The swamp foxtail’s origin is hidden in its DNA

Swamp foxtail is prized in ornamental gardens across Australia.
John Tann/Flickr, CC BY-SA

Roderick John Fensham, The University of Queensland

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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.

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The Conversation

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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.

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

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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.

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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.

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.

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

Bill Hails/The Conversarion

Kristian Bell, Deakin University

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Spinifex grass: it’s spiky, dominates a quarter of the continent, and has no recognised grazing value. To top it all off, people have reportedly experienced anaphylactic shock from being pricked by its sharp leaf tips.

Given this less-than-stellar rap sheet, you may wonder why this plant is the subject of my research attention.

Well, it turns out that these less desirable traits are also its virtue. A plethora of birds, mammals and reptiles rely on the unique plant for their survival – to such an extent that it’s considered a keystone of its environment.

For animals small enough to navigate its sharp spines, spinifex offers a fortress of safety. Everything from mallee emu wrens, to hopping mice, to the near-mythical night parrot hide out from predators in spinifex (and snack on tasty termites and ants within).

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For me, as an immigrant from the grey and drizzly lands of the UK, the bone-dry arid outback of Australia – where even the grass can harm you – was the perfect antidote to the dull, predictable safety of home.

This weird-looking plant, which always seemed to be associated with huge numbers of equally exotic animals, was so intoxicatingly new to me that I fell in love instantly. This lead to my current research: trying to stop the decline of spinifex.

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The Conversation, CC BY

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Spinifex isn’t really spinifex

To back up a little, the common name “spinifex” is a bit misleading. There’s a genus called Spinifex (mostly made up of coastal grasses), but spinifex grass doesn’t belong to it. Spinifex grass is actually part of the genus Triodia.

There are two main kinds of spinifex: an older, harder form suited to arid environments which generally grows in the south of Australia; and a “soft” form, which tends to perform better in more tropical, northerly regions.

Regardless of species, spinifex is well adapted to thrive in some of the harshest environments in Australia, growing in well-drained, infertile, sandy soils. It can cope with extremes of long-term drought and responds well to fire.

Spinifex emerging after a fire.
Author provided

You might think, given the near-ubiquity of spinifex across the arid wildernesses of Australia, and its ability to withstand poor soils, infrequent rain, extreme temperatures and fire, that this hardy plant is free from the almost inevitable stories of doom and gloom associated with many native species.

However, all is not well for some spinifex communities. Spinifex in mallee woodland, such as can be found in south-central New South Wales, has suffered from heavy clearing (mostly for agriculture), with only about 3% remaining from pre-European settlement levels.

Counterintuitively, firefighting efforts in these areas may have also hurt spinifex. Bushfires clear the land and help new spinifex plants grow; in their absence, old and decaying plants dominate. This means the habitat degrades, which could spell disaster for the many animals that rely on abundant, healthy spinifex.

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Aboriginal fire management – part of the solution to destructive bushfires

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Spinifex is such an important species that its disappearance could even precipitate an extinction cascade. Indeed, studies suggest that some reptiles rely on spinifex habitat to survive in remnant bush in farming landscapes.

Despite these issues, there is plenty to be hopeful about. Spinifex has recently attracted more attention from industry as an abundant and under-used resource, building on what many Indigenous people have known for centuries. Spinifex has traditionally been used by some Indigenous people to craft waterproof thatching for shelters, or as a source of adhesive resin.

Spinifex covers vast swathes of Australia.
Thomas Jundt/Flickr, CC BY-NC

Recent technological advances may make the plant’s nanocellulose easier to extract. That means spinifex could be a component of everything from cardboard to carbon fibre, fire hose liner, cattle tags, and even condoms.

Researchers in the field – like me – are also starting to gain a better understanding of the factors that affect spinifex. We’re creating maps of grass distribution, and reintroducing fire to areas with significant amounts of spinifex.

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Returning from time in the field with hands covered in more spinifex splinters than I can count has done nothing to dampen my ardour for this overlooked group of grasses. After all, what’s not to love about a unique plant found nowhere else in the world, that provides a refuge for some of Australia’s most iconic animals, and may also lead to safer sex in the future? No matter how many times it pricks me, I’m still coming back for more.

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

Kristian Bell, PhD candidate, Deakin University

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

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

Xanthorrhoea have no real trunk – just tightly packed leaves.
CC BY-SA

John Patykowski, Deakin University

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Grass trees (genus Xanthorrhoea) look like they were imagined by Dr Seuss. An unmistakable tuft of wiry, grass-like leaves atop a blackened, fire-charred trunk. Of all the wonderfully unique plants in Australia, surely grass trees rank among the most iconic.

The common name grass tree is a misnomer: Xanthorrhoea are not grasses, nor are they trees. Actually, they are distantly related to lilies. Xanthorrhoea translates to “yellow flow”, the genus named in reference to the ample resin produced at the bases of their leaves.

All 28 species of grass tree are native only to Australia. Xanthorrhoea started diversifying around 24-35 million years ago – shortly after the Eocene/Oligocene mass extinctions – so they have had quite some time to adapt to Australian conditions.

Wander through remnant heathland or dry sclerophyll forest, particularly throughout the eastern and south-western regions of Australia, and you’ll likely find a grass tree.

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Perfectly adapted to their environment

Xanthorrhoea are perfectly adapted to the Australian environment, and in turn, the environment has adapted to Xanthorrhoea. Let’s start the story from when a grass tree begins as a seed.

After germination, Xanthorrhoea seedlings develop roots that pull the growing tip of the plant up to 12cm below the soil surface, protecting the young plant from damage. These roots quickly bond with fungi that help supply water and minerals.

Once the tip of the young plant emerges above ground, it is protected from damage by moist, tightly packed leaf bases, although shoots may develop if it is damaged. The leaves of Xanthorrhoea are tough, but they lack prickles or spines to deter passing herbivores. Instead, they produce toxic chemicals with anaesthetising effects.

All Xanthorrhoea are perennial; some species are estimated to live for over 600 years. Most grow slowly (0.8–6 cm in height per year), but increase their rate of growth in response to season and rainfall. The most “tree-like” species grow “trunks” up to 6 metres tall, while trunkless species grow from subterranean stems.
Grass trees don’t shed their old leaves. The bases of their leaves are packed tightly around their stem, and are held together by a strong, water-proof resin.
As the old leaves accumulate, they form a thick bushy “skirt” around the trunk. This skirt is excellent habitat for native mammals. It’s also highly flammable. However, in a bushfire, the tightly-packed leaf bases shield the stem from heat, and allow grass trees to survive the passage of fire.

Fire burns the outside leaves but the centre survives.
John Patykowski, Author provided

Xanthorrhoea can recover quickly after a fire thanks to reserves of starch stored in their stem. By examining the size of a grass tree’s skirt, we can estimate when a fire last occurred.

It can take over 20 years before a grass tree produces its first flowers. When they do flower it can be spectacular, producing a spike and scape up to four metres long advertising hundreds of nectar-rich, creamy-white flowers to all manner of fauna. Flowering is not dependent on fire, but it stimulates the process. The ability of grass trees to resprout after fire and quickly produce flowers makes them a vital life-line for fauna living in recently-burnt landscapes.

Grass trees provide food for birds, insects, and mammals, which feast on the nectar, pollen, and seeds. Beetle larvae living within the flower spikes are a delicacy for cockatoos. Invertebrates such as green carpenter bees build nests inside the hollowed out scapes of flowers. Small native mammals become more abundant where grass trees are found, for the dense, unburnt skirt of leaves around the trunk provides shelter and sites for nesting.

Indigenous use of grass trees

For Indigenous people living where grass trees grow, they were (and remain) a resource of great importance.

The resin secreted by the leaf-bases was used as an adhesive to attach tool heads to handles and could be used as a sealant for water containers. This valuable and versatile resin was an important item of trade.

The base of the flowering stem was used as the base of composite spear shafts, and when dried was used to generate fire by hand-drill friction. The flowers themselves could be soaked in water to dissolve the nectar, making a sweet drink that could be fermented to create a lightly alcoholic beverage.

When young, the leaves of subspecies Xanthorrhoea australis arise from an underground stem which is seasonally surrounded by sweet, succulent roots that can be eaten. The soft leaf bases also were eaten, and the seeds were collected and ground into flour. Edible insect larvae residing at the base of grass tree stems could be collected. Honey could be collected from flower stems containing the hives of carpenter bees.

European exploitation

European settlers were quick to clue onto the usefulness of the resin , using it in the production of medicines, as a glue and varnish, and burning it as incense in churches. It was even used as a coating on metal surfaces and telephone poles, and used in the production of wine, soap, perfume and gramophone records.

The versatile resin had been used in everything from medicine to gramophones.
John Patykowski, Author provided

Resin can easily be collected from around the trunk of plants, but early settlers used more destructive methods, removing whole plants on an industrial scale. The resin was exported worldwide; during 1928-29, exported resin was valued at over £25,000 (equivalent to A$2 million today!).

We still have much to learn about grass trees. Current research indicates an extract from one subspecies can be used as a cheap, environmentally-friendly agent to synthesise silver nanoparticles that are useful for their antibacterial properties.

Threats to grass trees

Many of the oldest grass trees have been lost to land clearing, illegal collection, and changes to fire regimes. It’s vital we care for those remaining. Grass trees are particularly sensitive to Phytophthora cinnamomi, a widespread plant pathogen that is difficult to detect and control, and kills plants by restricting movement of water and nutrients through the vascular tissue.

Growing native plants can be a wonderful way to contribute to the conservation of genetic diversity, and attract native fauna into your garden. Grass trees certainly make an interesting conversation plant!

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They can easily be grown at home, provided they’re sourced from a reputable supplier. The best way is to grow from seed, but patience is required as growth can be slow. Despite being relatively hardy, grass trees do not like being moved once large or established, so translocation of plants is not advised. In my opinion, the best way to see grass trees in their true splendour is to visit them in their natural habitat.

John Patykowski, Plant ecologist, Deakin University

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