Demise of the Tasmanian Tiger
By tony leather, 15th Jul 2012 | Follow this author
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Recent research, newly published, indicates that Tasmanian tigers -, thylacines - had, immediately prior to humans hunting it to extinction, very low genetic variability.
Demise of the Tasmanian Tiger
On the South Australian island of Tasmania, many strange creatures evolved, perhaps most famously the enigmatic Tasmanian tiger - a dog-resembling marsupial that went extinct - something that could easily happen with the endangered Tasmanian devil as well.
Recent research, newly published, indicates that Tasmanian tigers -, thylacines - had, immediately prior to humans hunting it to extinction, very low genetic variability. This meant that there simply had not been enough genetic diversification, limiting possible beneficial gene copy pools within the population as a whole.
Tasmanian devils, living cousins to the extinct tigers, display the same genetic tendencies, rendering it vulnerable to a form of contagious cancer that is decimating the species so much that Tasmanian devil populations, over the past 15 years have decreased dramatically, by up to 90% some parts of the island
Tasman2
Researchers conducting the study looked at preserved specimens of the Tasmanian tiger, including pelts and bones f more than 100 century old - last living example died in a Tasmanian zoo in 1936 - scientists finding individuals with 99.5% similarity in part of the DNA that is normally highly variable, as well as a 99.9% similarity to previously published mitochondrial genome of the animal.
These results demonstrate just how limited genetic diversity of the tiger was, perhaps because the submerging of the land bridge between the island and Australia, ten thousand years earlier, had led to a disastrous cutting off of inter-breeding opportunities for the entire tiger population spread between the two places.
Tasmanian tigers, devils and of course many other species became geographically isolated from Australian counterparts, added to which. in 1888, the Tasmanian government in placed a bounty on thylacines, which were believed to prey on sheep, though there was never any hard evidence to support this fear.
Nonetheless, local farmers and others took up the call with enthusiasm, and by the time it was realised that a mistake had been made, wild Tasmanian tigers had been consigned to history, though DNA from this extinct creature might help to unravel the horrific disease problems plaguing the Tasmanian devil.
The facial tumour disease - an unusual transmissible cancer only recently evolved in Tasmania - is spread by the creatures biting one other during social inter-actions, and has a 100% mortality rate, very few resistant animals identified to date, so captive breeding of unaffected animals is the best option for saving the species
Extremely low genetic diversity problems are disastrous for any species, rendering them less able to adapt to change, and making the species susceptible to ultimate extinction, if steps are not taken. To this end, more studies on Tasmanian tiger remains are planned.
Though a marsupial, the internal body design of the tiger was so dog-like that even, to this day, most archaeologists cannot separate the two skeletons, the two having last shared a common ancestor around 160 million years ago, which had had an opossum-like body.
Even though thylacine and dog went separate evolutionary ways, they had similar modes of existence, both being nomadic hunters eating small mammals. This similarity provides an absolutely opportunity for researchers to investigate how evolution occurs at the genome level, a team currently sequencing the complete thylacine genome, to help in address this fascinating puzzle.
Tasman3
Nonetheless, local farmers and others took up the call with enthusiasm, and by the time it was realised that a mistake had been made, wild Tasmanian tigers had been consigned to history, though DNA from this extinct creature might help to unravel the horrific disease problems plaguing the Tasmanian devil.
The facial tumour disease - an unusual transmissible cancer only recently evolved in Tasmania - is spread by the creatures biting one other during social inter-actions, and has a 100% mortality rate, very few resistant animals identified to date, so captive breeding of unaffected animals is the best option for saving the species
Extremely low genetic diversity problems are disastrous for any species, rendering them less able to adapt to change, and making the species susceptible to ultimate extinction, if steps are not taken. To this end, more studies on Tasmanian tiger remains are planned.
Tasman4
Though a marsupial, the internal body design of the tiger was so dog-like that even, to this day, most archaeologists cannot separate the two skeletons, the two having last shared a common ancestor around 160 million years ago, which had had an opossum-like body.
Even though thylacine and dog went separate evolutionary ways, they had similar modes of existence, both being nomadic hunters eating small mammals. This similarity provides an absolutely opportunity for researchers to investigate how evolution occurs at the genome level, a team currently sequencing the complete thylacine genome, to help in address this fascinating puzzle.
Comments
15th Jul 2012 (#)
Tony Great piece really enjoyed
Best Wishes
Steve
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