DNA extracted from extinct giant kangaroos

South Australian scientists have succeeded in extracting DNA sequences from two species of the country’s extinct kangaroos - the giant short-faced kangaroo (Simosthenurus occidentalis) and the giant wallaby (Protemnodon anak). The results of their research have been published in the journal Molecular Biology and Evolution.

“Understanding the evolution of Australia’s extinct marsupial megafauna has been hindered by a relatively incomplete fossil record and convergent or highly specialized morphology, which confound phylogenetic analyses,” the authors said. “Further, the harsh Australian climate and early date of most megafaunal extinctions (39-52 ka) means that the vast majority of fossil remains are unsuitable for ancient DNA analyses.”

Fossils of the two giant kangaroos were discovered in a cold and dry cave in Tasmania, whose relatively good preservation conditions allowed enough short pieces of DNA to survive. The specimens were dated to be around 45,000 years old - “significantly older than any Australian fossil that has previously yielded DNA sequence information”, according to the researchers.

“Processing the raw sequence data from these samples posed a bioinformatic challenge due to the poor preservation of DNA,” the scientists added. They were eventually able to reconstruct partial mitochondrial genomes - genetic material transmitted from mother to offspring and widely used to infer evolutionary relationships.

“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 lead author Dr Bastien Llamas from the University of Adelaide’s Australian Centre for Ancient DNA (ACAD). “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 research also confirmed that short-faced kangaroos are a highly distinct lineage of macropods, which had been predicted based on their unusual anatomy. While these kangaroos have left no descendants, the DNA 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.

“[The research] will hopefully further encourage and justify conservation efforts for this endangered species,” said co-author Professor Mike Lee, from the South Australian Museum and the University of Adelaide School of Biological Sciences.

The scientists additionally hope their findings “demonstrate the critical importance of adopting stringent processing criteria when distant outgroups are used as references for mapping highly fragmented DNA”.

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