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A team of inter­na­tional sci­en­tists have dis­cov­ered the unique Tas­man­ian Tiger or thy­lacine had lim­ited genetic diver­sity prior to its extinc­tion. The results pub­lished today in the inter­na­tional jour­nal PLoS One,

pro­vide insights into the genetic health of the thy­lacine (Thy­lac­i­nus cyno­cephalus) before it was exter­mi­nated by hunting.

Lead author Dr Bran­don Men­zies, an Hon­orary Fel­low of the Uni­ver­sity of Mel­bourne, who com­pleted the study at the Leib­niz Insti­tute for Zoo and Wildlife Research in Berlin with an Alexan­der von Hum­boldt post-​doctoral fel­low­ship, said the lat­est study revealed that the Tas­man­ian Tiger had the same or even less genetic diver­sity than its close rel­a­tive the Devil. “Hence, Tas­man­ian Tigers may have faced sim­i­lar envi­ron­men­tal prob­lems to the Dev­ils, had they sur­vived,” Dr Men­zies said.

“Due to the sim­i­larly poor genetic diver­sity of the ani­mals, this new data sug­gests that the genetic health of the Tas­man­ian Tiger and Devil may have been affected by the geo­graphic iso­la­tion of Tas­ma­nia from main­land Aus­tralia approx­i­mately 10 – 13 thou­sand years ago,” he said. The thy­lacine has been the focus for biol­o­gists due to its unique evo­lu­tion in Aus­tralia and extinc­tion. Hav­ing evolved from a mar­su­pial into a mam­mal that is very sim­i­lar to a dog or wolf, but being mar­su­pi­als, the females had a pouch in which they car­ried their young.

Dr Men­zies said that while the thy­lacine was hunted to extinc­tion due to the impo­si­tion of a gov­ern­ment bounty from 1888 – 1909, one ques­tion that con­tin­ued to puz­zle biol­o­gists was how genet­i­cally diverse the thy­lacine pop­u­la­tion was prior to its extinc­tion. The last known ani­mal died in cap­tiv­ity at the Tasmanian’s Beau­maris Pri­vate Zoo in Hobart, Aus­tralia on the 7^th Sep­tem­ber 1936, although the species was not offi­cially declared extinct by inter­na­tional stan­dards in 1986.

Using a com­bi­na­tion of tra­di­tional DNA sequenc­ing meth­ods and next gen­er­a­tion sequenc­ing tech­nol­ogy, a team of inter­na­tional sci­en­tists led by Dr Bran­don Men­zies, and Dr Andrew Pask, from the Uni­ver­sity of Con­necti­cut, who also holds a frac­tional appoint­ment at the Uni­ver­sity of Melbourne’s Zool­ogy Depart­ment, demon­strated the very lim­ited DNA vari­abil­ity between indi­vid­ual thy­lacine specimens.

Dr Men­zies »

With con­tri­bu­tions from sci­en­tists in Ger­many, the USA and Aus­tralia, researchers com­pared mito­chon­dr­ial DNA extracted from 14 museum spec­i­mens that were between 102 – 159 years old. The results revealed the thy­lacine spec­i­mens were more than 99.5 per cent sim­i­lar over a por­tion of DNA that is nor­mally highly vari­able between indi­vid­ual ani­mals. In a direct com­par­i­son with other species, the thy­lacine aver­ages about 5 – 10 DNA base dif­fer­ences over the cod­ing sec­tions of the mito­chon­dr­ial genome. This is quite low when com­pared to other species includ­ing the wolf (77) or African humans (85). The Tas­man­ian Devil has about 10 DNA dif­fer­ences between indi­vid­u­als over the whole genome, which is also low.

“This work high­lights our need to under­stand all of Tasmania’s and Australia’s unique flora and fauna so they are also not lost to extinc­tion,” he said. “This new study con­firms the rel­a­tively low genetic diver­sity in the Tas­man­ian Tiger which sadly was hunted to extinc­tion. We can­not bring the Tiger back to life, but at least we can con­tinue to learn as much as pos­si­ble about these iconic mar­su­pial carnivores.”?

The above news item is reprinted from mate­ri­als avail­able at The Mel­bourne News­room via Sci­enceDaily. Orig­i­nal text may be edited for con­tent and length.

(Sources: The Mel­bourne News­room, 19.04.2012; Forschungsver­bund Berlin e.V., 18.04.2012)