New study reveals how metamorphosis has shaped the evolution of salamanders

JUNE 23, 2020

by Natural History Museum

A team of scientists, led by Natural History Museum postdoctoral researcher Dr. Anne-Claire Fabre, have conducted the first study on how metamorphosis has influenced the evolution of salamanders.

Using micro-CT scanning to study the skulls of this group of animals, the team were able to build a huge dataset of 148 species of salamanders and used cutting-edge methods to describe the shape of the skull with nearly 1000 reference points, known as landmarks.

Dr. Fabre said, "Most studies of this kind are limited to just a few dozen landmarks. Our study is the first large-scale investigation of this incredibly diverse group. We have captured the shape of the skull in such great detail that it has allowed us to learn more than ever before about how these creatures evolved."

The results showed that the ancestor of all salamanders was metamorphic but that different life cycles have evolved at least 11 times across the group. Even more interesting, when different life cycles evolve, salamanders show a burst of rapid evolution, showing that shifts in life cycle promoted the evolution of new forms and increased their diversity.

Prof. Anjali Goswami, a research leader at the Natural History Museum, who is the senior author of the study, said, "We can see that metamorphosis has profoundly influenced salamander evolution, allowing for more independent evolution of the parts of the skull related to feeding and ultimately resulting in a greater diversity of skull shapes. This means that metamorphosis, and repeated changes from metamorphosis to other life cycles like live birth or losing the larval or adult stage entirely, have been key drivers of the diversity of salamanders over the past 180 million years."

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Ancient fish fossil reveals evolutionary origin of the human hand

18th March 2020

by Flinders University

An ancient Elpistostege fish fossil found in Miguasha, Canada has revealed new insights into how the human hand evolved from fish fins.

An international team of palaeontologists from Flinders University in Australia and Universite du Quebec a Rimouski in Canada have revealed the fish specimen, as described in the journal Nature, has yielded the missing evolutionary link in the fish to tetrapod transition, as fish began to foray in habitats such as shallow water and land during the Late Devonian period millions of years ago.

This complete 1.57 metre long fish shows the complete arm (pectoral fin) skeleton for the first time in any elpistostegalian fish. Using high energy CT-scans, the skeleton of the pectoral fin revealed the presence of a humerus (arm), radius and ulna (forearm), rows of carpus (wrist) and phalanges organized in digits (fingers).

"Today we announce in the journal Nature our discovery of a complete specimen of a tetrapod-like fish, called Elpistostege, which reveals extraordinary new information about the evolution of the vertebrate hand," says Strategic Professor in Palaeontology at Flinders University Professor John Long.

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They were once domestic pets, then natural selection made dingoes wild

FEBRUARY 11, 2020

by KTH Royal Institute of Technology

Believed to have been pets at one stage in their evolution, the origins of the Australian dingo are shrouded in mystery, compelling generations of biologists to snoop for clues about their early history. New evidence has recently been revealed by a genomic study that offers tantalizing details about their adaptation from domesticated to wild animals.

The study's lead author Peter Savolainen, professor at the Department of Gene Technology at KTH Royal Institute of Technology, says that thousands of years ago these outback predators were pet dogs in Asia. According to the genetic analyses, dingoes began their journey of feralization—and their migration to Australia—8,300 years ago when they split off from their ancestors, which today are known as Indonesian village dogs.

"Our analyses of phylogeny, population structure, and demography as well as selection analysis, show that the dingo is a genetically distinct population clearly differentiated from the domestic dog," Savolainen says. "Genes related to behaviour, food digestion and reproduction have evolved in order to adapt dingoes to living in the wild instead of together with humans."

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Secrets of the largest ape that ever lived

By Helen Briggs

13 November 2019

A fossilised tooth left behind by the largest ape that ever lived is shedding new light on the evolution of apes.

Gigantopithecus blacki was thought to stand nearly three metres tall and tip the scales at 600kg.

In an astonishing advance, scientists have obtained molecular evidence from a two-million-year-old fossil molar tooth found in a Chinese cave.

The mystery ape is a distant relative of orangutans, sharing a common ancestor around 12 million years ago.

"It would have been a distant cousin (of orangutans), in the sense that its closest living relatives are orangutans, compared to other living great apes such as gorillas or chimpanzees or us," said Dr Frido Welker, from the University of Copenhagen.

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How gliding animals fine-tuned the rules of evolution

SEPTEMBER 23, 2019

by Lachlan Gilbert, University of New South Wales

A study of gliding animals has challenged the idea that evolutionary innovations—adaptations that bring new abilities and advantages—spur the origin of other new body types and other characteristics in descendant species.

The research, undertaken by evolutionary biologists at UNSW Sydney and universities in the US and Spain, examined the key innovation of gliding in two types of gliding animals: 'flying' dragons (family Agamidae) and 'flying' squirrels (family Sciuridae), both common to forests in South East Asia.

The study confirms previous assumptions that gliding animals originated from arboreal ancestors and likely arose as a means of escaping predators some 25-30 million years ago.

Lead author Dr. Terry Ord, an evolutionary ecologist with UNSW's Evolution & Ecology Research Centre, says another advantage that gliding brought was the ability to exploit a new three dimensional environment and explore more of the forest than just one tree.

"From an evolutionary biologist's perspective, these types of innovation that open up new opportunities are assumed to drive even more adapted diversification," Dr. Ord says.

"Suddenly there's all these new microhabitats available offering up new resources and you have new species moving into those particular microhabitats where you would expect them to adapt even more."

Winging it

The evolution of flight in birds, insects and bats is an example where the changes brought about by 'taking to the wing' caused an explosion in diversity. Millions of species of insects, tens of thousands of birds and more than a thousand species of bats developed greatly different shapes, sizes, behaviours and habitats since their ancestors first evolved to fly.

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Guppies teach us why evolution happens

Places, not predators, are evolution catalysts

Date: September 18, 2019

Source: University of California - Riverside

Guppies, a perennial pet store favorite, have helped a UC Riverside scientist unlock a key question about evolution:

Do animals evolve in response to the risk of being eaten, or to the environment that they create in the absence of predators? Turns out, it's the latter.

David Reznick, a professor of biology at UC Riverside, explained that in the wild, guppies can migrate over waterfalls and rapids to places where most predators can't follow them. Once they arrive in safer terrain, Reznick's previous research shows they evolve rapidly, becoming genetically distinct from their ancestors.

"We already knew that they evolved quickly, but what we didn't yet understand was why," Reznick said. In a new paper published in American Naturalist, Reznick and his co-authors explain the reason the tiny fish evolve so quickly in safer waters.

To answer their questions, the scientists traveled to Trinidad, guppies' native habitat, and conducted an experiment. They moved guppies from areas in streams where predators were plentiful to areas where predators were mostly absent. Over the course of four years, they studied how the introduced guppies changed in comparison to ones from where they originated.

"If guppies evolve because they aren't at risk of becoming food for other fish, then evolution should be visible right away," Reznick said. "However, if in the absence of predators they become abundant and deplete the environment of food, then there will be a lag in detectable changes."

Guppies from all four streams were marked so they could be tracked over the course of four years. The scientists tracked the males, which tend to live about five months. They looked at the fishes' age and size at maturity, which are key traits affecting population growth.

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Why Haven't All Primates Evolved into Humans?

By Grant Currin, Live Science Contributor | July 14, 2019 09:38am ET

While we were migrating around the globe, inventing agriculture and visiting the moon, chimpanzees — our closest living relatives — stayed in the trees, where they ate fruit and hunted monkeys.

Modern chimps have been around for longer than modern humans have (less than 1 million years compared to 300,000 for Homo sapiens, according to the most recent estimates), but we've been on separate evolutionary paths for 6 million or 7 million years. If we think of chimps as our cousins, our last common ancestor is like a great, great grandmother with only two living descendants.

But why did one of her evolutionary offspring go on to accomplish so much more than the other? [Chimps vs. Humans: How Are We Different?] 

"The reason other primates aren't evolving into humans is that they're doing just fine," Briana Pobiner, a paleoanthropologist at the Smithsonian Institute in Washington, D.C., told Live Science. All primates alive today, including mountain gorillas in Uganda, howler monkeys in the Americas, and lemurs in Madagascar, have proven that they can thrive in their natural habitats.

"Evolution isn't a progression," said Lynne Isbell, a professor of anthropology at the University of California, Davis. "It's about how well organisms fit into their current environments." In the eyes of scientists who study evolution, humans aren't "more evolved" than other primates, and we certainly haven't won the so-called evolutionary game. While extreme adaptability lets humans manipulate very different environments to meet our needs, that ability isn't enough to put humans at the top of the evolutionary ladder.

Take, for instance, ants. "Ants are as or more successful than we are," Isbell told Live Science. "There are so many more ants in the world than humans, and they're well-adapted to where they're living."

While ants haven't developed writing (though they did invent agriculture long before we existed), they're enormously successful insects. They just aren't obviously excellent at all of the things humans tend to care about, which happens to be the things humans excel at.

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Study reveals new genomic roots of ecological adaptation in polar bear evolution

How natural selection shaped gene copy numbers

Date:  June 17, 2019

Source:  University of Massachusetts at Amherst

Scientists from the University of Massachusetts Amherst, Vanderbilt University and Clark University have shed new light on the genomic foundation of the polar bear's ecological adaption by pinpointing rapid changes in the bear's gene copy numbers in response to a diet shifting from vegetation to meat.

In a paper published Monday, June 17 in the Proceedings of the National Academy of Sciences and chosen for the cover of PNASVol. 116, issue 27, John G. Gibbons and Ph.D. student Shu Zhao of UMass Amherst, David C. Rinker of Vanderbilt and Natalya K. Specian of Clark discuss the first population-level study to characterize genome-wide patterns of copy number variation (CNV) in the polar bear and brown bear.

CNV refers to differences among individuals in the number of copies of a particular portion of the genome, and the study's results suggest this variation played an important role in the adaptation of polar bears to the Arctic.

"This research addresses a big-picture evolutionary question of how diet shapes the genome," explains Gibbons, assistant professor of food science.

Since the brown or grizzly bear (Ursus arctos) and polar bear (Ursus maritimus) diverged less than 500,000 years ago, the polar bear has evolved unique traits to adapt to the Arctic climate and ecology, such as a camouflaging coat of pigment-free fur. Previous population genomic studies of polar bears and brown bears analyzed single-nucleotide polymorphisms, or changes in a single base pair in a DNA sequence.

"CNVs were traditionally harder to detect so they weren't always analyzed," Gibbons says. "With recent advances in DNA sequencing technologies over the last 15 years or so, computational approaches to detect and quantify CNVs from genomic data have been developed. The polar bear data gave us a nice opportunity to fill in the gap."

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How new species arise in the sea

Study sheds new light on a fundamental question in evolutionary biology

Date:  March 4, 2019

Source:  Helmholtz Centre for Ocean Research Kiel (GEOMAR)

For a new species to evolve, two things are essential: a characteristic -- such as a colour -- unique to one species and a mating preference for this characteristic. For example, individuals from a blue fish species prefer blue mates and individuals from a red fish species prefer red mates. If the two species interbreed, the process of sexual recombination is expected to destroy the coupling between colour and mate preferences and form red individuals with a preference for blue mates and vice versa. This will prevent the two species from diverging, and this is one of the reasons why it has been thought for a long time that new species can only evolve in absolute isolation, without interbreeding.

However, the dynamics of this process depend on the exact number and location of genes underlying species characteristics and mate preferences, the strength of natural selection acting on these genes, and the amount of interbreeding between species. In a new study, Professor Oscar Puebla from GEOMAR Helmholtz Centre for Ocean Research Kiel in Germany together with colleagues from the Smithsonian Tropical Research Institute in Panama have found that natural selection can couple the evolution of genes for colour pattern and mate preferences when species still interbreed. The study has been published today in the international journal Nature Ecology and Evolution.

"To address this question, the first challenge was to identify an animal group in which species are still young and interbreed, with clear species characteristics, and in which the bases of reproductive isolation are well understood," Oscar Puebla explains. The hamlets, a group of closely related reef fishes from the wider Caribbean, constitute exactly such a group. The hamlets are extremely close genetically, differ essentially in terms of colour pattern, and are reproductively isolated through strong visually-based mate preferences.

Read more

Sloths: how did two different animals wind up looking so similar?

March 12, 2019 by Richard Gray, From Horizon Magazine, Horizon: The EU Research & Innovation Magazine

Sloths and guppies appear to have little in common – one is an arboreal mammal living in the slow lane, while the other is a tiny tropical fish with a frantic existence. Yet both could hold the key to better understanding a fundamental process of evolution.

Hanging lazily from tree branches where they barely move for hours on end, sloths hardly seem like born survivors. Yet the sloths that creep through the rainforest canopies of Central and South America are the last remaining members of a group of animals that has roamed the Earth for at least 30 million years and once boasted hundreds of species.

Many of their extinct cousins were giants – some larger than elephants – that spent most of their time on the ground before they died out 10,000 years ago at the end of the last ice age. Modern sloths, however, are thought to have avoided the extinctions that wiped out their larger relatives because they ascended into the trees.

But what makes their survival more extraordinary is that the two types of modern sloths – the two-toed and the three-toed sloths – are thought to have adapted to life in the trees entirely independently of each other. They are an example of what is known in biology as convergent evolution – a process where species develop similar adaptations to a habitat through different evolutionary routes.

"When you look at them hanging in the trees, the two look very similar," said Dr. Marcela Uliano da Silva, a computational biologist at the Leibniz Institute for Zoo and Wildlife Research in Berlin, Germany.

'(But) they have different numbers of toes on their forelimbs and the way the muscles connect from the body to the bones in the arms is also different," she said.

Evolutionary tree

These physical differences are signs that two-toed and three-toed sloths found their own ways to adapt to a lifestyle in the trees. They are thought to have last shared a common ground-dwelling ancestor about 30 million years ago, which is around the same time that humans split from baboons on the evolutionary tree.

In most cases, evolution tends to follow a classic route where species diversify from a common ancestor to adapt to different habitats and challenges. Modern sloths, however, are an example of where evolution has gone in the opposite direction by separately adapting to have very similar lives in the trees.

Read more at: 

Some worms recently evolved the ability to regrow a complete head

Date:  March 6, 2019

Source:  University of Maryland

An international group of researchers including biologists from the University of Maryland found that at least four species of marine ribbon worms independently evolved the ability to regrow a head after amputation.

Regeneration of amputated body parts is uncommon but does exist throughout the animal world -- from salamanders, spiders and sea stars that can regrow appendages to a species of ribbon worm that can regenerate an entire individual from just a small sliver of tissue. But regenerative abilities were broadly assumed to be an ancient trait that some species managed to hold on to while most others lost through evolution.

This new study, which was published in the March 6, 2019 issue of Proceedings of the Royal Society B, turns that assumption on its head. In a survey of 35 species of marine ribbon worms, the researchers found that the ability to regenerate an entire head, including a brain, evolved relatively recently in four different species.

"This means that when we compare animal groups we cannot assume that similarities in their ability to regenerate are old and reflect shared ancestry," said Alexandra Bely, associate professor of biology at UMD and one of the study's authors. "We need to be more careful when comparing regeneration findings across different groups of animals."

All animals have some degree of regenerative ability. Even humans re-grow damaged skin over a wound. However, animal lineages that diverged very early in evolutionary history -- such as sponges, hydroids and ctenophores -- are often able to regrow entire individuals from even small amputated parts. As animals evolved greater complexity, regenerative abilities have become less dramatic and common.

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South American lizards are breaking an evolutionary 'golden rule' – via Herp Digest

By Erin Handley 2/14/19 , Australian Broadcasting Network

Damien Esquerre has been fascinated by lizards since he was a child.

Key points:

Egg-laying lizards appear to have gone from eggs to birthing live young and back again

It's a transition that's believed to be extremely rare

South America's Andes mountains are 'sky islands' and hotbeds for biodiversity

Now the Chilean-born researcher has made a groundbreaking — but controversial — discovery about the scaly critters, one that challenges a fundamental rule of evolution.

He found egg-laying lizards propelled to the cold Andean mountaintops in South America had evolved to give birth to live young.

But in a remarkable backflip, a handful of the species appears to have returned to an egg-laying state when moved back down the mountain to warmer areas.

"Eggs do not incubate very well at cold temperatures, and of course the mountaintops in the Andes are pretty cold. Laying eggs wouldn't work in that kind of environment, so they had to evolve giving birth to live young," Mr Esquerre said.

"We have strong evidence that suggests that they re-evolved laying eggs when they re-colonised warmer areas.”

"No mammal has ever re-evolved egg laying, but these lizards seem to.”

This switch from eggs to live young and back again marks an evolutionary transition believed to be extremely rare, Mr Esquerre said in recent paper for peer-reviewed journal Evolution.

He said Dollo's Law of irreversibility states that once a species loses a trait through evolution, it's extremely unlikely to regain it.

"For example, snakes lost their limbs, so re-evolving limbs is very unlikely or impossible … Laying eggs is one of the classic examples of Dollo's Law," he said.

Louis Dollo first proposed the principle in 1983.

Since then, it's been widely accepted — Australian National University calls it a "golden rule" of biology — though there are numerous exceptions.

Some studies have noted that certain sand boas and vipers, for example, have re-evolved egg laying.

But his research comes with a caveat: more study is needed.

"We think it's significant and slightly controversial. We think a lot of scientists are going to — with reason — be very sceptical," he said.

"We can never be 100 per cent certain about this.

"This opens a window to start looking into this with more detail. It would be a very significant evolutionary event if true, and we have some evidence that it actually happens."

'Sky islands' fuelling biodiversity

The group of lizards featured in Mr Esquerre's study are considered one of the most diverse in the world, comprising 260 species. Around half give birth to live young, while the other half lay eggs.

Between three and eight of those species could have reverted back to egg laying after evolving to birth live young, he said.

The lizards are highly adaptable — they can be found at the southern tip of South America, close to the Antarctic, and also in the Atacama desert, one of the direst places on earth.

Some lizards have brown, subdued hues to blend next to rocky terrains, while those that live in the rainforest sport bright green and blue tones.

"We tried to date the origin of this group and we found that it has roughly the same age as the Andes — 20 million years — which is actually really, really young in terms of geology and evolution," Mr Esquerre said.

To get a grasp on the timeline, he pointed out that dinosaurs went extinct 65 million years ago.

"The Andes are formed by the collision of two tectonic plates, and when they collide they are smushing each other upwards, so they form mountain chains. As they were being uplifted, the number of species in this group increased. How do we explain that?

"The best way to explain it is thinking of mountains as islands. As mountaintops rose, different populations of these lizards were getting trapped — just like if a group of islands gets divided, the populations of animals will be divided and isolated from each other.

"New species form when you have isolation plus time … if two populations are separated, given enough time they're going to become two entirely different species.”

To reconstruct evolution at this scale, Mr Esquerre and his team worked on making a family tree of the species by sequencing and comparing DNA, to see which lizards shared similarities and which were more distantly related.

Natural selection played a large part in the findings, he said.

"The ones who lay eggs quickly will start to die off and be selected out, whereas the ones who that retain their eggs for longer and incubate it in their uterus for longer will have higher chances of survival," he said.

"Just by slowly selecting that egg retention strategy, you'll eventually end up with females that don't even lay eggs — they just incubate their eggs inside and hatch inside.

"Given more and more and more time and natural selection, you'd end up with a completely live-bearing species.”

Scientific scepticism

But Dr Oliver Griffith, an evolutionary biologist at the University of Melbourne who specialises in pregnancy in lizards, urged caution about the findings.

"We really need those next experiments before we can make any strong claims," he said.

"I think their model doesn't consider the difficulty of going from being a live bearing animal to an egg laying one.”

Dr Griffith said while scientists had a good understanding about how animals changed from egg-laying to live bearing, "we don't have any evidence at all of how it might go in the opposite direction".

But he liked the study's examination of the impacts of climate on these wildly varied lizards.

"I think they've done a really good job of looking at how climate might drive the evolution of pregnancy in this group of lizards," he said.

He added that Dollo's Law was not meant to be a hard and fast rule, but "basically it's that you can't go back in time in evolution". While it may be possible to return to a certain state, "you can't really go back in the same way that you got there in the first place," by retracing footsteps, he said.

"So if you find a way to climb up a building, then you're not going to climb down the building the same way that you got up there — you might slide down a pole, rather than find individual bricks.”

He said the study primarily focused on studying the historical relationships of lineages of species, but there needed to be more work on the physiological side of things — the internal machinery of laying eggs —something Mr Esquerre also noted in his paper.

"The crux is, can we get some of these other types of evidence to show this actually has occurred?" Dr Griffith said.

"If we really want to believe a theory, then we need to get as many different kinds of evidence for that theory that we can.”

Piece to the puzzle of baleen whales' evolution

Date:  January 22, 2019

Source:  University of Otago

An Otago researcher has added another piece to the puzzle of the evolution of modern baleen whales with a world-first study examining the teeth and enamel of baleen whales' ancestors.

Modern baleen whales have no teeth when adults, instead they use large keratin plates called baleen to filter prey from large volumes of seawater. However, millions of years ago their ancestors had teeth as most mammals do.

Lead author of the research just published in the Journal of Mammalian Evolution, Dr Carolina Loch from the Faculty of Dentistry, explains scientists are still trying to understand how and why this process happened. The research she carried out together with colleagues from the National Scientific and Technical Research Council in Argentina, CONICET, and the Swedish Museum of Natural History has provided more information.

They studied details of the inside structure of the teeth of two fossil whales from around 35 million years ago. These teeth were collected in Antarctica by the Argentinian and Swedish study co-authors Monica Buono and Thomas Mörs. Because teeth are naturally heavily mineralised, they preserve well in the fossil record and can provide clues of how extinct animals lived.

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Howler monkey study examines mechanisms of new species formation

December 22, 2018, University of Michigan

A new University of Michigan study of interbreeding between two species of howler monkeys in Mexico is yielding insights into the forces that drive the evolution of new species.

How do new species emerge in nature? One common but overly simplified version of the story goes like this: A population of animals or plants becomes geographically isolated—by a river that changes course or a mountain range that rises up, for example—and the two separated groups accumulate genetic differences over time as they adapt to their environments in isolation.

Eventually, the DNA of the two groups is so different that the two populations are considered distinct species. Voilà, speciation has occurred.

In reality, the process is much more complex than that. While geographic isolation can start the speciation process, evolutionary biologists believe that other forces—including various forms of natural selection—can help to complete it.

The new U-M study provides rare empirical evidence that multiple forms of natural selection, including a contentious one called reinforcement, are helping to complete the speciation process in a natural howler monkey "hybrid zone," a place where the two species coexist and occasionally interbreed in a process called hybridization.

The study is scheduled for online publication Dec. 22 in the journal Molecular Ecology. In the paper, the researchers use the primate hybrid zone to identify parts of the genome that are likely to contain genes underlying speciation and to test for signals of the selection forces that shaped them.

"We observed patterns in the genetic data suggesting that hybridization is playing a direct role in completing the speciation process by enhancing genetic differences between species," said U-M doctoral candidate Marcella Baiz, the study's first author. The other authors are Liliana Cortés-Ortiz and Priscilla Tucker of the U-M Department of Ecology and Evolutionary Biology.

"We found a signal for multiple forms of natural selection driving species differences, including reinforcement, a process that has been highly debated," Baiz said. "This result is particularly notable because empirical evidence for reinforcement is extremely rare, especially genetic evidence."

Read more at: 

Species at the extremes of the food chain evolve faster, study says

December 17, 2018, University of Tennessee at Knoxville

Reef fish species at the extremes of the food chain—those that are strict herbivores or strict fish predators—evolve faster than fish species in the middle of the food chain with a more varied diet, according to a new study published in Nature Ecology and Evolution.

The paper, co-authored by Samuel Borstein, a Ph.D. candidate in the Department of Ecology and Evolutionary Biology, could challenge the way scientists think about evolution in relation to the position a species holds on the food chain.

Up until now, scientists thought that species that eat a wide variety of different foods might evolve quicker and show more variations in morphology—physical aspects such as size, shape, and color.

However, Borstein and his team were able to prove the exact opposite: species with the most limited diet are evolving faster.

For the study, the researchers produced an evolutionary "family tree" that describes the relationships of more than 1,500 coral reef species, their place in the food chain, and the diversity of items on which they feed.

They also digitized hundreds of photographs of reef fish to gather information on physical traits that are important for feeding, such as the depth of the peduncle (the part of the fish where body and fins attach).

Read more at: 

Primates of the Caribbean: Ancient DNA reveals history of mystery monkey

Weird evolution revealed in now-extinct monkey which inhabited Jamaica until a few hundred years ago

Date:  November 12, 2018

Source:  Zoological Society of London

Analysis of ancient DNA of a mysterious extinct monkey named Xenothrix -- which displays bizarre body characteristics very different to any living monkey -- has revealed that it was in fact most closely related to South America's titi monkeys (Callicebinae). Having made their way overwater to Jamaica, probably on floating vegetation, their bones reveal they subsequently underwent remarkable evolutionary change.

The research published today in Proceedings of the National Academy of Sciences (12 November 2018) and carried out by a team of experts from international conservation charity ZSL (Zoological Society of London), London's Natural History Museum (NHM), and the American Museum of Natural History in New York, also reveals that monkeys must have colonised the Caribbean islands more than once. The study reports an incredible discovery of how the unusual ecology of islands can dramatically influence animal evolution.

Xenothrix, unlike any other monkey in the world, was a slow-moving tree-dweller with relatively few teeth, and leg bones somewhat like a rodent's. Its unusual appearance has made it difficult for scientists to work out what it was related to and how it evolved. However, the scientific team have successfully extracted the first ever ancient DNA from an extinct Caribbean primate -- uncovered from bones excavated in a Jamaican cave and providing important new evolutionary insights.

Continued 

Tortoise evolution: How did they become so big?

Date: October 23, 2018

Source: Martin-Luther-Universität Halle-Wittenberg

Tortoises are a group of terrestrial turtles globally distributed in habitats ranging from deserts to forests and include species such as the Greek and the Galapagos tortoise. Some species evolved large body sizes with a shell length exceeding 1 metre whereas others are no larger than 6-8 centimetres. Despite a particular interest from naturalists ever since the times of Darwin, the evolution of gigantism in tortoises remains enigmatic.

The fact that all living giant tortoises are insular may suggest that their evolution followed the so-called island rule: a trend toward dwarfism of large animals and gigantism of small animals on islands. An example of insular dwarfism is the Florida key deer, a dwarf version of the mainland white-tailed deer; its small size may be an adaptation to the limited resources found on the islands. Insular gigantism is best exemplified by the famous dodo, an extinct flightless pigeon from Mauritius, probably evolving large body size due to release from predatory pressure. Previous studies on extant tortoises were partly inconclusive: giant size has been linked to the absence of predatory mammals in islands but it has been also proposed that tortoises were already giants when they reached the remote archipelagos. Since very few giant tortoise species survive to the present, these hypotheses are impossible to test without analysing extinct species through the help of the fossil record.

Continued

Getting a grip on the slow but unique evolution of sharks

Date:  October 8, 2018

Scientists at the RIKEN Center for Biosystems Dynamics Research (BDR) in Japan, in collaboration with other Japanese institutes and aquariums, have decoded the whole genomes of two shark species for the first time and improved the whale shark genome sequences released previously. By analyzing the genomes and comparing them with those of other vertebrate species, they have constructed an overview of their unique life histories and evolutionary paths. This work was published online in Nature Ecology and Evolution.

Advances in genome sequencing have made it possible to compare genomes from different species, giving us insights into their evolutionary histories and characteristics. While data for many organisms are available, to date, genome sequencing for sharks has been hampered by their huge genomes, which are even larger than the human genome. The notable exception is the elephant shark, although strictly speaking this fish is not professionally classified as a true shark.

Sharks have many unique characteristics, including their body structures, reproductive systems, way of sensing, and extreme longevity -- a shark species is known to live for more than three centuries. Fully decoded shark genomes will be a tremendous help to research aimed at discovering the molecular bases for these qualities. With this ultimate goal in mind, a research team led by Shigehiro Kuraku at RIKEN BDR analyzed shark genomes using cutting-edge DNA sequencing technologies and comparative bioinformatics that were able to deal with gigabase-scale sequences. They chose two primary species -- the brownbanded bamboo shark and the cloudy catshark -- because they can be raised in aquariums, making it relatively easy to constantly obtain live specimen. They also performed an improved assembly of the whale shark genome, which had been previously released.

Continued  

'Bin chicken' plays unique role in story of evolution

September 28, 2018, University of Queensland

A University of Queensland researcher has uncovered how a French scientist and ibis researcher conducted the first test of evolution more than 50 years before Charles Darwin's Origin of the Species.

UQ Centre for Policy Futures researcher Dr. Caitlin Curtis has found that the sacred ibis – a cousin of the Australian 'bin chicken' – became central to the history of evolution when several mummified birds were taken from Egypt to France in 1798.

"The ibis mummies were taken by Napoleon's army to Paris, and played a surprising role in an early debate about evolution," Dr. Curtis said.

"Two naturalists, Georges Cuvier and Jean-Baptist Lamarck, disagreed about the significance of the mummified Egyptian sacred ibises.

"Cuvier took careful measurements and determined that no changes had happened when comparing the mummified birds against modern specimens.

"He went on to conclude that this was proof that species could not change over time, opposing the emerging evolutionary ideas of Lamarck."

But Lamarck disagreed, arguing not enough time had passed to see any differences, and that environmental conditions would also have had to change.

"This was significant at a time when evolution was not yet an idea," Dr. Curtis said.

"Cuvier was a prominent scientist who had a lot of voice and power within society, and he continued the debate through to Lamarck's death—even criticising Lamarck's belief in evolution at his eulogy – setting back the idea for decades."

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A study of ants provides information on the evolution of social insects

September 10, 2018, Universitaet Mainz

One of the great puzzles of evolutionary biology is what induced certain living creatures to abandon solitary existence in favor of living in collaborative societies, as seen in the case of ants and other social, colony-forming insects. A major characteristic of so-called eusocial species is the division of labor between queens that lay eggs and workers that take care of the brood and perform other tasks. But what is it that determines that a queen should lay eggs and that workers shouldn't reproduce? And how did this distinction come about during the course of evolution? Evolutionary biologist Dr. Romain Libbrecht has been considering these problems over the past years and in cooperation with researchers at Rockefeller University in New York City has found a completely unexpected answer: one single gene called insulin-like peptide 2 (ILP2), which is probably activated by better nutrition, stimulates the ovaries and triggers reproduction.

"It may seem almost inconceivable that just one single gene should make all the difference," Libbrecht pointed out. The researchers drew their conclusion from a comparison of 5,581 genes in seven ant species in four different subfamilies that differ from each other with regard to numerous characteristics. But in one thing are they all alike: there is always a greater expression of ILP2 in the brain of reproductive insects. Queens thus have higher levels than workers. A further finding indicates that this peptide is found only in the brain, where it is produced in a small cluster of just 12 to 15 cells.

Division of reproduction and brood care as the basis of social colony formation

It is postulated that the origins of social behavior in insects are to be found in wasp-like ancestors that alternated between reproduction and brood care phases. A female wasp would lay an egg and take care of the larva until it pupated. However, these two phases were separated and their associated duties assigned to different individuals, namely queens and workers, during the evolution of eusociality.

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