Scientists set out to investigate the ancestral biogeography of Coerebinae, including 14 closest species of Darwin's finches, to understand where these birds truly originated from.
The Coerebinae, which was discovered in the Galapagos Islands in 1835, is the living proof of Charles Darwin's theory of natural selection. Whether this species, which belongs to the family of tanagers, originated from the Galapagos or not is the subject of debate.
Using state-of-the-art statistical software, researchers at San Diego State University have put the matter to rest. Their model uses two biogeographical categories: the first group included Galapagos, South America, and the Caribbean while the second group added subregions like the Amazon or the Andes for a total of eight sub-regions.
The results showed that Darwin's finches, including 14 of its closest species, are more likely to have originated from the Caribbean and not the South America mainland, which is closer to Galapagos.
"The results were a bit surprising because they suggested a dispersal pattern that was not necessarily the most 'straightforward' explanation for how these birds arrived in the Galápagos. I think one of the big takeaway messages here is the possibility that biogeographic events, like dispersal, may not necessarily happen like logic tells us they should," Funk said.
The Evolution of Darwin's Finches
If the giant tortoise is the symbolic trademark of the Galapagos Islands, Darwin's finches prove the theory of evolution by natural selection.
He, together with an ornithologist named John Gould, examined that the finches of the Galapagos Islands are similar to the one found in mainland South America. This led the scientists to think that these finches once had their colonies on the island.
However, the finches from the two different locations share different characteristics in terms of beak shape, claw size, and overall body size. Darwin theorized that the differences in the birds may be attributed to the type and availability of food in the Galapagos.
Theory of Evolution By Natural Selection
The distance islands of the Galapagos to mainland South America may also hinder breeding across different species of finches, suggesting that the finches could have evolved over time to suit the conditions of each island.
"An ancestor to this lineage that was more likely to wander would be much more likely to encounter oceanic islands such as those of the Caribbean, with the variance in bill shape providing the means for successful colonists to adapt to open ecological niches," the authors concluded.
"An underlying genetic component would allow this dispersal propensity to persist throughout subsequent speciation events until the long-distance dispersal to, and proliferation throughout, the Galapagos Islands."
What makes this bird important to biologists is that their physical variations suggest they have evolved to outcompete and outlast other species with less advantageous characteristics; thus, proving the theory of evolution by natural selection.