Bird evolution in Asia shaped in part by giant plateau, study finds

Colorado Arts and Science Magazine Highlight 

THURSDAY, NOVEMBER 21, 2019 

A new large-scale study from CU Boulder and colleagues provides first evidence that a gargantuan, inhospitable plateau in Asia maintains the species barriers of some birds​ 

Colorado Arts and Sciences Magazine

In the middle of Asia, there is a vast, high-altitude desert that not only helped shape the evolution of barn swallows—and likely other birds, too—but continues to keep them distinct by altering migration paths, according to new research from the University of Colorado Boulder. 

These new findings, published this week in the journal Ecology Letters, provide the most-convincing evidence yet for a long-held hypothesis that the Tibetan plateau is an important catalyst and maintainer of the vast diversity of birds found in Asia. It does this by being a barrier that keeps them separate, sending some migrating birds to Africa and others to south and southeast Asia. 

“What we’re getting is a really consistent snapshot that different subspecies (of barn swallows), when they come together, are responding in the same way to a major geographic barrier,” said Rebecca Safran, an associate professor of ecology and evolutionary biology at the University of Colorado Boulder and a senior author on the paper. 

“It suggests that there’s something universal about that place on planet Earth that at least different subspecies of barn swallows are responding to by migrating in different directions above it.” 

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Bird evolution unique in seeing shrinking testes

DECEMBER 3, 2019 

Birds are the only group of vertebrate animals to have repeatedly evolved smaller testes over time according to a new study. 

A paper published in Ecology Letters by University of Reading researchers and colleagues has found that natural selection has led to smaller testes sizes among socially monogamous birds. The team suggest that the developments of mating behavior in birds may have led to an evolutionary loop that has led to smaller testes. 

Dr. Joanna Baker, a research fellow at the University of Reading, said, "Rapidly shrinking testes may have happened as a result of the fantastic diversity of behaviors and traits we observe in birds today: from beautiful plumage colorations in birds of paradise, elaborate dancing displays in songbirds, through to dedicated parental care through extreme weather conditions in penguins. 

"Bigger testes produce more sperm and so give animals a competitive advantage over their relatives with smaller testes, but are also very expensive to grow and maintain. Around 90% of birds are socially monogamous—where producing more sperm doesn't really matter—and so there has been lots of opportunity to reduce testes size in favor of other adaptations." 

No other vertebrate group, including mammals, frogs, fish, and reptiles showed any similar pattern to birds. Although lots of frogs are socially monogamous, unlike birds, they tend to be external fertilizers, so producing lots of sperm is probably still likely to produce extreme competitive advantages. 

In all vertebrates, testes size is astonishingly diverse, with enormous explosions of testes size change—both reductions and enlargements—during the last 400 million years of vertebrate evolutionary history. 

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Egg collector's hoard to help study of evolution

19/09/2019

A clutch of thousands of rare birds eggs, seized from an illegal Norfolk collector, are set to help with research into the evolution of birds after being donated to a national museum.

Daniel Lingham, 65, was sentenced to 18 weeks' imprisonment in November last year after more than 5,000 eggs were found at his home in Newton St Faith. He was also ordered to hand his entire collection of eggs to the Natural History Museum – where they are now set to provide researchers with insights into how egg shapes and sizes have evolved over time.

A researcher from the museum told BBC Radio Norfolk: "We're about to use these three clutches of lapwing eggs in a major study on the evolution of egg shape and size. One of the things that the team is most interested in is the changes over time."

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Scientists make new discovery about bird evolution

March 24, 2017

In a new paper published in National Science Review, a team of scientists from the Institute of Vertebrate Paleontology and Paleoanthropology, the Shandong Tianyu Museum of Nature, and the Nanjing Institute of Geology and Paleontology (all in China) described the most exceptionally preserved fossil bird discovered to date.

The new specimen from the rich Early Cretaceous Jehol Biota (approximately 131 to 120 million years old) is referred to as Eoconfuciusornis, the oldest and most primitive member of the Confuciusornithiformes, a group of early birds characterized by the first occurrence of an avian beak. Its younger relative Confuciusornis is known from thousands of specimens but this is only the second specimen of Eoconfuciusornis found. This species comes only from the 130.7 Ma Huajiying Formation deposits in Hebei, which preserves the second oldest known fossil birds. Birds from this layer are very rare.

This new specimen of Eoconfuciusornis, housed in the Shandong Tianyu Museum of Nature, in Eastern China, is a female. The ovary reveals developing yolks that vary in size, similar to living birds. This suggests that confuciusornithiforms evolved a period of rapid yolk deposition prior to egg-laying (crocodilians, which are archosaurs like birds, deposit yolks slowly in all eggs for months with no period of rapid yolk formation), which is indicative of complex energetic profiles similar to those observed in birds.

This means Eoconfuciusornis and its kin, like living birds, was able to cope with extremely high metabolic demands during early growth and reproduction (whereas energetic demands in crocodiles are even, lacking complexity). In contrast, other Cretaceous birds including the more advanced group the Enantiornithes appear to have lower metabolic rates and have required less energy similar to crocodilians and non-avian dinosaurs (their developing yolks show little size disparity indicating no strong peak in energy associated with reproduction, and much simpler energetic profiles, limited by simpler physiologies).

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Shape of bird wings depends on ancestors more than flight style

In a finding that could change the way scientists think about bird evolution, researchers have found that the shape of bird wings is influenced more by how closely related species are to one another than by flight style.

The research challenges scientific beliefs that assume the way a bird species flies--whether it primarily dives, glides or flaps, for instance--plays the primary role in the evolution of its wing shape. It also indicates that it may be more difficult than previously thought to infer flying behaviors of early birds and the first flying dinosaurs from fossils alone.

Julia Clarke, an associate professor in the Department of Geological Sciences at The University of Texas Jackson School of Geosciences, conducted the work with Xia Wang, a post-doctoral researcher who led the study. Their research was published in the journal Proceedings of the Royal Society B: Biological Sciences in October.

Bird wings, unlike stiff airplane wings, are flexible and change shape during flight. So, their geometry and wing outline may not tell the whole story of a particular flight style or environment, Clarke said.

"We've taken a lot for granted. Birds are not airplanes," Clarke said.

By comparing geometry across species and clades - groups of organisms that evolved from a common ancestor - the researchers found that birds that are closely related evolutionarily have similar wing structures, even if the birds show very different flight styles. For example, albatrosses, penguins and loons, despite looking very different from one another, all belong to the clade Aequornithes and have a wing shape that is very similar.

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'Big Bang' of bird evolution mapped: Genes reveal deep histories of bird origins, feathers, flight and song

Date:

December 11, 2014

Source:

Duke University

Summary:

The first findings of the Avian Phylogenomics Consortium are being reported nearly simultaneously in 29 papers -- eight papers in a Dec. 12 special issue of Science and 21 more in Genome Biology, GigaScience and other journals. The analyses suggest some remarkable new ideas about bird evolution, including insights into vocal learning and the brain, colored plumage, sex chromosomes and the birds' relationship to dinosaurs and crocodiles.

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