Remains of a giant short-faced kangaroo (Simosthenurus occidentalis) and a giant wallaby (Protemnodon anak) were found in a cold, dry cave in Tasmania.
They had perished around 45,000 years ago, but favourable conditions in the high-altitude, high-latitude cave meant the specimens were still relatively well preserved.
This allowed a team of scientists led by Dr Bastien Llamas and Professor Alan Cooper from the University of Adelaide's Australian Centre for Ancient DNA (ACAD) to extract DNA sequences from the two species.
“The ancient DNA reveals that giant wallabies are very close relatives of large living kangaroos, such as the red and western grey kangaroos,” says lead author and ACAD senior research associate Dr Bastien Llamas.
“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 team recovered partial “mitochondrial genomes” – genetic material transmitted from mother to offspring. It's widely used in determining evolutionary relationships.
DNA from the giant short-faced kangaroos has confirmed they are a highly distinct lineage of macropods, which had been predicted on their unusual anatomy.
Poor preservation conditions and extreme age of megafaunal remains in Australia has prevented retrieval of DNA until now, with scientists relying on bones to determine their evolutionary relationships.
For example, the banded hare-wallaby, an elusive species that lives on isolated islands off the coast of Western Australia, has emerged as the last living relative of the ancient short-faced kangaroos. That information was not supported by recent morphological phylogenetic analyses – but the ancient DNA recovered in this study backs the idea.
“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,” says Dr Llamas.
“Together with my colleagues Alan Cooper and Paul Brotherton, we had to think hard about experimental and bioinformatics approaches to overcome more than 10 million years of divergent evolution between the extinct and living species.”
The research is published online in Molecular Biology and Evolution.Jump to next article