When Charles Darwin made his now infamous trip to the Galapagos Islands in the early 19th century, he made a trivial observation that would nevertheless end up profoundly changing our understanding of the natural world. He noticed that the beak shapes of birds differed drastically from island to island. For example, cactus finches had longer, pointed beaks than ground finches, and warbler finches had thinner and more pointed beaks than both. The question, of course, was what led to this variation and pondering this question would eventually lead Darwin to the theory of evolution for which he is now famous.
Yet 180-odd years after Darwin circumnavigated the globe on the HMS Beagle, researchers are still investigating how bird beaks came to be so diverse. Most recently, researchers at the University of Sheffield have enlisted the public's help in measuring 3D scans of bird beaks from over 2,000 species kept in London's Natural History Museum and the Manchester Museum. Based on this crowdsourced data, the researchers hoped to discover how bird beaks evolved over time.
"This project has given us key insight into how evolutionary processes play out over millions of years, with major bursts of evolution as new groups emerge, and more fine scale changes thereafter," said Gavin Thomas, a professor of animal and plant sciences at the University of Sheffield. "With the efforts of our volunteers from across the world, the study has given us a unique new data set for the study of bird ecology and evolution."
As detailed in an accompanying paper published Wednesday in Nature, the public was able to participate in data collection by accessing thousands of bird beaks 3D scanned from specimens housed in the two museums and then uploaded to an online database. Here the public would help by "landmarking" aspects of the different bird beaks, marking areas like the front, back and tip of the beak for each specimen. By comparing these details to where a bird sits on its family tree, the researchers were able to determine the way these beaks had evolved over time.
What they found was that the diversity of bird beaks expanded early on in their evolutionary history. The more extreme beak shapes were the products of extremely rapid evolutionary change, but these beak changes became more subtle as the birds filled increasingly specific ecological niches. However in isolated areas like the Galapagos or Hawaiian islands, bird beaks continue to evolve rapidly.
"It's striking how much the speed of evolution changes between different birds," said Jen Bright, an assistant professor of evolutionary biology at the University of South Florida. "It's a really dynamic process, and it means there are still lots of questions left to answer about how birds managed to come up with the range of beak shapes that they have."
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