Songbirds’ bill colours are about social life, not sex


This 2013 video from the USA is called Bird Feeding Adaptations: How Beaks are Adapted to What Birds Eat.

From the Journal of Evolutionary Biology:

Carotenoid-based bill coloration functions as a social, not sexual, signal in songbirds (Aves: Passeriformes)

Abstract

Many animals use coloration to communicate with other individuals. While the signalling role of avian plumage colour is relatively well studied, there has been much less research on coloration in avian bare parts.

However, bare parts could be highly informative signals as they can show rapid changes in coloration. We measured bill colour (a ubiquitous bare part) in over 1600 passerine species and tested whether interspecific variation in carotenoid-based coloration is consistent with signalling to potential mates or signalling to potential rivals in a competitive context.

Our results suggest that carotenoid bill coloration primarily evolved as a signal of dominance, as this type of coloration is more common in species that live in social groups in the non-breeding season, and species that nest in colonies; two socio-ecological conditions that promote frequent agonistic interactions with numerous and/or unfamiliar individuals.

Additionally, our study suggests that carotenoid bill coloration is independent of the intensity of past sexual selection, as it is not related to either sexual dichromatism or sexual size dimorphism. These results pose a significant challenge to the conventional view that carotenoid-based avian coloration has evolved as a developmentally costly, condition-dependent sexual signal. We also suggest that bare part ornamentation may often signal different information than plumage ornaments.

Bird evolution, new research


This video says about itself:

The phylogeny of wing assisted incline running

12 January 2011

WAIR is ubiquitous among a number of avian orders, as displayed. This is not a complete sample of bird orders – the members of other orders likely perform WAIR as well. If you find video evidence, let us know!

From daily The Guardian in Britain:

Sprouting feathers and lost teeth: scientists map the evolution of birds

Mass genome sequencing reveals avian family tree – and how imitative birdsong gives birds genetic similarities to humans

A remarkable international effort to map out the avian tree of life has revealed how birds evolved after the mass extinction that wiped out the dinosaurs into more than 10,000 species alive today. More than 200 scientists in 20 countries joined forces to create the evolutionary tree, which reveals how birds gained their colourful feathers, lost their teeth, and learned to sing songs.

The project has thrown up extraordinary similarities between the brain circuits that allow humans to speak and those that give some birds song: a case of common biology being arrived at via different evolutionary routes.

Some birds are shown to have unexpectedly close relationships, with falcons more closely related to parrots than [to] eagles or vultures, and flamingoes more closely related to pigeons than [to] pelicans. The map also suggests that the earliest common ancestor of land birds was an apex predator, which gave way to the prehistoric giant terror birds that once roamed the Americas.

This video about Pleistocene prehistory in North America is called Terror Bird vs. Wolves.

“This has not been done for any other organism before,” Per Ericson, an evolutionary biologist at the Swedish Museum of Natural History in Stockholm, told the journal Science. “It’s mind-blowing.”

The scientists began their task by analysing fingernail-sized pieces of frozen flesh taken from 45 bird species, including eagles, woodpeckers, ostriches and parakeets, gathered by museums around the world over the past 30 years. From the thawed-out tissue, they extracted and read the birds’ whole genomes. To these they added the genomes of three previously sequenced species. It took nine supercomputers the equivalent of 400 years of processor time to compare all the genomes and arrange them into a comprehensive family tree.

Members of the project, named the Avian Phylogenomics Consortium, published the family tree and their analysis on Thursday in eight main papers in the journal Science, and in more than 20 others in different scientific journals.

The rise of the birds began about 65m years ago. A mass extinction – probably caused by an asteroid collision – wiped out most of the larger-bodied dinosaurs, but left a few feathered creatures. The loss of so many other species freed up vast ecological niches, giving these animals an unprecedented chance to diversify.

Comparisons of the birds’ genomes with those of other animals pointed researchers towards a host of genes involved with the emergence of coloured feathers. While feathers may first have emerged for warmth, colourful plumage may have played a part in mating success. Researchers at the University of South Carolina found that waterbirds had the lowest number of genes linked to feather coloration, while domesticated pets and agricultural birds had eight times as many.

Further analysis of the genomes revealed that the common ancestor of all living birds lost its teeth more than 100m years ago. Mutations in at least six key genes meant that the enamel coating of teeth failed to form around 116m years ago. Tooth loss probably began at the front of the jaw and moved to the rear as the beak developed more fully.

“Ever since the discovery of the fossil bird Archaeopteryx in 1861, it has been clear that living birds are descended from toothed dinosaurs. However, the history of tooth loss in the ancestry of modern birds has remained elusive for more than 150 years,” said Mark Springer at the University of California, Riverside.

Birdsong has evolved more than once. Despite sharing many of the same genes, parrots and songbirds gained the ability to learn and copy sounds independently from hummingbirds. More striking is that the group of 50 or so genes that allow some birds to sing is similar to those that give humans the ability to speak. “This means that vocal learning birds and humans are more similar to each other for these genes in song and speech areas in the brain than other birds and primates are to them,” said Erich Jarvis at Duke University in North Carolina.

The common genes are involved in making fresh connections between brain cells in the motor cortex and those that control muscles used to make sounds.

The common genes are involved in making fresh connections between brain cells in the motor cortex and those that control muscles used to make sounds.

This video is called Penguin Fail – Best Bloopers from Penguins Spy in the Huddle (Waddle all the Way).

Penguins must withstand the cold and go without food for months on end, making fat storage a crucial factor in survival. The Adélie penguin were seen to have eight genes involved with metabolism of fatty lipids, though the emperor had only three.

The birds lost their ability to fly but their wings became supremely adapted to underwater acrobatics. Writing in the journal GigaScience, Li’s team describes 17 genes that have driven the re-shaping of penguins’ forelimbs. Mutations in one of those genes, called EVC2, causes Ellis-van Creveld syndrome, a genetic disorder that causes short-limb dwarfism and short ribs in people.

The first penguins evolved about 60m years ago, but the emperors and Adélies have markedly different histories. The Adélie penguin population grew rapidly 150,000 years ago as the climate warmed, but crashed by 40% when a cold and dry glacial period arrived 60,000 years ago.

The emperor penguins fared better, their numbers hardly changing, pointing to a better ability to handle the harsh environment.

Huge genetic analysis of 48 bird species confirms ‘big bang’ in bird diversity after dinosaurs went extinct: here.

The genomes of modern birds reveal how they emerged and evolved after the mass extinction that wiped out dinosaurs 66 million years ago, reports Smithsonian Science: here.

How some snakes became venomous, new research


This video is called The Evolution of Venom – Who is The Most Poisonous? [Full Documentary]

From the University of Texas at Arlington in the USA today:

Team proposes new model for snake venom evolution

17 hours ago

Technology that can map out the genes at work in a snake or lizard‘s mouth has, in many cases, changed the way scientists define an animal as venomous. If oral glands show expression of some of the 20 gene families associated with “venom toxins,” that species gets the venomous label.

But, a new study from The University of Texas at Arlington challenges that practice, while also developing a new model for how snake venoms came to be. The work, which is being published in the journal Molecular Biology and Evolution, is based on a painstaking analysis comparing groups of related genes or “gene families” in tissue from different parts of the Burmese python, or Python molurus bivittatus.

A team led by assistant professor of biology Todd Castoe and including researchers from Colorado and the United Kingdom found similar levels of these so-called toxic gene families in python oral glands and in tissue from the python brain, liver, stomach and several other organs. Scientists say those findings demonstrate much about the functions of genes before they evolved into venoms. It also shows that just the expression of genes related to venom toxins in oral glands of snakes and lizards isn’t enough information to close the book on whether something is venomous.

“Research on venom is widespread because of its obvious importance to treating and understanding snakebite, as well as the potential of venoms to be used as drugs, but, up until now, everything was focused in the , where venom is produced before it is injected,” Castoe said. “There was no examination of what’s happening in other parts of the snake’s body. This is the first study to have used the genome to look at the rest of that picture.”

Learning more about venom evolution could help scientists develop better anti-venoms and contribute to knowledge about gene evolution in humans.

Castoe said that with an uptick in genetic analysis capabilities, scientists are finding more evidence for a long-held theory. That theory says highly toxic venom proteins were evolutionarily “born” from non-toxic genes, which have other ordinary jobs around the body, such as regulation of cellular functions or digestion of food.

“These results demonstrate that genes or transcripts which were previously interpreted as ‘toxin genes’ are instead most likely housekeeping genes, involved in the more mundane maintenance of normal metabolism of many tissues,” said Stephen Mackessy, a co-author on the study and biology professor at the University of Northern Colorado. “Our results also suggest that instead of a single ancient origin, venom and venom-delivery systems most likely evolved independently in several distinct lineages of reptiles.”

Castoe was lead author on a 2013 study that mapped the genome of the Burmese python. Pythons are not considered venomous even though they have some of the same genes that have evolved into very toxic venoms in other species. The difference is, in highly venomous snakes, such as rattlesnakes or cobras, the venom gene families have expanded to make many copies of those shared genes, and some of these copies have evolved into genes that produce highly toxic venom proteins.

“The non-venomous python diverged from the snake evolutionary tree prior to this massive expansion and re-working of venom gene families. Therefore, the python represents a window into what a snake looked like before venom evolved,” Castoe said. “Studying it helps to paint a picture of how these gene families present in many vertebrates, including humans, evolved into deadly toxin encoding genes.”

Jacobo Reyes-Velasco, a graduate student from Castoe’s lab, is lead author on the new paper. In addition to Castoe and Mackessy, other co-authors are: Daren Card, Audra Andrew, Kyle Shaney, Richard Adams and Drew Schield, all from the UT Arlington Department of Biology; and Nicholas Casewell, of the Liverpool School of Tropical Medicine.

The paper is titled “Expression of Venom Gene Homologs in Diverse Python Tissues Suggests a New Model for the Evolution of Snake Venom.” It is available online here.

The research team looked at 24 gene families that are shared by pythons, cobras, rattlesnakes and Gila monsters, and associated with venom. The traditional view of venom evolution has been that a core venom system developed at one point in the evolution of snakes and lizards, referred to as the Toxicofera, and that the evolution of highly venomous snakes, known as caenophidian snakes, came afterward. But little explanation has been given for why evolution picked just 24 genes to make into highly toxic venom-encoding genes, from the 25,000 or so possible.

“We believe that this work will provide an important baseline for future studies by venom researchers to better understand the processes that resulted in the mixture of toxic molecules that we observe in venom, and to define which molecules are of greatest importance for killing prey and causing pathology in human snakebite victims,” Casewell said.

When they looked at the python, the team found several common characteristics among the venom-related gene families that differed from other genes. Compared with other python gene families, venom are “expressed at lower levels overall, expressed at moderate-high levels in fewer tissues and show among the highest variation in expression level across tissues,” Castoe said.

“Evolution seems to have chosen what genes to evolve into venoms based on where they were expressed (or turned on), and at what levels they were expressed,” Castoe said.

Based on their data, the new paper presents a model with three steps for venom evolution. First, these potentially venomous genes end up in the oral gland by default, because they are expressed in low but consistent ways throughout the body. Then, because of natural selection on this expression in the oral gland being beneficial, tissues in the mouth begin expressing those genes in higher levels than in other parts of the body. Finally, as the venom evolves to become more toxic, the expression of those genes in other organs is decreased to limit potentially harmful effects of secreting such toxins in other body tissues.

The team calls its new model the Stepwise Intermediate Nearly Neutral Evolutionary Recruitment, or SINNER, model. They say differing venom levels in snakes and other animals could be traced to the variability of where different species, or different genes within a species, are along the continuum between the beginning and end of the SINNER model.

Castoe said the next step in the research would be to examine the genome of highly venomous snakes to see if the SINNER model bears out. For now, he and the rest of the team hope that their findings about the presence of venom-related in other parts of the python change some thinking on what species are labeled as venomous.

“What is a venom and what species are venomous will take a lot more evidence to convince people now,” Castoe said. “It provides a brand new perspective on what we should think of when we look at those oral glands.”

Human evolution, alcohol and chemistry


This video is called African Animals Getting Drunk From Ripe Marula Fruit.

By Bob Yirka today:

Study shows pre-human ancestors adapted to metabolize ethanol long before humans learned about fermentation

19 hours ago

(Phys.org)—A team of researchers in the U.S. has found evidence to support the notion that our pre-human ancestors were able to metabolize ethanol long before our later ancestors learned to take advantage of fermentation—to create alcoholic beverages. In their paper published in Proceedings of the National Academy of Sciences, the team describes how they genetically sequenced proteins from modern primates and used what they found to work backwards to discover just how long ago our ancestors have been able to metabolize ethanol.

Humans have been consuming beverages that make them tipsy, drunk and/or sick for a very long time, of that there is little doubt. But why do we have the ability to metabolize ethanol in the first place? That’s what the team set out to answer. They began by sequencing an enzyme called ADH4—it’s what’s responsible for allowing us to metabolize ethanol. Other have it as well, but not all metabolize ethanol as well as we do. By sequencing ADH4 found in a 28 including 17 that were primates, the team was able to create a family tree of sorts based on ethanol metabolizing ability. The team then tested those sequences for their metabolizing ability by synthesizing nine kinds of the ADH4 enzyme. Doing so showed the researchers that most early primates had very little ability to metabolize ethanol for most of their early history.

Then, about 10 million years ago, some of the ancestors of modern humans suddenly were able to do a much better job of it, while others that diverged and led to apes such as orangutans, did not. This discovery led the team to wonder what might have occurred to cause this to come about. They note that other evidence has shown that around this same time, the planet cooled slightly, making life a little more difficult for our tree dwelling ancestors. They suggest they began climbing down out of the trees to eat the fruit that fell, which gave them a food advantage and a reason for developing the ability to metabolize —otherwise they would have become too drunk from eating the fermenting fruit to defend themselves or live otherwise normal lives. If true, the theory would also offer a major clue as to why our became terrestrial.

Explore further: Study unlocks secret of how fruit flies choose fruit with just the right amount of ethanol

More information: Hominids adapted to metabolize ethanol long before human-directed fermentation, PNAS, Matthew A. Carrigan, DOI: 10.1073/pnas.1404167111

Abstract

Paleogenetics is an emerging field that resurrects ancestral proteins from now-extinct organisms to test, in the laboratory, models of protein function based on natural history and Darwinian evolution. Here, we resurrect digestive alcohol dehydrogenases (ADH4) from our primate ancestors to explore the history of primate–ethanol interactions. The evolving catalytic properties of these resurrected enzymes show that our ape ancestors gained a digestive dehydrogenase enzyme capable of metabolizing ethanol near the time that they began using the forest floor, about 10 million y ago. The ADH4 enzyme in our more ancient and arboreal ancestors did not efficiently oxidize ethanol. This change suggests that exposure to dietary sources of ethanol increased in hominids during the early stages of our adaptation to a terrestrial lifestyle. Because fruit collected from the forest floor is expected to contain higher concentrations of fermenting yeast and ethanol than similar fruits hanging on trees, this transition may also be the first time our ancestors were exposed to (and adapted to) substantial amounts of dietary ethanol.

Birds, dinosaurs, eggs and evolution


This video is called Hundreds of Dinosaur Egg Fossils Found in Spain.

From Wildlife Extra:

Egg shapes could be key to explaining evolution of birds

Research by scientists suggests that bird egg shape could be key in explaining their evolution

Next time you sit down to your breakfast of hard-boiled egg, you might want to take a moment to stop to consider why it is so perfectly ‘egg-shaped’. Evolutionary biologists have been studied [sic] the difference in the eggs of modern day birds compared to those of their extinct relatives, Theropod dinosaurs. The difference in their shape could be the key to explaining why some birds were able to survive the extinction event that wiped out the dinosaurs.

Researchers from University of Lincoln examined eggshells looking at the transition of Theropods into birds based on fossil records and studies of modern birds.

Their findings suggest that the early birds from 252 to 66 million years ago laid eggs that had different shapes to those of modern birds. This might suggest that embryonic development was different in the earliest birds, so could have implications for how some birds survived while the dinosaurs perished.

The author of the study was Dr Charles Deeming of Lincoln’s School of Life Sciences. He explains, “These results indicate that egg shape can be used to distinguish between different types of egg-laying vertebrates. More importantly they suggest Mesozoic bird eggs differ significantly from modern day bird eggs, but more recently extinct Cenozoic birds do not. This suggests that the range of egg shapes in modern birds had already been attained in the Cenozoic.”

The origin of the amniotic egg, which is an egg that can survive out of water, is one of the key adaptions underpinning the vertebrates’ transition from sea to land over 300 million years ago.

Dr Deeming suggests that the different egg shape of birds both past and present could be associated with different nesting behaviours or incubation methods, but points out that not much research has been carried out into this due to insufficient fossil data. “We hope that future discoveries of associated fossil eggs and skeletons will help refine the general conclusions of this work,” he says.

Florida green anoles adapt to invasive species


This video from the USA says about itself:

The largest Green Anole ever!

The Carolina anole (Anolis carolinensis) is an arboreal lizard found primarily in the southeastern United States and some Caribbean islands. Other common names include the green anole, American anole and red-throated anole. It is also sometimes referred to as the American chameleon due to its ability to change color from several brown hues to bright green. While many kinds of lizards are capable of changing color, anoles are closely related to iguanas and are not true chameleons. The Carolina is a small lizard; male adults are usually 15 cm (5.9 in) long in adulthood, about half of which is its tail, and it can weigh from 3–7 g (0.11–0.25 oz). Exceptionally, these anoles will grow up to 20 cm (7.9 in) in length.

From Breaking News:

A lizard species in Florida has evolved very quickly to deal with invaders

24/10/2014 – 12:16:32

In as little as 15 years, lizards native to Florida – known as Carolina anoles or green anoles – have adapted to deal with the threat of an invading species of lizard, Cuban or brown anoles.

This video is called Egg-laying brown anole (Anolis sagrei), Aruba. This female brown anole was filmed during digging a hole in the sand in which she layed an egg.

After having contact with the invasive species, said to have first gone to America from Cuba in the 1950s, the native lizards starting perching higher up in trees. Over the course of 15 years and 20 generations, their feet evolved to become better at gripping the thinner, smoother branches found higher up.

The change was rapid. After a few months the native lizards started moving higher up the branches and over 15 years, their toe pads had become larger with stickier scales on their feet.

“We did predict that we’d see a change, but the degree and quickness with which they evolved was surprising,” said Yoel Stuart, a post-doctoral researcher in the College of Natural Sciences at The University of Texas at Austin and lead author of the study.

“To put this shift in perspective, if human height were evolving as fast as these lizards’ toes, the height of an average American man would increase from about 5 foot 9 inches today to about 6 foot 4 inches within 20 generations — an increase that would make the average U.S. male the height of an NBA shooting guard,” said Stuart. “Although humans live longer than lizards, this rate of change would still be rapid in evolutionary terms.”

This latest study is one of only a few well-documented examples of what evolutionary biologists call “character displacement,” where similar species competing with each other evolve differences to take advantage of different ecological niches.

A classic example comes from the finches studied by Charles Darwin. Two species of finch in the Galapagos Islands diverged in beak shape as they adapted to different food sources.

The researchers speculate that the competition between brown and green anoles for the same food and space may be driving the adaptations of the green anoles. Stuart also noted that the adults of both species are known to eat the hatchlings of the other species.

“So it may be that if you’re a hatchling, you need to move up into the trees quickly or you’ll get eaten,” said Stuart. “Maybe if you have bigger toe pads, you’ll do that better than if you don’t.”

The research was published in the journal Science.

See also here. And here. And here.

Florida: Protecting a Home Where the Puffer Fish Roam in Biscayne National Park: here.

Venezuelan opossums and the origin of species


This video, in Spanish, from Venezuela about a mouse opossum is called Marmosa robinsoni.

From Wildlife Extra:

New study could change the traditional view of how species come about

A team of researchers from the City University of New York working on the Península de Paraguaná in Venezuela have made a discovery that could revolutionise our understanding of how the origin of a new species takes place.

Up to now it has been accepted that the primary drivers in a species becoming isolated, and consequently developing sufficiently separate characteristics to become genetically distinct, are physical in nature – the uplift of mountains, the formation of islands, the change in the course of a river, creating barriers.

The findings of the study of two species of mouse opossums, Marmosa xerophila and Marmosa robinsoni, have now added interactions among species as another way that populations can become geographically isolated, which could promote the formation of new species.

In their paper the authors, Eliécer E Gutiérrez, Robert A Boria and Robert P Anderson, say that these interactions might include, ‘the presence of particularly effective predators or strong competitors, or the absence of important prey or essential mutualistic species.’

This new theory has come about as a result of observations on the Paraguaná peninsula, which is separated from the mainland only by a spit of sand, in which the researchers found that M. robinsoni has become separated from populations of the same species found on the mainland, not because the habitat in between is unsuitable, but because it is mostly occupied by M. xerophila.

The inability of individuals of that population of M. robinsoni to mate with individuals of mainland populations could, in time, lead to their genetic differentiation and the origin of a new species.

To read more about the study go to www.ecography.org/content/august-2014.