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Darwin's finches don't tell the whole story of avian evolution

University College London

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IMAGE: This shows the very different skull shape in four different bird species that all eat the same diet: aquatic animals. Despite eating similar diets, they acquire their prey in very... view more 

Credit: Dr. Ryan Felice, UCL

The connection between bird diet and skull shape is surprisingly weak for most species according to a new study led by UCL and the Natural History Museum, rewriting our understanding of how ecosystems influence evolution.

Charles Darwin's 19th century observations of finches on the Galápagos Islands concluded that bird speciation was primarily influenced by ecosystem; the way a bird forages and eats forms its skull shape and drives evolutionary change.

However, a new study by UCL and NHM researchers testing a wider range of species than ever before has found that on a global scale, shared ancestry and behaviour are more important factors than diet.

The study, published in Royal Society journal Proceedings B, tested the skull shape of 352 bird species, representing 159 out of the 195 existing families, making it the largest study of its kind.

"If we apply Darwin's conclusion for different kinds of birds who primarily eat fish, pelicans and penguins should have exactly the same head and beak shape, as they both use their beaks to eat fish. However, pelicans have a long beak and large throat pouch, while penguins' beaks are comparatively small," explained Dr Ryan Felice (UCL Biosciences), one of the authors of the study.

"Although they eat the same thing, pelicans and penguins acquire their prey in different ways, demonstrating the important role behaviour plays in cranial evolution."

Penguins' mouths have a series of spines pointing down their throats, so that food stays in there when caught. Pelicans ingeniously catch fish in their pouch and then tip it back to drain out the water and swallow the fish immediately.

"It is evolutionary history, rather than diet, that has most significantly influenced cranial shape. If you are descended from a duck-like ancestor, you will probably have a duck bill, no matter what diet you have. However, shared diet establishes the parameters of skull evolution, determining the range of potential shapes which can evolve," added Dr Felice.

The researchers also discovered that birds who eat grains - such as finches and quail - and those who survive on the nectar of flowers - like hummingbirds - exhibit the highest rate of cranial evolution. By contrast, terrestrial carnivores - hawks, falcons, owls and other birds who hunt and eat using their talons - exhibit a very slow rate of cranial change.

"This is where natural selection comes into play," said Professor Anjali Goswami, a Research Leader at the Natural History Museum and a co-author on the study.

"Birds that eat nectar or seeds are going to experience lots of competition for resources and must evolve in order to survive."

"Our study focused on the skull, but we hypothesise that other parts of the body could be shaped by diet and ecology, such as wings, talons, and stomachs, as these are the parts of their bodies which are crucial for catching and digesting prey."

The study used state-of-the-art equipment to build high resolution 3D digital models of the bird skulls. This allowed researchers to plot many more points on the skull than previously possible, allowing them to make robust and accurate measurements.

"Our next step is to expand this analysis to other groups of animals, like mammals, reptiles, and dinosaurs," said Dr. Felice. "Our goal is to understand all of the different factors that have shaped skull evolution through time."

Dr Felice's partners on the paper were Dr Joseph Tobias (Imperial College London), Dr Alex Pigot (UCL Biosciences) and Professor Anjali Goswami (UCL Biosciences & Natural History Museum).

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This study was funded by the European Research Council, the Natural Environment Research Council (NERC) and SYNTHESIS.

Note to editor

For more information or to speak to those involved, please contact: Tash Payne, UCL Media Relations. T: +44 (0)20 3108 9243, E: tash.payne@ucl.ac.uk

Ryan N. Felice, Joseph A. Tobias, Alex L. Pigot and Anjali Goswami, 'Dietary niche and the evolution of cranial morphology in birds' will be published in Proceedings B on Wednesday 20 February 2018, 00.01 UK time and is under a strict embargo until this time.

The DOI for this paper will be http://dx.doi.org/10.1098/rspb.2018.2677.

Additional material

Images available for download at the following link: https://www.dropbox.com/s/ucqdpg1tb82hs2b/Darwin%20bird%20skull%20evolution%20press%20release%20image.tiff?dl=0

About UCL (University College London)

UCL was founded in 1826. We were the first English university established after Oxford and Cambridge, the first to open up university education to those previously excluded from it, and the first to provide systematic teaching of law, architecture and medicine. We are among the world's top universities, as reflected by performance in a range of international rankings and tables. UCL currently has over 41,500 students from 150 countries and over 12,500 staff. http://www.ucl.ac.uk | Follow us on Twitter @uclnews | Watch our YouTube channel YouTube.com/UCLTV

The Natural History Museum

The Natural History Museum exists to inspire a love of the natural world and unlock answers to the big issues facing humanity and the planet. It is a world-leading science research centre, and through its unique collection and unrivalled expertise it is tackling issues such as food security, eradicating diseases and managing resource scarcity. The Natural History Museum is the most visited natural history museum in Europe and the top science attraction in the UK; we welcome around five million visitors each year and our website receives over 500,000 unique visitors a month. People come from around the world to enjoy our galleries and events and engage both in-person and online with our science and educational activities through innovative programmes and citizen science projects.

Natural Environment Research Council

NERC is the UK's main agency for funding and managing research, training and knowledge exchange in the environmental sciences. Our work covers the full range of atmospheric, Earth, biological, terrestrial and aquatic science, from the deep oceans to the upper atmosphere and from the poles to the equator. We coordinate some of the world's most exciting research projects, tackling major environmental issues such as climate change, environmental influences on human health, the genetic make-up of life on Earth, and much more. NERC is part of UK Research & Innovation, a non-departmental public body funded by a grant-in-aid from the UK government.

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