July 28, 2010

Australian, South American Marsupials Share Common Ancestry

All current Australian marsupials can trace their ancestry back to South America, according to a new study by German researchers from the University of Munster's Institute of Experimental Pathology.

"While marsupials like the Australian tammar wallaby and the South American opossum seem to be quite different, research by Maria Nilsson and colleagues at the University of Munster"¦ shows otherwise," a press release dated July 27 says.

"Using sequences of a kind of 'jumping gene,' the team has reconstructed the marsupial family to reveal that all living Australian marsupials have one ancient origin in South America," it continues. "This required a simple migration scenario whereby theoretically only one group of ancestral South American marsupials migrated across Antarctica to Australia."

Previously, scientists had theorized that marsupials had originated in Australia, but that different lineages had diverged when the continent and South America separated approximately 80 million years ago, the researchers say.

Past studies on the genes of these creatures "have revealed contradictory results about which lineages are most closely related and which split off first," according to the press release, which adds that the new study shows that modern Australian marsupials "appear to have branched off from a South American ancestor to form all currently known marsupials--kangaroos, the rodent-like bandicoots, and the Tasmanian devil. It is still a mystery how the two distinct Australian and South American branches of marsupials separated so cleanly, but perhaps future studies can shed light on how this occurred."

"I think this is pretty strong evidence now for the hypothesis of a single migration [to Australia] and a common ancestor," research team member Juergen Schmitz told BBC News Environment Correspondent Richard Black on Tuesday. "Maybe it's around 30-40 million years ago, but we cannot say because jumping genes do not give this information"¦ It's now up to other people, maybe from the paleontology field, to find out when exactly it happened."

The study appears online in PLoS Biology, an open-access journal published by the Public Library of Science.


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