Finches, the same birds that so intrigued Darwin, have been an asset to evolutionary science yet again.
Peter and Rosemary Grant have spent much of the last 36 years studying these birds, and have been lucky enough to witness a case of species divergence.
It all started with a finch that migrated from a neighboring island. He was slightly larger than the native finches, and had a slightly different beak and song pattern, though he tried to mimic the natives as best he could. He mated, with a female that also had some hybrid genes, and taught his offspring his slightly different song.
That might have been the end of it, but for a drought that happened four generations later, killing all of the line but a brother and sister. They mated, as did their offspring. After at least three incestuous generations, this lineage was determined to be isolated enough from the native finches' gene pool to be its own species.
In the future, this tiny new species may be no more: it may breed its way back into the mainstream, be out-competed by the natives, or be done in by their inbreeding magnifying genetic flaws. Only time will tell.
Image: "Medium ground finch Santa Cruz" by putneymark on Flickr courtesy of Creative Commons Licensing.Tweet