Australian researchers have managed to extract DNA from two extinct marsupials: a giant short-faced kangaroo (Simosthenurus occidentalis) and a giant wallaby (Protemnodon anak).
Giant wallaby (Protemnodon anak). Image credit: Nobu Tamura / CC BY 3.0.
“The ancient DNA reveals that extinct giant wallabies are very close relatives of large living kangaroos, such as the red and western grey kangaroos,” said Dr Bastien Llamas of the University of Adelaide’s Australian Cente for Ancient DNA, who is the first author of a paper published in the journal Molecular Biology and Evolution.
The two specimens, Simosthenurus occidentalis and Protemnodon anak, have been radiocarbon dated to approximately 45,000 years ago.
Their remains were discovered in a cold and dry cave in Tasmania. Relatively good preservation conditions in the cave allowed enough short pieces of DNA to survive so researchers could reconstruct partial mitochondrial genomes – genetic material transmitted from mother to offspring and widely used to infer evolutionary relationships.
“Their skeletons had suggested they were quite primitive macropods a group that includes kangaroos, wallabies, pademelons and quokkas – but now we can place giant wallaby much higher up the kangaroo family tree.”
The study has also confirmed that short-faced kangaroos are a highly distinct lineage of macropods, which had been predicted on their unusual anatomy.
Generally poor preservation conditions and the age of Australian megafaunal remains has prevented retrieval of its DNA until now, although complete nuclear or mitochondrial genomes have been previously obtained from extinct megafauna from Eurasia, the Americas, and New Zealand.
Scientists attempting to decipher the evolutionary relationships of the Australian megafauna were previously restricted to using information from bones.
“In addition to poor DNA preservation, most of the extinct Australian megafauna do not have very close relatives roaming around today, which makes it more difficult to retrieve and interpret the genetic data,” Dr Llamas said.
Although ancient DNA confirms that the short-faced kangaroos left no descendants, it also shows their closest living cousin could be the banded hare-wallaby (Lagostrophus fasciatus), which is now restricted to small isolated islands off the coast of Western Australia.
“Our results suggest the banded hare-wallaby is the last living representative of a previously diverse lineage of kangaroos,” said co-author Prof Mike Lee of the South Australian Museum and the University of Adelaide’s School of Biological Sciences.
“It will hopefully further encourage and justify conservation efforts for this endangered species.”
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Bastien Llamas et al. Late Pleistocene Australian Marsupial DNA Clarifies the Affinities of Extinct Megafaunal Kangaroos and Wallabies. Mol Biol Evol, published online December 18, 2014; doi: 10.1093/molbev/msu338
