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Consequences of Low Genetic Diversity in the Tasmanian Devil

written by: •edited by: Paul Arnold•updated: 12/4/2009

The Tasmanian devil is teetering on the brink of extinction. Its genetic diversity has been greatly diminished making it much easier for disease to take a hold. Conservationists are doing all they can stop the species from going the way of the dinosaurs.

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    Endangered Species Tasmanian Devil

    Tasmanian Devil The Tasmanian devil is a carnivorous marsupial that can now only be found in the wild in Tasmania, a large island lying to the southeast of Australia. An endangered species, it became extinct from the Australian mainland about 400 years ago and is now threatened with being wiped out altogether.

    An infectious and lethal facial cancer called devil facial tumor disease is spreading through Tasmanian devil populations. The low levels of genetic diversity mean that it's difficult for a species to survive environmental assaults or congenital diseases. Current estimates are that there are somewhere in the region of 20,000 to 50,000 Tasmanian devils in the wild and there are 500 in breeding programmes in Australian zoos and wildlife parks.

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    Low Genetic Diversity

    The cause of the low level genetic diversity in Tasmanian devils is unknown at the present time, but it makes it much harder for the animals to survive such a ferocious disease. The cancer, unlike most others, is infectious. It's believed to have started with a genetic mutation in one individual and it's passed on through bites and scratches. It takes hold very quickly and causes large tumours on the face and neck, sometimes making it impossible for an animal to eat. Some end up dying of starvation.

    To help expand Tasmanian devil genetic diversity and to prevent it from dying out, a new national project has been created. It will be led by zoologist Dr Jeremy Austin, from Adelaide University. His main task will be to try and stop the cancer in its tracks, by taking cell and tissue samples and studying the genetic material to develop a vaccine.

    The need is urgent because the cancer usually strikes before the devils reach sexual maturity, killing them off before they've had a chance to breed.

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    Immune Response

    Previous research by Sydney and Tasmania Universities found that one result of having low level genetic diversity was that the immune system of the devils was completely useless in the fight against cancer.

    An important region of the immune system, the Major Histocompatibility Complex (MHC) lost its diversity and just doesn't seem to recognise the cancer as foreign.

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    Hope for the Future

    Time is not yet up for the Tasmanian devil; this multi-pronged approach may well yield results, though of course it's too early to say. The breeding programs are a good back-up system if the vaccine approach fails. But even if it succeeds, the long term survival of the species can only be reasonably guaranteed with an expanded genetic diversity.

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    Photo

    Tasmanian Devil: http://www.flickr.com/photos/jennifrog/377342723/