Australians use ancient DNA to solve 320-year-old Falkland Islands wolf mystery

An illustration of the Falklands Islands Wolf by
Michael Rothman for Ace Coinage.

University of Adelaide researchers have found the answer to one of natural history's most intriguing puzzles - the origins of the now extinct Falkland Islands wolf and how it came to be the only land-based mammal on the isolated islands - 460km from the nearest land, Argentina.

Previous theories have suggested the wolf somehow rafted on ice or vegetation, crossed via a now-submerged land bridge or was even semi-domesticated and transported by early South American humans.

The 320-year-old mystery was first recorded by early British explorers in 1690 and raised again by Charles Darwin following his encounter with the famously tame species on his Beagle voyage in 1834.

Researchers from the University's Australian Centre for Ancient DNA (ACAD) extracted tiny pieces of tissue from the skull of a specimen collected personally by Darwin. They also used samples from a previously unknown specimen, which was recently re-discovered as a stuffed exhibit in the attic of Otago Museum in New Zealand.

The findings were published in Nature Communications today and concluded that, unlike earlier theories, the Falkland Islands wolf (Dusicyon australis) only became isolated about 16,000 years ago around the peak of the last glacial period.

"Previous studies used ancient DNA from museum specimens to suggest that the Falkland Islands wolf diverged genetically from its closest living relative, the South American maned wolf (Chrysocyon brachyurus) around seven million years ago. As a result, they estimated that the wolf colonised the islands about 330,000 years ago by unknown means," says Associate Professor Jeremy Austin, Deputy Director of ACAD and co-lead author with Dr Julien Soubrier.

"Critically, however, these early studies hadn't included an extinct relative from the mainland, the fox-like Dusicyon avus. We extracted ancient DNA from six specimens of D. avus collected across Argentina and Chile, and made comparisons with a wide group of extinct and living species in the same family."

ACAD's analyses showed that D. avus was the closest relative of the Falkland Islands wolf and they separated only 16,000 years ago - but the question of how the island colonisation came about remained. The absence of other mammals argued against any land bridge connection to the mainland.

"The Eureka moment was finding evidence of submarine terraces off the coast of Argentina," says study leader Professor Alan Cooper. "They recorded the dramatically lowered sea levels during the Last Glacial Maximum (around 25-18,000 years ago)."

"At that time, there was a shallow and narrow (around 20km) strait between the islands and the mainland, allowing the Falkland Islands wolf to cross when the sea was frozen over, probably while pursuing marine prey like seals or penguins. Other small mammals like rats weren't able to cross the ice."

Disease not a factor in Tassie Tiger extinction: Adelaide University

Tasmanian Tigers at Beaumaris Zoo, Hobart c 1918.
Reproduced with permission from the Tasmanian Museum and Art Gallery
via University of Adelaide Marketing Communications team.

Humans alone were responsible for the demise of Australia's iconic extinct native predator, the Tasmanian Tiger or thylacine, a new study led by the University of Adelaide has concluded.

Using a new population modelling approach, the study contradicts the widespread belief that disease must have been a factor in the thylacine's extinction.

The thylacine was a unique marsupial carnivore found throughout most of Tasmania before European settlement in 1803. Between 1886 and 1909, the Tasmanian government encouraged people to hunt thylacines and paid bounties on over 2000 thylacine carcasses. Only a handful of animals were located after the bounty was lifted and the last known thylacine was captured from the wild in 1933.

"Many people, however, believe that bounty hunting alone could not have driven the thylacine extinct and therefore claim that an unknown disease epidemic must have been responsible," says the project leader, Research Associate Dr Thomas Prowse, School of Earth and Environmental Sciences and the Environment Institute.

"We tested this claim by developing a 'metamodel' - a network of linked species models - that evaluated whether the combined impacts of Europeans could have exterminated the thylacine, without any disease."

The mathematical models used by conservation biologists to simulate the fate of threatened species under different management strategies (called population viability analysis or PVA) traditionally neglect important interactions between species. The researchers designed a new approach to PVA that included species interactions.

"The new model simulated the directs effects of bounty hunting and habitat loss and, importantly, also considered the indirect effects of a reduction in the thylacine's prey (kangaroos and wallabies) due to human harvesting and competition from millions of introduced sheep," Dr Prowse says.

"We found we could simulate the thylacine extinction, including the observed rapid population crash after 1905, without the need to invoke a mystery disease.

"We showed that the negative impacts of European settlement were powerful enough that, even without any disease epidemic, the species couldn't escape extinction."

The study 'No need for disease: testing extinction hypotheses for the thylacine using multi-species metamodels', which also involved Professors Corey Bradshaw and Barry Brook from the University of Adelaide's Environment Institute, Professor Chris Johnson from the University of Tasmania, and Dr Bob Lacy, Chicago Zoological Society, has been published online in the Journal of Animal Ecology.