The meat-eating bladderwort traps aquatic animals at lightning speed



A hapless animal will swim by, triggering the sensitive hairs at the front of the bladderworts’ bladder, which open like a trap door.
Emma Lupin, Author provided

Greg Leach, Charles Darwin University

Carnivorous plants intrigue people. It’s so out of place to our mental image of what “normal” plants should do.

On the outskirts of Darwin, bladderworts can be found feasting on aquatic animals such as invertebrates, insect larvae, aquatic worms, and water fleas.




Read more:
The Albany pitcher plant will straight up eat you (if you’re an ant)


A hapless animal will swim by, triggering the sensitive hairs at the front of the bladderwort’s bladder, which opens like a trap door. The rush of water into the trap carries the animal inside. The door slams shut and digestion starts.

This all happens faster than the eye can see – in less than a millisecond, more than 100 times faster than a Venus flytrap.



The Conversation

The best habitat in all the (wet)land

The bladderwort is just one example of Utricularia. Australia’s Top End contains some 36 species of Utricularia, making it a a global centre for the genus. And the species count is still going up as researchers make new discoveries.

In particular, bladderworts can be found around the Howard River, about 30km east of Darwin, part of a 264 square km area of significant conservation value.




Read more:
Rising seas allow coastal wetlands to store more carbon


The Howard River area supports the largest and most continuous stretch of seasonally-flooded sandy wetlands in the Northern Territory, with extensive shallow lagoons and swamps.

The layer of fine sand is between 1 and 10 metres thick. The sand overlays less permeable material such as rock and clay, so the sand becomes completely waterlogged in the wet season. It makes a perfect home for bladderworts.

This highly dynamic environment provides a miniature topography of rises and depressions measured in just centimetres. As well as the alternating monsoonal dry and wet seasons, the topography is overlain with seasonal changes in water levels.




Read more:
The waterwheel plant is a carnivorous, underwater snap-trap


The species of Utricularia have adapted to different windows of opportunity in these seasonal changes and partition themselves within the habitat, often based on water height.

Within the same small area, species come and go during the season based on their tolerance of these habitat variables. This can be frustrating for the collector and observer, as not all species are found at the one time.

All shapes and sizes

A unifying feature of the Utricularia genus is the suction trap – or “bladder”. But the bladderwort species come in many shapes and sizes.

Flowers, for instance, can vary in size. Some bladderworts have flowers with large nectar-filled spurs. These can grow up to 15 millimetres long and attract insects with a long proboscis (an elongated “snout”). Other bizarre flowers on different bladderwort species have long antennae-like extensions and appear to involve insect mimicry to attract pollinators.




Read more:
Squid team finds high species diversity off Kermadec Islands, part of stalled marine reserve proposal


Other bladderwort species, such as U. odorata, have tall, conspicuous groups of flowers up to 70cm high, with up to 20 bright golden yellow flowers.

And aquatic species of bladderwort have, in some cases, even developed floats around the flowering stalk to keep the flowers above water.

Threats to the Howard Sand Plains

But all is not well on the Howard Sand Plains. The unique landscape is under threat from urban development, recreational misuse, fire, and weed encroachment.

But construction booms in Darwin have created added pressure on the Sand Plains.




Read more:
Can we really restore or protect natural habitats to ‘offset’ those we destroy?


Twenty-two per cent of the sand sheet landscape in this region has been cleared for sand mining, as it holds a huge source of easily accessible, fine, high-grade sand used in concrete for building.

But it’s not all doom and gloom. A project, “Secret World: Carnivorous plants of the Howard sand sheets”, brought artists and scientists out into the field in a workshop setting.

Bladderworts were the inspiration for stunning artworks, leading to education around the species in the local area.
Bladderwort species 1 ….. by John Wolseley/Nomad Art Gallery, Author provided

Scientists explained the significance of the environment, the flora and the threats facing the habitat.

And the artists squelched about the waterlogged habitat and got down and dirty into this Lilliputian world. They set about interpreting the plants and with a diversity of approaches matching the diversity of the bladderworts, they produced a stunning portfolio of artworks.

Artists who explored the waterlogged habitat of the bladderworts produced a stunning portfolio of artworks.
Lunch by Winsome Jobling/Nomad Art Gallery, Author provided



Read more:
More than 28,000 species are officially threatened, with more likely to come


An education kit produced from the project also took the story into local schools.

The Northern Territory Environment Protection Authority assessed the issues and determined areas of the sand sheets that should be set aside for conservation purposes. The art and science collaboration certainly played a pivotal part in this positive conservation outcome.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.

Advertisements

The waterwheel plant is a carnivorous, underwater snap-trap



The whaterwheel plant can snap up its prey in milliseconds.
The Conversation

Adam Cross, Curtin University

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


Billabongs in the northern Kimberley are welcome oases of colour in an otherwise brown landscape. This one reflected the clear blue sky, broken up by water lilies and a scattering of yellow Nymphoides flowers. A ring of trees surrounded it, taking advantage of the permanent water source.

My student and I approached with excitement. We had spent a week searching barren habitats, but now on the final day of our expedition we were ecstatic about the potential of this watering hole.




Read more:
The strange world of the carnivorous plant


Between us we had been plant-hunting in northern Australia for nearly 20 years and knew well that where water seeped over sandstone, carnivorous plants often grew.

Hunting carnivorous plants in the North Kimberley.
Adam Cross, Author provided

Clambering along some rocks at the edge of the billabong, I looked down by chance into a small rockhole and nearly fell in. Floating between two water lily leaves was a short stem of whorled leaves. And at the end of each leaf, a tiny snapping trap.

Looking out into the middle of the billabong I saw thousands of plants, and even a few tiny white flowers protruding above the surface of the water. After a decade of fruitlessly searching the swamps, creeks and rivers of the Kimberley for it, I had stumbled across a new population of Aldrovanda vesiculosa, the waterwheel plant.



The Conversation

The waterwheel plant must surely be among the most fascinating plants in the world. Its genus dates back 50 million years, and although we know of many species from the fossil record, A. vesiculosa is the only modern species.

The waterwheel plant is a submerged aquatic plant, first discovered by botanists in 1696 and studied by the likes of Charles Darwin, and is the only species to have evolved snap-trap carnivory under water. It takes just 100 milliseconds for the snapping leaves to close upon small, unsuspecting aquatic invertebrates such as mosquito larvae – one of the fastest movements in the plant kingdom.

Although the waterwheel plant also photosynthesises, it needs to eat prey to get enough nutrients to grow. And while its traps may be small, up to 1cm long, it can efficiently catch tiny insects and even small fish and tadpoles.

Mr Worldwide

Uniquely, the waterwheel plant is a global clone, with virtually no genetic differentiation between populations on different continents.

It has one of the largest and most disconnected distributions of any flowering species, growing in more than 40 countries across four continents, from sub-Arctic regions of northern Russia to the southern coast of Australia, and from western Africa to the eastern coast of Australia. Yet despite this global distribution, the waterwheel plant occupies a very small ecological niche, and grows only in the shallow and acidic waters of nutrient-poor freshwater swamps.

The waterwheel plant is sensitive, and is often the first species to disappear when these habitats become degraded.

As a result, this unique species has undergone a catastrophic global decline as humans have systematically degraded and destroyed nearly two-thirds of the world’s wetland habitats.

The past century has seen the systematic extinction of the waterwheel plant from more than half the countries it once occupied, and a rapid deterioration in almost all others. From more than 400 populations recorded since the 18th century, fewer than 50 now remain.

Three-quarters of these are in the exclusion zone surrounding the Chernobyl nuclear disaster site, with the rest spread thinly across Africa, Australia and Europe, and isolated from each other by thousands, and sometimes tens of thousands, of kilometres. The species can be seen as a harbinger of the perilous state of our world’s freshwater ecosystems.

Waterwheel plants flourish in this oasis in the remote North Kimberley.
Adam Cross, Author provided

Conservation

Ecologists are working hard at conserving the waterwheel plant: monitoring habitats, reintroducing it into areas where it has become extinct and detailed study of its ecology and reproductive biology.

But ultimately, its future depends on the survival of wetlands – complex and sensitive ecosystems that can be affected by even small changes throughout their catchment area. Wetlands are often linked together by waterbirds and other animals that disperse plant seeds and spores between them, so the degradation of one area can have significant knock-on effects even for distant locations.




Read more:
Why a wetland might not be wet


Without concerted wetland conservation, individual conservation for species like the waterwheel plant become little more than band-aids.

For the waterwheel plant, a single isolated population in a remote and untouched corner of the North Kimberley could represent a crucial refuge. It gives a thin sliver of hope that this remarkable species will still exist for future generations to marvel at.


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

Adam Cross, Research Fellow, Curtin 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

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


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.


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

Nick Fitzgerald, PhD candidate, University of Tasmania

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

Bizarrely distributed and verging on extinction, this ‘mystic’ tree went unidentified for 17 years



File 20190417 139116 1303ckl.png?ixlib=rb 1.1
Flowers of the mystical Hildegardia australiensis. I.D. Cowie, NT Herbarium.
Author provided (No reuse)

Gregory John Leach, Charles Darwin University

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


Almost 30 years ago, the specimen of a weird tree collected in the southern part of Kakadu National Park was packed in my luggage. It was on its way to the mecca of botanical knowledge in London, the Royal Botanic Gardens Kew.

But what was it?

With unusual inflated winged fruits, it flummoxed local botanists who had not seen anything like it before. To crack the tree’s identity, it needed more than the limited resources of the Darwin Herbarium.

Later, we discovered a fragmentary specimen hidden in a small box at the end of a little-visited collection vault in the Darwin Herbarium. And it had been sitting there quietly since 1974.

Most of the specimens inside this box just irritate botanists as being somewhat intractable to identify. It’s known as the “GOK” box, standing for “God Only Knows”.

Together with the resources of Kew Gardens, the species was finally connected with a genus and recognised as a new species.

A year later, it was named Hildegardia australiensis.



The Conversation

Mysterious global distribution

The species is the only Australian representative for an international genus, Hildegardia. Under Northern Territory legislation, it’s listed as “near threatened”, due to its small numbers and limited distribution.

The genus Hildegardia was named in 1832 by Austrian botanists Schott and Endlicher. They named it after Hildegard, the 11th-century German abbess and mystic, the “Sybil of the Rhine”.

The genus retains some of this mystical and elusive nature. It’s rare with small isolated populations, traits that seem to dominate for all bar one of the species in the genus.

Twelve species of Hildegardia are recognised: one from Cuba, three from Africa, four from Madagascar and one each from India, the Philippines, Indonesia and Australia.

This bizarre global distribution is even more unusual in that almost the entire generic lineage seems to be verging on extinction.

The Australian species fits this pattern of small fragmented populations and, despite being a reasonably sized tree at up to 10 metres tall, remained unknown until 1991.

Rarely seen and hard to find

Generally, Hildegardia species are tall, deciduous trees of well-drained areas, often growing on rocky hills.

Their trunks have a smooth, thin bark, which smells unpleasant and exudes a gum when wounded. Most species have heart-shaped leaves and bear a profusion of orange-red flowers when leafless. These are followed by strange, winged fruits with one or two seeds.

Hildegardia australiensis would have to be one of the most rarely seen trees in Australia in its natural habitat. It is native to the margins of the western Arnhem Land Plateau with scattered populations on limestone and sandstone scree slopes.

These are all difficult locations to visit, so if you really want to see it, a helicopter is recommended. Fortunately it is easy to grow and has found its way into limited cultivation.

Several trees have been in the Darwin Botanic Gardens since the early ’90s and a few are known to have been planted in some of the urban parks in greater Darwin. The plantings have been more to showcase a rare and odd-looking tree rather than any great ornamental value.

Growing on ‘sickness country’

In the NT the tree is so poorly known that it has no common name other than the default generic name of Hildegardia.

It appears to have no recorded Indigenous uses, which is perhaps not surprising as much of its distribution is in “sickness country”.

This is country with uranium deposits and was avoided by the traditional owners. Rock art showing figures with swollen joints has been interpreted as showing radiation poisoning.

But it does have one claim to fame. A heated debate between conservationists and miners was sparked during a proposed development of the Coronation Hill gold, platinum and palladium mine in Kakadu National Park.

The main population of H. australiensis is only a stone’s throw from Coronation Hill and the species became one of the key identified biodiversity assets that could have been threatened by development of the mine.

The area around Coronation Hill, or Guratba in the local Jawoyn language, is also of considerable spiritual significance to the Jawoyn traditional landowners and forms part of the identified “sickness country”. A creation deity, Bula, rests and lays dormant under the sickness country and should not be disturbed.

Eventually, these concerns culminated in the Hawke government decision on June 17 1991 to no longer allow the mine development.




Read more:
The Price of God at Coronation Hill


So are the seeds edible?

While there appears to be no known uses of the Australian species, the tree may have hidden potential.

The closely related trees Sterculia and Brachychiton are well known as bush tucker plants and good sources of fibre. The local Top End species Sterculia quadrifida, for instance, is commonly known as the Peanut Tree and is a highly favoured bush tucker plant.

The fibre potential of H. australiensis is being explored by internationally acclaimed Darwin-based papermaker, Winsome Jobling. Cyclone Marcus whipped through Darwin in 2018 and one of the casualties was a planted tree of H. australiensis in the Darwin Botanic Gardens.

Thankfully, material was salvaged. Winsome has material stored in her freezer awaiting extraction and processing to see what the fibre potential is.

H. barteri, an African species in the Hildegardia genus, has a broad distribution through half-a-dozen African countries. And the West African locals have a number of uses for it, from eating the seeds to using the bark as fibre for ropes. But we don’t know just yet if the flesh or seed in the Australian species is edible.

Whether the Australian species might also harbour such useful properties still awaits some testing and research. Fortunately, with the creation deity Bula watching over the natural populations, the species, unlike many of its close relatives, appears secure in the wild.


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 John 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.

A detailed eucalypt family tree helps us see how they came to dominate Australia



File 20190312 86690 1fiqo8w.jpg?ixlib=rb 1.1
In Australia you can have any tree you want, as long as it’s a eucalypt.
Shutterstock

Andrew Thornhill, James Cook University

Eucalypts dominate Australia’s landscape like no other plant group in the world.

Europe’s pine forests consist of many different types of trees. North America’s forests change over the width of the continent, from redwood, to pine and oak, to deserts and grassland. Africa is a mixture of savannah, rainforest and desert. South America has rainforests that contain the most diversity of trees in one place. Antarctica has tree fossils.

But in Australia we have the eucalypts, an informal name for three plant genera: Angophora, Corymbia and Eucalyptus. They are the dominant tree in great diversity just about everywhere, except for a small region of mulga, rainforest and some deserts.

My research, published today, has sequenced the DNA of more than 700 eucalypt species to map how they came to dominate the continent. We found eucalypts have been in Australia for at least 60 million years, but a comparatively recent explosion in diversity 2 million years ago is the secret to their spread across southern Australia.

Hundreds of species

The oldest known Eucalyptus macrofossil, from Patagonia in South America, is 52 million years old. The fossil pollen record also provides evidence of eucalypts in Australia for 45 million years, with the oldest specimen coming from Bass Strait.

Despite the antiquity of the eucalypts, researchers assumed they did not begin to spread around Australia until the continent began drying up around 20 million years ago, when Australia was covered in rainforests. But once drier environmental conditions kicked in, the eucalypts seized their chance and took over, especially in southeastern Australia.

Eucalypts are classified by their various characteristics, including the number of buds.
Mary and Andrew/flickr, CC BY-NC-SA

There are over 800 described species of eucalypts. Most of them are native only to Australia, although some have managed to naturally escape further north to New Guinea, Timor and Indonesia. Many eucalypts have been introduced to other parts of the world, including California, where Aussie eucalypts make cameos in Hollywood movies.

Eucalypts can grow as tall trees, as various multi-trunk or single-trunk trees, or in rare cases as shrubs. The combination of main characteristics – such as leaf shape, fruit shape, bud number and bark type – provided botanists with enough evidence to describe 800 species and estimate how they were all related to each other, a field of science known as “taxonomy”.

Since the 1990s and early 2000s, taxonomy has been slightly superseded by a new field called “phylogenetics”. This is the study of how organisms are related to each other using DNA, which produces something akin to a family tree.

Phylogenetics still relies on the species to be named though, so there is something to sample. New scientific fields rely on the old. There have been a number of eucalypt phylogenetic studies over the years, but none have ever sampled all of the eucalypt species in one phylogeny.




Read more:
Stringybark is tough as boots (and gave us the word ‘Eucalyptus’)


Our new paper in Australian Systematic Botany aimed to change that. We attempted to genetically sample every described eucalypt species and place them in one phylogeny to determine how they are related to each other. We sampled 711 species (86% of all eucalypts) as well as rainforest species considered most closely related to the eucalypts.

We also dated the phylogeny by time-stamping certain parts using the ages of the fossils mentioned above. This allowed us to estimate how old eucalypt groups are and when they separated from each other in the past.

Not so ancient

We found that the eucalypts are an old group that date back at least 60 million years. This aligns with previous studies and the fossil record. However, a lot of the diversification in the Eucalyptus genus has happened only in the last 2 million years.

Gum trees are iconic Australian eucalypts.
Shutterstock

Hundreds of species have appeared very recently in evolutionary history. Studies on other organisms have shown rapid diversification, but none of them compare to the eucalypts. Many species of the eucalypt forests of southeastern Australia are new in evolutionary terms (10 million years or less).

This includes many of the tall eucalypts that grow in the wet forests of southern Australia. They are not, as was previously assumed, ancient remnants from Gondwana, a supercontinent that gradually broke up between 180 million and 45 million years ago and resulted in the continents of Australia, Africa, South America and Antarctica, as well as India, New Zealand, New Guinea and New Caledonia.

The eucalypts that grow natively overseas have only made it out from Australia in the last 2 million years or less. Other groups in the eucalypts such as Angophora and Corymbia didn’t exhibit the same rapid diversification as the Eucalyptus species.




Read more:
Renewable jet fuel could be growing on Australia’s iconic gum trees


What we confirmed with the fossil record using our phylogeny is that until very recently, and I mean in terms of the Earth being 4 billion years old, the vegetation of southeastern Australia was vastly different.

At some point in the last 2-10 million years the Eucalyptus arrived in new environmental conditions. They thrived, they most likely helped spread fire to wipe out their competition, and they then rapidly changed their physical form to give us the many species that we see today.

Very few other groups in the world have made this amount of change so quickly, and arguably dramatically. The east coast of Australia would look very different if it wasn’t dominated by gum trees.

The next time you’re in a eucalypt forest, take a look around and notice all of the different types of bark and gumnuts and leaves on the trees, and know that all of that diversity has happened quite recently, but with a deep and long link to trees that once grew in Gondwana.

They have been highly advantageous, highly adaptable and, with the exception of a small number of species, are uniquely Australian. They are, as the press would put it, “a great Australian success story”.The Conversation

Andrew Thornhill, Research botanist, James Cook University

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

The swamp foxtail’s origin is hidden in its DNA



File 20190405 123431 tb8724.png?ixlib=rb 1.1
Swamp foxtail is prized in ornamental gardens across Australia.
John Tann/Flickr, CC BY-SA

Roderick John Fensham, The University of Queensland

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


Swamp foxtail (Cenchrus purpurascens) is a delightful grass that forms a neat tussock up to a metre tall with a distinctive fluffy spikelet that resembles a fox’s tail.

Foxtails are widely used in horticulture. The purple forms are particularly popular in ornamental gardens and some have even become invasive weeds.

The foxtail grasses are more commonly seen in these cultivated settings, which has led to much confusion about swamp foxtails’ origins in Australia. The species is simultaneously an exotic weed from Asia, the dominant grass in an endangered Australian ecosystem and a rare native species in isolated desert springs.



The Conversation

Is it native?

It was uncertain for a while whether swamp foxtail is actually native to Australia. Although Europeans collected it near Sydney, it was possible the seeds had come with livestock on the early ships.

This theory was put to rest by genetic studies that found small populations have existed in inland Queensland for hundreds of thousands of years.

The species spread southward and was first recorded in Victoria in the 1970s.

European records

Robert Brown, the botanist who accompanied Matthew Flinders as he circumnavigated the continent, made the the earliest European collections of the swamp foxtail near Sydney in 1802.

Despite the early date of the collections, it is feasible that the swamp foxtail was brought to Sydney within 14 years of settlement as a byproduct among grain or hay. However, while the species occurs naturally in Asia, the Javanese ports were not on the typical travelling route from Europe.




Read more:
Spinifex grass would like us to stop putting out bushfires, please


The intrepid adventurer Ludwig Leichardt later collected this species near the Gwydir River region. This collection provides more convincing evidence the swamp foxtail is native to Australia. It seems unlikely that, in the early years of colonisation, the swamp foxtail had been transported overland with the squatters who were spreading out from their successful properties in the Hunter Valley.

The spread southward

The history of herbarium records, from collections in the late 1800s and early 1900s, suggests swamp foxtail might have been native to Queensland and New South Wales.

Collections south of these locations happened after 1940. The species was not recorded in Victoria until the 1970s. It seems almost certain the swamp foxtail spread southward during the 20th century, in some places as an undesirable weed.

Unusual and isolated habitats

Aboriginal fire management possibly maintained natural grassy openings among the northern NSW rainforests. The curious “grasses”, as they were named, are well documented on early survey plans of the Big Scrub country. Many a place name, Howards Grass Road and Lagoon Grass Road among them, bear testament to their existence.

An extremely isolated population of the swamp foxtail at Elizabeth Springs in western Queensland.
Rod Fensham

The surveyors provided detailed recordings of the dominant grass on the valley floors: the “foxtail”. The swamp foxtail is now rather rare on the valley floors of the Richmond and the Tweed River valleys, replaced by crops on prime agricultural land. It managed to survive in a few locations west of Murwillumbah and on springs, but large expanses of the foxtail grasslands have succumbed to the plough.

A particularly unusual habitat for the swamp foxtail is the artesian springs that feed permanent wetlands in the semi-deserts of inland Queensland. The swamp foxtail occurs there in very local populations separated by hundreds of kilometres.

This raises the question: is the swamp foxtail a recent arrival on these tiny, strange and isolated ecosystems, or are these ancient populations?

Genetic studies have provided conclusive evidence of an ancient origin. The oldest lineage is the population at Elizabeth Springs to the south of Boulia. Its molecular signature suggests this population has been isolated for hundreds of thousands of years.

Where swamp foxtail does occur at springs, it is always accompanied by rare species that are seen only in those unusual wetlands.




Read more:
Grass trees aren’t a grass (and they’re not trees)


Crossing continents and climates

Swamp foxtail demonstrates the complexity of defining a species’ origin. This species probably evolved in Asia, because this is where most of its relatives are found. It found its way to Australia, possibly through a migratory bird that dropped a seed in a desert spring.

It then had a second migration, either from the springs or from a repeat dispersal from Asia, and found a niche in the valley floors of subtropical landscapes. It was abundant in these moist and fertile habitats when Europeans colonised the continent in 1788.

Since then, the swamp foxtail has spread to temperate climates where it has become invasive and, in some situations, a minor pest. Quite a journey.The Conversation

Roderick John Fensham, Associate Professor of Biological Sciences, The University of Queensland

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