to compare their concentrations with closely related species, such as E. baueriana and E. polyanthemos.

The results clearly explained why the leaves had a unique scent. That sweet and fruity aroma was due to larger molecules, called sesquiterpenes, which dominated the leaf-oil. There were only traces of the familiar-smelling cineole molecule common to most eucalypts.

A new species, or just an uninhibited sex romp?

Sequencing the DNA of the tree added another piece to the puzzle.

We had collected samples from all of the closely related common species. We had strong evidence from the shape of the leaves, fruits and flower buds suggesting the Dalveen trees were different. But the possibility remained that they were just hybrids.

Eucalyptus trees can be wickedly promiscuous and hybrid trees with similar characteristics are common. In some parts of eastern Australia, for instance, eucalypts naturally form hybrid swarms, the botanical equivalent of a wildly uninhibited sex romp!

But the DNA told us the trees from Dalveen were genetically distinct, and with no suggestion of shared ancestry.

Now, with three very different data sets all supporting the same conclusion, it became imperative we publish our findings and describe the new species, which we named Eucalyptus dalveenica, or the Dalveen Blue Box.

New species have to be named using a universal and internationally accepted naming system. Names and descriptions must be published, and a pressed and dried specimen must be nominated to be the representative that other collections can be compared to.

Most importantly, convincing evidence must be presented that persuades the botanical community the newly named species should be accepted.

But naming a new species is only the first step in knowing what it is. Importantly, naming tells us what it isn’t. The trees at Dalveen are not Eucalyptus magnificata, nor do they belong to another more common species, E. baueriana or E. conica.

Eucalyptus dalveenica is a rare and endangered part of Australia’s natural heritage. Taxonomic description of new species (classifying, describing and naming) provides the framework for ongoing accurate identification, species conservation and further study.

We are fortunate to live in a beautiful part of the world, with diverse and unique wildlife. Describing biodiversity and communicating new discoveries develops connections between people and their local environment, leading to a broader understanding of our home.


Sign up to Beating Around the Bush, a series that profiles native plants: part gardening column, part dispatches from country, entirely Australian.The Conversation

Tim Collins, PhD candidate , University of New England

This article is republished from The Conversation under a Creative Commons license. Read the original article.

How I stumbled on a lost plant just north of Antarctica


Nick Fitzgerald, University of Tasmania

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Sunny interludes punctuate showers of rain, hail and sleet as furious winds sweep clouds across the sky. It’s a typical summer day on Macquarie Island, a sliver of ocean floor that rose more than 2.5 km from the depths of the Southern Ocean, halfway between Tasmania and Antarctica, around 12 million years ago.

On this February day in 2013, my colleague Jennie Whinam and I are visiting monitoring sites for the critically endangered Macquarie Island cushion plant, Azorella macquariensis, which has been suffering extensive dieback.

It is a short walk from our cosy field hut to Skua Lake on the opposite side of the island – a mere four kilometres of steep off-track walking, head-first into the icy wind.

We make a small detour to the shoreline of Skua Lake, the only known location for perhaps the rarest plant on the island, the subantarctic bedstraw (Galium antarcticum). This small herb had not been seen since it was first recorded on Macquarie Island in the early 1980s, despite several searches in the subsequent 30 years.



The Conversation

It seemed likely the humble bedstraw was extinct on Macquarie Island, and we weren’t confident we’d see one that day. It is a small herb, growing to a few centimetres in size, with reddish leaves clustered on sprawling stems and tiny inconspicuous white flowers. Not the easiest plant to spot amongst the lush growth of a subantarctic meadow.

But within five minutes of arriving at the shoreline of Skua Lake, we spotted a reddish-coloured herb unlike any other plant there, partly hidden among dense mosses and grasses.

Excitedly, we set about searching for others, finding hundreds of the tiny plants!

But our celebratory feeling was soon blown away by a flurry of horizontal snow carried across the lake. Skua Lake is perched on the top of an escarpment 130 metres above the ocean with no shelter from the winds that travel unimpeded around the globe at these latitudes.

We were so cold we had to start moving again. And turning our backs to the wind, we marched across grassy hills dusted with fresh snow.

Hidden for three decades

Our rediscovery of this critically endangered species raised a couple of questions. Where had it been hiding for 30 years? And, given the abundance of apparently suitable habitat on the island, why was it restricted to one location?

These questions remain unanswered. But four years later, in 2017, botanists Cath Dickson and Alex Fergus stumbled upon a second population of subantarctic bedstraw on the opposite side of Skua Lake, comprising an estimated 1,000 plants. But why it is not even more widespread remains a mystery.

Perhaps the bedstraw was preferentially grazed by invasive rabbits, which have had a dramatic impact on the vegetation of Macquarie Island. Or, the plant could be a recent immigrant to the island yet to expand its range.

Galium is a large and widespread genus of herbs (commonly called bedstraw) in the Rubiaceae family, with several native and introduced species in Australia including the familiar garden weed cleavers or sticky weed. Many species have distinctive bristly hairs, whereas G. antarcticum is hairless.

With a total known population of 1,500 plants confined to a few square metres of windswept tundra, Galium antarcticum remains critically endangered in Australia.

Travelled across vast seas

Macquarie Island is a young and very remote landmass with an unusual cold maritime climate. Its flora was born from long-distance dispersal and largely composed of subantarctic specialists.

Subantarctic bedstraw is one such specialist, and is also found in Patagonia, South Georgia, the Falklands, Crozet and Kerguelen islands. This wide distribution throughout most of the Subantarctic, including islands separated by thousands of kilometres of ocean, suggests this species has been dispersed by seabirds.

The future prospects for the species on Macquarie Island are uncertain. It may benefit from the recent eradication of rabbits, expanding its range, or it may struggle to compete with taller growing plants as the short grassland transitions to a more closed vegetation community in the absence of grazing pressure. Or it may continue to be a mystery.


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Nick Fitzgerald, PhD candidate, University of Tasmania

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Vic Stockwell’s Puzzle is an unlikely survivor from a different epoch


Andrew Thornhill, University of Adelaide

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On the western side of Mount Bartle Frere, the tallest mountain in Queensland, grows a tree that shares an ancient link to Australia’s most dominant plant group.

To get there, you must find a track hidden by rainforest and then walk for around an hour up and down a dirt path, until you reach cathedral-like giant red barked trees. This is Stockwellia quadrifida, also known as “Vic Stockwell’s puzzle”: a close but anciently separated relative of the eucalypts.




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This ancient tree is best suited for wetter and warmer environments, a throwback to when this continent was still connected to South America and Antarctica 40-50 million years ago, in the supercontinent Gondwana.

But this rare plant is now at risk by an introduced threat, myrtle rust, a plant disease that was accidentally introduced to Australia from South America.


Photos courtesy of Stuart Worboys and CSIRO.


Sister to the eucalypts

In my opinion, Stockwellia trees are in the same league as California Redwoods – they’re both old, with very few close living relatives. In fact, they are probably more special, as only around 400 Stockwellia trees remain.

Some of the trees I saw in Queensland have large buttressed roots and are hollowed out so you can walk inside the tree and stare upwards. Their bark is strikingly red, and their enormous size means you have to crane your neck to see the top.

Stockwellia takes its name from a Queensland forest ranger named Victor Stockwell who worked in the Boonjee area on Mount Bartle Frere where the trees grow. While the species wasn’t officially scientifically described until 2002, it had been known to botanists for many decades.

The trees were first identified using aerial photography. For Vic Stockwell, the tree was a “puzzle” because despite his vast experience in the forests of Far North Queensland, he was surprised to come across a species of tree he didn’t recognise.

Ancient rainforest groups

In the early 2000s, a DNA study found Stockwellia belonged to a group of rainforest trees called the “mesicalypts”, a name coined by my colleagues and I.

Mesicalypts are a sister group to Australian eucalypts, and are made up of four species of rainforest plants, including Stockwellia. Eucalypts, on the other hand, have more than 800 species growing all over Australia, in much drier conditions.

DNA results suggest there is also another evolutionary group in between mesicalypts and eucalypts which only grows in New Caledonia, a species called Arillastrum gummifera. We have informally named this single species group “newcalypt” – New Cal-(edonian) (eucal)-ypt – because we didn’t want to make it feel left out from getting a new informal name.


The Conversation/Andrew Thornhill

Puzzling history

Molecular dating of these groups revealed some even more enigmatic things about the divergence of the mesicalypts and the newcalypt from the eucalypts.

The sole New Caledonian species is estimated to have had a common ancestor with the eucalypts around 59 million years ago. This poses an interesting question. How did a plant that old end up on a land mass that we think is only 30 million years old?

We don’t really know yet, and botanists still debate about where it came from and how it got there.




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Mesicalypts are also around 60 million years old and we estimate Stockwellia diverged from its nearest living relative around 30-40 million years ago. This was in an epoch called the late Eocene when the world was much wetter and warmer, and when Australia was still connected to South America and Antarctica.

With no fossil record of any ancient mesicalypts, it’s unclear how diverse and widespread they were back then. If we assume more species of mesicalypts once existed, then the ones we see today are the last living survivors from a very different past.

Their history is also the tale of two different fortunes.

The mesicalypts are better suited to live in wetter and warmer environments, and their relatives – the eucalypts – are better suited to drier and hotter conditions.

When Gondwana finally split and Australia started drifting north, one group had to hang on as their suitable growing conditions began to shrink, while the other hit the jackpot and became the dominant vegetation of the continent.

An extinction threat

Once, the main threat to the small number of Stockwellia populations appeared to be only white cockatoos eating their seeds.

But now they are menaced by something more sinister than birds. More than a decade after the species was officially named, I was taken to see the Stockwellia by Stuart Worboys from the Australian Tropical Herbarium.




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Invasive species are Australia’s number-one extinction threat


On this trip Stu found leaves of Stockwellia with myrtle rust on them – the first such recording for the tree.

Myrtle rust is a disease of the Myrtaceae family, and was accidentally introduced from South America in the late 2000s. It attacks plant leaves, fruit and, in some cases, kills the plant outright.

The Australian Myrtaceae have had no time to adapt to myrtle rust. What is happening now could cause the extinction of some extremely unique Australian plants – including Stockwellia.

It is sad to think a plant group that has hung on for so long, in a secluded part of Australia, minding its own business, now faces an introduced threat.

The hunch is that the myrtle rust was introduced to Stockwellia from the shoes of one of its human visitors. Unfortunately, we may have loved the tree to death.

Let’s hope it’s tough enough to withstand the rust and live for many more millions of years. If it is lost, it would take with it 40 million years worth of evolutionary history in Myrtaceae. And after surviving so much tumultuous history of changing continental climates, cyclones, and everything else that a tropical environment could throw at it, that would be a very sad thing.


Sign up to Beating Around the Bush, a series that profiles native plants: part gardening column, part dispatches from country, entirely Australian.The Conversation

Andrew Thornhill, Research botanist at the Botanic Gardens and State Herbarium of South Australia/Environment Institute, University of Adelaide

This article is republished from The Conversation under a Creative Commons license. Read the original article.