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

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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.




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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.




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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.

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



A giant guitarfish caught in West Papua is hung from a fishing boat. Guitarfish are in trouble, according to the IUCN Red List.
Conservation International/Abdy Hasan, Author provided

Peter Kyne, Charles Darwin University

More than 28,000 species around the world are threatened, according to the Red List of Threatened Species compiled by the International Union for the Conservation of Nature (IUCN). The list, updated on Thursday night, has assessed the extinction risk of almost 106,000 species and found more than a quarter are in trouble.

While recent headline-grabbing estimates put as many as 1 million species facing extinction, these were based on approximations, whereas the IUCN uses rigorous criteria to assess each species, creating the world-standard guide to biodiversity extinction risk.




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In this update, 105,732 species were ranked from least concern (little to no risk of extinction), to critically endangered (an extremely high risk of extinction) and extinct (the last individual of a species has expired).

This Red List update doesn’t hold a lot of good news. It takes the total number of threatened species to 28,338 (or 27% of those assessed) and logs the extinction of 873 species since the year 1500.

These numbers seem small when thinking about the estimated 1 million species at risk of extinction, but only around 1% of the world’s animals, fungi and plants have been formally assessed on the IUCN Red List. As more species are assessed, the number of threatened species will no doubt grow.

More than 7,000 species from around the world were added to the Red List in this update. This includes 501 Australian species, ranging from dragonflies to fish.

The shortfin eel (Anguilla australis) has been assessed as near threatened due to poor water and river management, land clearing, nutrient run-off, and recurring drought.

The Australian shortfin eel is under threat from drought and land clearing.

Twenty Australian dragonflies were also assessed for the first time, including five species with restricted ranges under threat from habitat loss and degradation. Urban and mining expansion pose serious threats to the western swiftwing (Lathrocordulia metallica), which is only found in Western Australia.

Plight of the rhino rays

I coordinate shark and ray Red List assessments for the IUCN. Of particular concern in this update is the plight of some unique and strange fishes: wedgefishes and giant guitarfishes, collectively known as “rhino rays”.

This group of shark-like rays, which range from Australia to the Eastern Atlantic, are perilously close to extinction. All six giant guitarfishes and nine out of 10 wedgefishes are critically endangered.

Bottlenose wedgefish in Raja Ampat, Indonesia.
Credit: Arnaud Brival

While rhino ray populations are faring comparatively well in Australia, this is not the case throughout their wider Indo-Pacific and, in some cases, Eastern Atlantic ranges, where they are subject to intense and often unregulated exploitation.

The predicament of rhino rays is driven by overfishing for meat and their valuable fins. Their meat is often eaten or traded locally and, along with other sharks, rays and bony fishes, is an important part of coastal livelihoods and food security in tropical countries. Their fins are traded internationally to meet demand for shark fin soup. The “white fins” of rhino rays are highly prized in the trade and can fetch close to US$1,000 per kilogram.




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This exploitation for a high-value yet small body part places the rhino rays in the company of the rhinoceroses in more than name alone.

Bottlenose wedgefish in the Kota Kinabalu fish market in Malaysia.
Peter Kyne

Two species in particular may be very close to extinction. The clown wedgefish (Rhynchobatus cooki) from the Indo-Malay Archipelago has been seen only once in over 20 years – when a local researcher photographed a dead specimen in a Singapore fish market.

The false shark ray (Rhynchorhina mauritaniensis) is known from only one location in Mauritania in West Africa, and there have been no recent sightings. It’s likely increased fishing has taken a serious toll; the number of small fishing boats in Mauritania has risen from 125 in 1950 to nearly 4,000 in 2005.

This rising level of fishing effort is mirrored in the tropical nations of the Indo-West Pacific where most rhino rays are found.

Effective rhino ray conservation will require a suite of measures working in concert: national species protection, habitat management, bycatch reduction and international trade restrictions. These are not quick and easy solutions; all will be dependent on effective enforcement and compliance.




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From sharks in seagrass to manatees in mangroves, we’ve found large marine species in some surprising places


The challenges of saving rhino rays illustrate the larger, mammoth task of tackling our current extinction crisis. But the cost of inaction is even larger: precipitous loss of biodiversity and, eventually, the collapse of the ecosystems on which we depend.


This article was co-written by Caroline Pollock, Program Officer for the IUCN’s Red List Unit.The Conversation

Peter Kyne, Senior Research Fellow in conservation biology, Charles Darwin University

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