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An important message from the DNA of an extinct marsupial

Friday 16th January 2009

Thylacine - last known individual, 1936

At the end of 2008, a group of scientists made headlines when they published the near-complete DNA sequence of the extinct woolly mammoth. Now the same techniques have been used to map a significant portion of the genes belonging to the Tasmanian tiger, or thylacine, a dog-like marsupial hunted to extinction less than a century ago.

The genetic material was obtained from the hair of two preserved thylacines held for over 100 years in separate museums in Sweden and the US. When compared against each other, the two animals were found to share almost identical DNA, indicating that at the time of extinction there was very little variation in the thylacine gene pool.

Low genetic diversity and the consequential inability to adapt to environmental stresses is often cited as one of the key ingredients for species extinction. Significantly, the findings of the thylacine study provide direct evidence of low levels of genetic diversity accompanying an extinction event. For conservationists, it highlights the importance of using genetic tools to assess the vulnerability of extant species.

Early research by the same team of scientists indicates that the Tasmanian devil is one species for which low genetic variation is becoming an increasing concern. Over the last ten years the global population of this species has declined by more than 60 percent due to an infectious facial cancer. Accordingly, its conservation status was moved from Least Concern to Endangered on the 2008 IUCN Red List.

Naturally, the current wave of genetic research has led to speculation that eventually cloning techniques will be used to bring extinct animals back to life. Amongst the popular favourites for resurrection are species such as the woolly mammoth, sabre-tooth tiger, giant sloth or thylacine. Below is a selection of some less ‘charismatic’ species, arguably equally deserved of a new life in the 21st century:

Southern gastric-brooding frog (Rheobatrachus silus)

The southern gastric-brooding frog was an Australian frog with an extraordinary method of parental care. Following mating, the female would swallow the eggs so that the larvae could develop in her stomach, and then regurgitate them back up once they had metamorphosed into frogs. This curious species was only discovered in 1973 but sadly vanished from the wild a decade later.

Laysan crake (Porzana palmeri)

The Laysan crake was a small flightless member of the rail family endemic to Laysan Island in the Hawaiian archipelago. It went extinct in 1944 following human disturbance and the introduction of non-native species.

Partula snails (Partula spp.)

image: Sutural partula (Partula suturalis)

Partula snails are a fascinating genus of hermaphroditic mollusc that once comprised around 100 species, all occupying different ecological niches on numerous Pacific Ocean islands. Following the introduction of a predatory carnivorous snail to some of these islands, 50 species have gone extinct and another 14 are now extinct in the wild.

Visit MyARKive to see a selection of images and videos in the Extinct Animals scrapbook.

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