November 14, 2009 | 7
While visiting the rugged Falkland Islands in the 1830s, Charles Darwin puzzled over a local wolf that was the only endemic land-dwelling mammal and looked little like other canids on the mainland. By 1876, the Falklands wolf (Dusicyon australis) was extinct and with it threatened to go its mysterious history. But a new genetic analysis of five preserved specimens, published online last week in Current Biology, has chased away speculation about these baffling animals.
"How can something the size of a Labrador retriever end up on an island in sufficient numbers that a new population emerges and evolves into a new species," Robert Wayne, a professor of ecology and biology at the University of California, Los Angeles, and co-author of the paper, noted in a prepared statement.
By sequencing part of the mitochondrial genome from preserved specimens in London, Liverpool, Philadelphia and New Zealand, the researchers discovered that the closest living relative to the Falklands wolf is the South American maned wolf (Chrysocyon brachyurus). As the paper authors noted, however, "both Darwin and [Robert] FitzRoy, [captain of the HMS Beagle on which Darwin made his famous voyage], were surprised by the striking differences between the Falklands wolf and the canids of the South American mainland," the former of which Darwin identified as a fox and the latter of which has quite long legs. The genetic analysis now pinpoints the species divergence at about 6.7 million years ago, long before either species had even migrated from North to South America.
So how did the wolves get to the isolated islands? Located about 480 kilometers from the cost of Argentina, swimming there is out of the question, and the islands themselves have never been a part of the South American mainland. The wolves must have arrived on ice floes or floating wood, the authors concluded. "A large, wolf-sized animal could perhaps live on a large iceberg with…enough prey to survive the voyage, where a vegetarian could not do that very well," Wayne said, also noting that they probably arrived on the islands "at least 70,000 years ago."
The curious canid holds a special place in the hearts of many evolutionary biologists, having been featured in Darwin’s notes from his travels on the Beagle and other early musings on evolution. After writing about the variety of animals in the Galapagos Islands, he noted: "The only fact of a similar kind of which I am aware is the constant asserted difference between the wolf-like fox of East & West Falkland [Islands]. If there is the slightest foundation for these remarks the zoology of Archipelagoes will be well worth examining; for such facts would undermine the stability of Species."
Image of the Falkland Islands wolf by George Mivart from his 1890 Dogs, Jackals, Wolves and Foxes: A Monograph of the Canidae