Brandon Keim reports in Wired:
On one of the Galapagos islands whose finches shaped the theories of a young Charles Darwin, biologists have witnessed that elusive moment when a single species splits in two.
In many ways, the split followed predictable patterns, requiring a hybrid newcomer who’d already taken baby steps down a new evolutionary path. But playing an unexpected part was chance, and the newcomer singing his own special song.
This miniature evolutionary saga is described in a paper published Monday in the Proceedings of the National Academy of Sciences. It’s authored by Peter and Rosemary Grant, a husband-and-wife team who have spent much of the last 36 years studying a group of bird species known collectively as Darwin’s finches.
The finches — or, technically, tanagers — have adapted to the conditions of each island in the Galapagos, and they provided Darwin with a clear snapshot of evolutionary divergence when he sailed there on the HMS Beagle. The Grants have pushed that work further, with decades of painstaking observations providing a real-time record of evolution in action. In the PNAS paper, they describe something Darwin could only have dreamed of watching: the birth of a new species.
The species’ forefather was a medium ground finch, or Geospiza fortis, who flew from a neighboring island to the Grants’ island of Daphne Major, and into their nets, in 1981. He “was unusually large, especially in beak width, sang an unusual song” and had a few gene variants that could be traced to another finch species, they wrote. This exotic stranger soon found a mate, who also happened to have a few hybrid genes. The happy couple had five sons…
[continues in Wired]
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