domenica 10 marzo 2013


Falkland Islands Wolf Mystery Solved

Sarah C.P. Williams

By comparing DNA from Falkland Island wolves and an extinct mainland species, scientists now believe they know how the only native mammal arrived on the island. Learn more...

The Falkland Islands wolf, known scientifically as Dusicyon australis, was the only mammal native to the islands before its extinction. The wolves were observed by sailors in the 17th century and written about by Charles Darwin, who wondered how the species had come to be on the islands. Some theorized that humans brought the wolves to the islands or that the wolves crossed a land bridge or were transported by ice floes.But now a new genetic analysis of the Falkland Islands wolf has revealed that the species split from its mainland ancestors approximately 16,000 years ago. The new findings put the arrival of the wolf on the islands much later in history than previous data and support a theory that the wolves could have crossed to the Falklands over ice straits during the last ice age.
“Getting that time frame gave us a big clue,” said Alan Cooper, director of the Australian Centre for Ancient DNA at the University of Adelaide, who led the new research. “We know that the sea was very low at that time because of all the icecaps.”
A 2009 study discovered that the closest living relative to the Falkland wolf is the South American maned wolf, which dispelled the theory that the wolves were descendants of domesticated dogs. But the study didn’t pin down the exact timeline for the Falkland Island wolves’ origin since they diverged from the maned wolves around seven million years ago. “The trouble was that these wolves were really very distantly related,” said Cooper.
So in the new work, rather than only looking at living species, Cooper’s team added data on an extinct fox, Dusicyon avus, which lived on mainland South America until about 3000 years ago. The researchers obtained seven samples of D. avus DNA and sequenced the mitochondrial genes COII and cytochrome b. Then the team constructed a phylogeny, fitting both D. avusand the Falkland Island wolf into the family tree. As a result, the lab found that the two species diverged around 16,000 years ago.
With that new timeline in hand, Cooper and his colleagues turned to the literature on the geology of the area. “We found studies showing terraces along the currently submerged coastline,” said Cooper. “And those terraces record where the shoreline was for a long period of time.”
Cooper found that during the ice age the oceans were 130 meters lower than their present levels, and the gap between present day Argentina and the Falkland Islands would have measured 20 to 30 kilometers across and only 10 to 30 meters deep. At times, it’s likely that the shallow water completely froze over. While rodents and herbivores would not have been able to cross the long expanses of ice, wolves could have survived by hunting seals, penguins, and other seabirds.
“I think we’ve nailed it now,” said Cooper. “We’re not planning on doing much more on this question at this point.”
  1. Austin JJ, Soubrier J, Prevosti FJ, Prates L, et al. The origins of the enigmatic Falkland Islands wolf (2013). Nature Communications 4, 1552.

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