Deadly frog fungus has wiped out 90 species and threatens hundreds more



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The Mossy Red-eyed Frog is among hundreds of species threatened with extinction at the hands of chytrid fungus.
Jonathan Kolby/Honduras Amphibian Rescue and Conservation Center

Benjamin Scheele, Australian National University and Claire Foster, Australian National University

It started off as an enigma. Biologists at field sites around the world reported that frogs had simply disappeared. Costa Rica, 1987: the golden toad, missing. Australia, 1979: the gastric brooding frog, gone. In Ecuador, Arthur’s stubfoot toad was last seen in 1988.

By 1990, cases of unexplained frog declines were piling up. These were not isolated incidents; it was a global pattern – one that we now know was due to chytridiomycosis, a fungal disease that was infecting and killing a huge range of frogs, toads and salamanders.

Our research, published today in Science, reveals the global number of amphibian species affected. At least 501 species have declined due to chytrid, and 90 of them are confirmed or believed extinct.




Read more:
Where did the frog pandemic come from?


When biologists first began to investigate the mysterious species disappearances, they were at a loss to explain them. In many cases, species declined rapidly in seemingly pristine habitat.

Species declines typically have obvious causes, such as habitat loss or introduced species like rats. But this was different.

The first big breakthrough came in 1998, when a team of Australian and international scientists led by Lee Berger discovered amphibian chytrid fungus. Their research showed that this unusual fungal pathogen was the cause of frog declines in the rainforests of Australia and Central America.

However, there were still many unknowns. Where did this pathogen come from? How does it kill frogs? And why were so many different species affected?

After years of painstaking research, biologists have filled in many pieces of the puzzle. In 2009, researchers discovered how chytrid fungus kills frogs. In 2018, the Korean peninsula was pinpointed as the likely origin of the most deadly lineage of chytrid fungus, and human dispersal of amphibians suggested as a likely source of the global spread of the pathogen.

Yet as the mystery was slowly but surely unravelled, a key question remained: how many amphibian species have been affected by chytrid fungus?

Early estimates suggested that about 200 species were affected. Our new study reveals the total is unfortunately much larger: 501 species have declined, and 90 confirmed or suspected to have been killed off altogether.

The toll taken by chytrid fungus on amphibians around the world. Each bar represents one species; colours reveal the extent of population declines.
Scheele et al. Science 2019

Devastating killer

These numbers put chytrid fungus in the worst league of invasive species worldwide, threatening similar numbers of species as rats and cats. The worst-hit areas have been in Australia and Central and South America, which have many different frog species, as well as ideal conditions for the growth of chytrid fungus.

Large species and those with small distributions and elevational ranges have been the mostly likely to experience severe declines or extinctions.

Together with 41 amphibian experts from around the world, we pieced together information on the timing of species declines using published records, survey data, and museum collections. We found that declines peaked globally in the 1980s, about 15 years before the disease was even discovered. This peak coincides with biologists’ anecdotal reports of unusual amphibian declines that occurred with increasing frequency in the late 1980s.

Encouragingly, some species have shown signs of natural recovery. Twelve per cent of the 501 species have begun to recover in some locations. But for the vast majority of species, population numbers are still far below what they once were.

Most of the afflicted species have not yet begun to bounce back, and many continue to decline. Rapid and substantial action from governments and conservation organisations is needed if we are to keep these species off the extinct list.




Read more:
Saving amphibians from a deadly fungus means acting without knowing all the answers


In Australia, chytrid fungus has caused the decline of 43 frog species. Of these, seven are now extinct and six are at high risk of extinction due to severe and ongoing declines. The conservation of these species is dependent on targeted management, such as the recovery program for the iconic corroboree frogs.

The southern corroboree frog: hopefully not a disappearing icon.
Corey Doughty

Importantly, there are still some areas of the world that chytrid has not yet reached, such as New Guinea. Stopping chytrid fungus spreading to these areas will require a dramatic reduction in the global trade of amphibians, as well as increased biosecurity measures.

The unprecedented deadliness of a single disease affecting an entire class of animals highlights the need for governments and international organisations to take the threat of wildlife disease seriously. Losing more amazing species like the golden toad and gastric brooding frog is a tragedy that we can avoid.The Conversation

Benjamin Scheele, Research Fellow in Ecology, Australian National University and Claire Foster, Research Fellow in Ecology and Conservation, Australian National University

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

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Why extinct species seem to be returning from the dead



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The first Fernandina giant tortoise seen in over 112 years.
Galapagos National Park Directorate

David Roberts, University of Kent

Like something out of a zombie movie, species that were once thought extinct seem to be rising from the dead. Between February 21 and March 4 2019, three notable rediscoveries were announced – the Fernandina Island Galápagos tortoise (Chelonoidis phantasticus), which was last seen in 1906; Wallace’s giant bee (Megachile pluto), which had supposedly disappeared in 1980; and the Formosan clouded leopard (Neofelis nebulosa brachyura), which disappeared after the last sighting in 1983 and was officially declared extinct in 2013.

These rediscoveries suggest we may know very little about some of the world’s rarest species, but they also raise the question of how species are declared extinct in the first place. The IUCN Red List collates a global register of threatened species and measures their relative risks of extinction. The Red List has a set of criteria to determine the threat status of a species, which are only listed as “Extinct” when…

… there is no reasonable doubt that the last individual has died.

According to the Red List, this requires…

… exhaustive surveys in known and/or expected habitat, at appropriate times… throughout its historic range [which] have failed to record an individual. Surveys should be over a time frame appropriate to the taxon’s life cycle and life form.

Given all the evidence – or rather, lack of evidence – that’s needed, it’s surprising that any species is ever declared extinct. The criteria show that to understand whether a species is extinct, we need to know what it was doing in the past.

The world’s largest bee was presumed extinct before rediscovery in Indonesia in February 2019.
Stavenn/Wikipedia, CC BY-SA

Sightings at a certain time and in a certain place make up our knowledge of a species’ survival, but when a species becomes rare, sightings are increasingly infrequent so that people start to wonder whether the species still exists.

People often use the time since the last sighting as a measure of likelihood when deciding if a species has died out, but the last sighting is rarely the last individual of the species or the actual date of extinction.

Instead, the species may persist for years without being seen, but the length of time since the last sighting strongly influences assumptions as to whether a species has gone extinct or not.

But what is a sighting? It can come in a variety of forms, from direct observation of a live individual in the flesh or in photographs, indirect evidence such as foot prints, scratches and faeces, and oral accounts from interviews with eyewitnesses.

The Formosan clouded leopard is endemic to Taiwan and considered extinct, but eyewitness accounts keep speculation alive.
Joseph Wolf/Wikipedia

But these different lines of evidence aren’t all worth the same – a bird in the hand is worth more than a roomful of recollections from people who saw it in the past. Trying to determine what are true sightings and what are false complicates the declaration of extinction.

The idea of a species being “rediscovered” can confuse things further. Rediscovery implies that something was lost or forgotten but the term often gives the impression that a species has returned from the dead – hence the term “lazarus species”. This misinterpretation of lost or forgotten species means the default assumption is extinction for any species that hasn’t been seen for a number of years.

So, what does this mean for the three recently “rediscovered” species?

While a living specimen of the Fernandina Island Galápagos tortoise had not been seen since 1906, indirect observations of tortoise faeces, footprints and tortoise-like bite marks out of prickly pear cacti had been made as recently as 2013.

The uncertainty around the quality of these later observations and the long time since the last living sighting probably contributed to it being declared “Critically Endangered (Possibly Extinct)” in 2015. In the natural world, a species is presumed extinct until proven living.

Thought to be the last of its kind, this Fernandina Island Galápagos tortoise specimen was collected in 1906.
John Van Denburgh/Wikipedia

Wallace’s giant bee may not have been recorded in the last 38 years but it was never actually declared extinct according to the IUCN Red List. In fact, for many years it languished under the criteria of Data Deficient and was only recently assessed as Vulnerable.

So, while this is an exciting find for something that hadn’t been seen for so long, its rediscovery shows how little is known about many rare species in the wild, rather than how scarce they are.

The Formosan clouded leopard, meanwhile, was actually listed as Extinct. The last sighting of the species was in 1983, based on interviews with 70 hunters, and extensive camera trapping during the 2000s failed to detect its presence. It was officially declared extinct in 2013.

While the giant tortoise and bee were proclaimed alive after living specimens were found, the clouded leopard’s rediscovery is more uncertain. Based on sightings on two separate occasions by two sets of wildlife rangers, the evidence is compelling. But whether the Formosan Clouded Leopard has really risen from the dead will require considerably more effort to prove.The Conversation

David Roberts, Reader in Biodiversity Conservation, University of Kent

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

An end to endings: how to stop more Australian species going extinct



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John Gerrard Keulemans. Published by Muséum national d’histoire naturelle (France)

John Woinarski, Charles Darwin University; Sarah Legge, Australian National University, and Stephen Garnett, Charles Darwin University

This is part of a major series called Advancing Australia, in which leading academics examine the key issues facing Australia in the lead-up to the 2019 federal election and beyond. Read the other pieces in the series here.


We need nature. It gives us inspiration, health, resources, life. But we are losing it. Extinction is the most acute and irreversible manifestation of this loss.

Australian species have suffered at a disproportionate rate. Far more mammal species have become extinct in Australia than in any other country over the past 200 years.

The thylacine is the most recognised and mourned of our lost species, but the lesser bilby has gone, so too the pig-footed bandicoot, the Toolache wallaby, the white-footed rabbit-rat, along with many other mammals that lived only in Australia. The paradise parrot has joined them, the robust white-eye, the King Island emu, the Christmas Island forest skink, the southern gastric-brooding frog, the Phillip Island glory pea, and at least another 100 species that were part of the fabric of this land, part of what made Australia distinctive.

And that’s just the tally for known extinctions. Many more have been lost without ever being named. Still others hover in the graveyard – we’re not sure whether they linger or are gone.




Read more:
What makes some species more likely to go extinct?


The losses continue: three Australian vertebrate species became extinct in the past decade. Most of the factors that caused the losses remain unchecked, and new threats are appearing, intensifying, expanding. Many species persist only in slivers of their former range and in a fraction of their previous abundance, and the long-established momentum of their decline will soon take them over the brink.

The toolache wallaby is just one of Australia’s many extinct species.
John Gould, F.R.S., Mammals of Australia, Vol. II Plate 19, London, 1863

Unnecessarily extinct

These losses need not have happened. Almost all were predictable and preventable. They represent failures in our duty of care, legislation, policy and management. They give witness to, and warn us about, the malaise of our land and waters.

How do we staunch the wound and maintain Australia’s wildlife? It’s a problem with many facets and no single solution. Here we provide ten recommendations, based on an underlying recognition that more extinctions will be inevitable unless we treat nature as part of the essence of this country, rather than as a dispensable tangent, an economic externality.

  1. We should commit to preventing any more extinctions. As a society, we need to treat our nature with more respect – our plants and animals have lived in this place for hundreds of thousands, often millions, of years. They are integral to this country. We should not deny them their existence.

  2. We should craft an intergenerational social contract. We have been gifted an extraordinary nature. We have an obligation to pass to following generations a world as full of wonder, beauty and diversity as our generation has inherited.

  3. We should highlight our respect for, and obligation to, nature in our constitution, just as that fusty document could be refreshed and some of its deficiencies redressed through the Uluru Statement from the Heart. Those drafting the blueprint for the way our country is governed gave little or no heed to its nature. A constitution is more than a simple administrative rule book. Countries such as Ecuador, Palau and Bhutan have constitutions that commit to caring for their natural legacy and recognise that society and nature are interdependent.

  4. We should build a generation-scale funding commitment and long-term vision to escape the fickle, futile, three-year cycle of contested government funding. Environmental challenges in Australia are deeply ingrained and longstanding, and the conservation response and its resourcing need to be implemented on a scale of decades.

  5. As Paul Keating stated in his landmark Redfern speech, we should all see Australia through Aboriginal eyes – more deeply feel the way the country’s heart beats; become part of the land; fit into the landscape. This can happen through teaching curricula, through reverting to Indigenous names for landmarks, through reinvigorating Indigenous land management, and through pervasive cultural respect.

  6. We need to live within our environmental limits – constraining the use of water, soil and other natural resources to levels that are sustainable, restraining population growth and setting a positive example to the world in our efforts to minimise climate change.

  7. We need to celebrate and learn from our successes. There are now many examples of how good management and investments can help threatened species recover. We are capable of reversing our mismanagement.

  8. Funding to prevent extinctions is woefully inadequate, of course, and needs to be increased. The budgeting is opaque, but the Australian government spends about A$200 million a year on the conservation of threatened species, about 10% of what the US government outlays for its own threatened species. Understandably, our American counterparts are more successful. For context, Australians spend about A$4 billion a year caring for pet cats.

  9. Environmental law needs strengthening. Too much is discretionary and enforcement is patchy. We suggest tightening the accountability for environmental failures, including extinction. Should species die out, formal inquests should be mandatory to learn the necessary lessons and make systemic improvements.

  10. We need to enhance our environmental research, management and monitoring capability. Many threatened species remain poorly known and most are not adequately monitored. This makes it is hard to measure progress in response to management, or the speed of their collapse towards extinction.




Read more:
Eulogy for a seastar, Australia’s first recorded marine extinction


Extinction is not inevitable. It is a failure, potentially even a crime – a theft from the future that is entirely preventable. We can and should prevent extinctions, and safeguard and celebrate the diversity of Australian life.The Conversation

John Woinarski, Professor (conservation biology), Charles Darwin University; Sarah Legge, Professor, Australian National University, and Stephen Garnett, Professor of Conservation and Sustainable Livelihoods, Charles Darwin University

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

It’s fish on ice, as frozen zoos make a last-ditch attempt to prevent extinction


Nicola Marie Rivers, Monash University

Twenty-six of the forty-six fish species known to live in the Murray-Darling basin are listed as rare or threatened. Recent fish kills in the iconic river system are a grim reminder of how quickly things can take a turn for the worst.

A sudden drop in population size can push a species towards extinction, but there may be hope for resurrection. Frozen zoos store genetic material from endangered species and are preparing to make new individuals if an extinction occurs.




Read more:
Cryopreservation: the field of possibilities


Unfortunately, poor response to freezing has hindered the introduction of fish into frozen zoos in the past. Now new techniques may provide them safe passage.

Ice ice baby

A frozen zoo, also known as a biobank or cryobank, stores cryopreserved or “frozen” cells from endangered species. The primary purpose of a frozen zoo is to provide a backup of endangered life on Earth allowing us to restore extinct species.

Reproductive cells, such as sperm, oocytes (eggs) and embryos, are cooled to -196ºC, at which point all cellular function is paused. When a sample is needed, the cells are warmed and used in breeding programs to produce new individuals, or to study their DNA to determine genetic relationships with other species.

There are several cryobanking facilities in Australia, including the Australian Frozen Zoo (where I work), the CryoDiversity Bank and the Ian Potter Australian Wildlife Biobank, as well as private collections. These cryobanks safeguard some of Australia’s most unique wildlife including the greater bilby, the golden bandicoot, and the yellow-footed rock wallaby as well as other exotic species such as the black rhino and orangutans.

Internationally, frozen zoos are working together to build a “Noah’s Ark” of frozen tissue. The Frozen Ark project, established in 2004 at the University of Nottingham, now consists of over 5,000 species housed in 22 facilities across the globe.

The Manchurian trout, or lenok, is the only fish successfully reproduced through cryopreservation and surrogacy.
National Institute of Ecology via Wikimedia, CC BY

Less love for fish

As more and more species move into frozen zoos, fish are at risk of being left out. Despite years of research, no long-term survival has been reported in fish eggs or embryos after cryopreservation. However, precursors of sperm and eggs known as gonial cells found in the developing embryo or the ovary or testis of adult fish have been preserved successfully in several species including brown trout, rainbow trout, tench and goby.

By freezing these precursory cells, we now have a viable method of storing fish genetics but, unlike eggs and sperm, the cells are not mature and cannot be used to produce offspring in this form.

To transform the cells into sperm and eggs, they are transplanted into a surrogate fish. Donor cells are injected into the surrogate where they follow instructions from surrounding cells which tell them where to go and when and how to make sperm or eggs.

Once the surrogate is sexually mature they can mate and produce offspring that are direct decedents of the endangered species the donor cells were originally collected from. In a way, we are hijacking the reproductive biology of the surrogate species. By selecting surrogates that are prolific breeders we can essentially “mass produce” sperm and eggs from an endangered species, potentially producing more offspring than it would have been able to within its own lifetime.

Cell surrogacy has been successful in sturgeon, rainbow trout and zebrafish.

The combination of cryopreservation and surrogacy in conservation is promising but has only successfully been used in one endangered species so far, the Manchurian trout.

Not a get-out-of-conservation card

The “store now, save later” strategy of frozen zoos sounds simple but alas it is not. The methods needed to reproduce many species from frozen tissue are still being developed and may take years to perfect. The cost of maintaining frozen collections and developing methods of resurrection could divert funding from preventative conservation efforts.

Even if de-extinction is possible, there could be problems. The Australian landscape is evolving – temperatures fluctuate, habitats change, new predators and diseases are being introduced. Extinction is a consequence of failing to adapt to these changes. Reintroducing a species into the same hostile environment that lead to its demise may be a fool’s errand. How can we ensure reintroduced animals will thrive in an environment they may no longer be suited for?

Reducing human impact on the natural environment and actively protecting threatened species will be far easier than trying to resurrect them once they are gone. In the case of the Murray Darling Basin, reversing the damage done and developing policies that ensure its long-term protection will take time that endangered species may not have.




Read more:
I’ve always wondered: does anyone my age have any chance of living for centuries?


Frozen zoos are an insurance policy, and we don’t want to have to use them. But if we fail in our fight against extinction, we will be glad we made the investment in frozen zoos when we had the chance.The Conversation

Nicola Marie Rivers, PhD Candidate, Monash University

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

Eulogy for a seastar, Australia’s first recorded marine extinction



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The Derwent River Sea Star was only documented for 25 years before its extinction.
Blair Patulo, Museums Victoria, CC BY-NC

Tim O’Hara, Museums Victoria

We see the surface of the sea: the rock pools, the waves, the horizon. But there is so much more going on underneath, hidden from view.

The sea’s surface conceals human impact as well. Today, I am writing a eulogy to the Derwent River Seastar (or starfish), that formerly inhabited the shores near the Tasman Bridge in Hobart, Tasmania. It is Australia’s first documented marine animal extinction and one of the few recorded anywhere in the world.




Read more:
Extinction is a natural process, but it’s happening at 1,000 times the normal speed


https://giphy.com/embed/TgFkyRxbZCTLx8OEqF

The Derwent River Seastar, preserved in the Tasmanian Museum and Art Gallery, Hobart. Credit: Christy Hipsley, Museums Victoria/University of Melbourne

Scientists only knew the Derwent River Seastar for about 25 years. It was first described in 1969 by Alan Dartnall, a former curator of the Tasmanian Museum and Art Gallery. It was found on and off until the early 1990s but scientists noted a decline in numbers. Targeted surveys in 1993 and 2010 failed to find a single individual.

It was listed as critically endangered by the Tasmanian and Australian governments. But now, like a long-lost missing person, it is time to call it: the Derwent River Seastar appears extinct.

It is actually quite hard to document the extinction of marine animals. There is always hope that it will turn up in some unusual spot, somewhere in that hidden world. Australia has an ambitious plan to create high-resolution maps of 50% of our marine environment by 2025. This is a formidable task. But it is a reflection of our lack of knowledge about the oceans that, 20 years after the launch of Google Maps and despite an enormous effort in the interim, much of Australia’s seafloor in 2025 will be still largely known from the occasional 19th-century depth sounding, or imprecise gravity measurements from satellites.

We do notice when big animals go. There used to be a gigantic dugong-like creature called Steller’s Sea Cow, which lived in the North Pacific Ocean until it was hunted to oblivion by 1768. There is no mistaking that loss.

Steller’s Sea Cow, which grew up to 10 metres long and weighed between five and ten tonnes, was hunted to extinction in 1768.
Paul K/Flickr, CC BY

But the vast majority of the estimated 1 million to 2 million marine animals are invertebrates, animals without backbones such as shells, crabs, corals and seastars. We just don’t monitor those enough to observe their decline.

We noticed the Derwent River Seastar because it was only found at a few sites near a major city. Its story is intertwined with the usual developments that happen near many large ports. The Derwent River became silty and was at times heavily polluted by industrial and residential waste. The construction of the Tasman Bridge in the early 1960s cannot have helped.

From the 1920s a series of marine pests were accidentally introduced by live oysters imported from New Zealand, or by hitching a ride on ships. Some of these pests are now abundant in southeast Tasmanian waters and eat or compete with local species.




Read more:
Australia relies on volunteers to monitor its endangered species


The Derwent River Seastar has been a bit of an enigma. From the start, it was mistakenly classified as belonging to group of seastars (poranids) otherwise known from deep or polar habitats. Some people wondered whether it was an introduced species as well, one that couldn’t cope with the Derwent environment.

However, we used a CT scanner at the School of Earth Sciences, University of Melbourne, to look at the internal skeleton of one of the few museum specimens. Sure enough, it has internal struts to strengthen the body, which are characteristic of a different group of seastars (asterinids) that have adapted to coastal environments and are sometimes restricted to very small areas.

https://giphy.com/embed/3ksOMV7xcoVKhOXVE2

CT scan showing the internal structure of the seastar. Source: Christy Hipsley, Museums Victoria/University of Melbourne

Is this seastar like a canary in a coal mine, a warning of a wave of marine extinctions? Sea levels are rising with global warming, and that is going to be a big problem for life adapted to living along the shoreline. Mangroves, salt marsh, seagrass beds, mud flats, beaches and rock platforms only form at specific water depths. They are going to need to follow rising sea levels and reform higher up the shoreline.

Coastal life can take hundreds to thousands of years to adjust to these sorts of changes. But in many places we don’t have a natural environment anymore. Humans will increasingly protect coastal property by building seawalls and other infrastructure, especially around towns and bays. This will mean far less space for marine animals and plants.




Read more:
Rising seas will displace millions of people – and Australia must be ready


We need to start planning new places for our shore life to go – areas they can migrate to with rising sea levels. Otherwise, the Derwent River Seastar won’t be the last human-induced extinction from these environments.The Conversation

Tim O’Hara, Senior Curator of Marine Invertebrates, Museums Victoria

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

Tasmanian tigers were going extinct before we pushed them over the edge



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Gone since 1936, and ailing since long before that.
Tasmanian Museum and Art Gallery, Author provided

Andrew Pask, University of Melbourne

There’s no doubt that humans killed off the Tasmanian tiger. But a new genetic analysis suggests this species had been on the decline for millennia before humans arrived to drive them to extinction.

The Tasmanian tiger, also known as the thylacine, was unique. It was the largest marsupial predator that survived into recent times. Sadly it was hunted to extinction in the wild, and the last known Tasmanian tiger died in captivity in 1936.

In a paper published in Nature Ecology and Evolution today, my colleagues and I piece together its entire genetic sequence for the first time. It tells us that thylacines’ genetic health had been declining for many millennia before they first encountered human hunters.


Read more: Will we hunt dingoes to the brink like the Tasmanian tiger?


Hounded by hunters.
Tasmanian Museum and Art Gallery, Author provided

Our research also offered the chance to study the origins of the similarity in body shape between the thylacine and dogs. The two are almost identical, despite having last shared a common ancestor more than 160 million years ago – a remarkable example of so-called “convergent evolution”.

Decoding the thylacine genome allowed us to ask the question: if two animals develop an identical body shape, do they also show identical changes in their DNA?

Thylacine secrets

These questions were previously difficult to answer. The age and storage conditions of existing specimens meant that most thylacine specimens have DNA that is highly fragmented into very short segments, which are not suitable for piecing together the entire genome.

We identified a 109-year-old specimen of a young pouch thylacine in the Museums Victoria collection, which had much more intact DNA than other specimens. This gave us enough pieces to put together the entire jigsaw of its genetic makeup.

The preserved young, thylacine with enough DNA to reveal its whole genome.
Museums Victoria, Author provided

Next, we made a detailed comparison of thylacines and dogs to see just how similar they really are. We used digital imaging to compare the thylacine’s skull shape to many other mammals, and found that the thylacine was indeed very similar to various types of dog (especially the wolf and red fox), and quite different from its closest living marsupial relatives such as the numbat, Tasmanian devil, and kangaroos.

Our results confirmed that thylacines and dogs really are the best example of convergent evolution between two distantly related mammal species ever described.

We next asked whether this similarity in body form is reflected by similarity in the genes. To do this, we compared the DNA sequences of thylacine genes with those of dogs and other animals too.

While we found many similarities between thylacines’ and dogs’ genes, they were not significantly more similar than the same genes from other animals with different body shapes, such as Tasmanian devils and cows.

We therefore concluded that whatever the reason why thylacines and dogs’ skulls are so similarly shaped, it is not because evolution is driving their gene sequences to be the same.

Family ties

The thylacine genome also allowed us to deduce its precise position in the marsupial family tree, which has been a controversial topic.

Our analyses showed that the thylacine was at the root of a group called the Dasyuromorphia, which also includes the numbat and Tasmanian devil.

By examining the amount of diversity present in the single thylacine genome, we were able to estimate its effective population size during past millennia. This demographic analysis revealed extremely low genetic diversity, suggesting that if we hadn’t hunted them into extinction the population would be in very poor genetic health, just like today’s Tasmanian devils.

The less diversity you have in your genome, the more susceptible you are to disease, which might be why devils have contracted the facial tumour virus, and certainly why it has been so easily spread. The thylacine would have been at a similar risk of contracting devastating diseases.

The last thylacine alive.
Tasmanian Museum and Art Gallery, Author provided

This loss in population diversity was previously thought to have occurred as a population of thylacines (and devils) became isolated on Tasmania some 15,000 years ago, when the land bridge closed between it and the mainland.

But our analysis suggests that the process actually began much earlier – between 70,000 and 120,000 years ago. This suggests that both the devil and thylacine populations already had very poor genetic health long before the land bridge closed.


Read more: How curiosity can save species from extinction


The ConversationNow that we know the whole genome of the Tasmanian tiger, we know much more about this extinct animal and the unique place it held in Australia’s marsupial family tree. We are expanding our analyses of the genome to determine how it came to look so similar to the dog, and to continue to learn more about the genetics of this unique marsupial apex predator.

Andrew Pask, Associate Professor, University of Melbourne

This article was originally published on The Conversation. Read the original article.