An unlikely hero in evolution: worms

JOHNS HOPKINS UNIVERSITY

One of Earth’s most consequential bursts of biodiversity—a 30-million-year period of explosive evolutionary changes spawning innumerable new species—may have the most modest of creatures to thank for the vital stage in life’s history: worms. 

The digging and burrowing of prehistoric worms and other invertebrates along ocean bottoms sparked a chain of events that released oxygen into the ocean and atmosphere and helped kick-start what is known as the Great Ordovician Biodiversification Event, roughly 480 million years ago, according to new findings Johns Hopkins University researchers published in the journal Geochimica et Cosmochimica Acta.

“It’s really incredible to think how such small animals, ones that don’t even exist today, could alter the course of evolutionary history in such a profound way,” said senior author Maya Gomes, an assistant professor in the Department of Earth and Planetary Sciences. “With this work, we’ll be able to examine the chemistry of early oceans and reinterpret parts of the geological record.”

To better understand how changes in oxygen levels influenced large-scale evolutionary events, Gomes and her research team updated models that detail the timing and pace of increasing oxygen over hundreds of millions of years. 

They examined the relationship between the mixing of sediment caused, in part, by digging worms with a mineral called pyrite, which plays a key role in oxygen buildup. The more pyrite that forms and becomes buried under the mud, silt, or sand, the more oxygen levels rise. 

Researchers measured pyrite from nine sites along a Maryland shoreline of the Chesapeake Bay that serves as a proxy for early ocean conditions. Sites with even just a few centimeters of sediment mixing held substantially more pyrite than those without mixing and those with deep mixing.

The findings challenge previous assumptions that the relationship between pyrite and sediment mixing remained the same across habitats and through time, Gomes said. 

Conventional wisdom held that as animals churned up sediments by burrowing in the ocean floor, newly unearthed pyrite would have been exposed to and destroyed by oxygen in the water, a process that would ultimately prevent oxygen from accumulating in the atmosphere and ocean. Mixed sediments have been viewed as evidence that oxygen levels were holding steady. 

The new data suggests that a small amount of sediment mixing in water with very low levels of oxygen would have exposed buried pyrite, sulfur, and organic carbon to just enough oxygen to kick-start the formation of more pyrite.

“It’s kind of like Goldilocks. The conditions have to be just right. You have to have a little bit of mixing to bring the oxygen into the sediment, but not so much that the oxygen destroys all the pyrite and there’s no net buildup,” said Kalev Hantsoo, a doctoral candidate at Johns Hopkins and first author on the article. 

When the researchers applied this new relationship between pyrite and the depth of sediment mixing to existing models, they found oxygen levels stayed relatively flat for millions of years and then rose during the Paleozoic era, with a steep rise occurring during the Ordovician period.

The extra oxygen likely contributed to the Great Ordovician Biodiversification Event, when new species rapidly flourished, the researchers said. 

“There’s always been this question of how oxygen levels relate to the moments in history where evolutionary forces are ramped up and you see a greater diversity of life on the planet,” Gomes said. “The Cambrian period also had a massive speciation event, but the new models allow us to rule out oxygen and focus on other things that may have driven evolution during that time.”

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JOURNAL

Geochimica et Cosmochimica Acta

DOI

10.1016/j.gca.2024.04.018 

ARTICLE TITLE

Trends in estuarine pyrite formation point to an alternative model for Paleozoic pyrite burial

ARTICLE PUBLICATION DATE

1-Jun-2024

 

Syracuse University biologist calls for protection and more studies of natural time capsules of climate change

Ancient rodent nests—or middens—offer critical ecological and evolutionary archives of the last 50,000 years

SYRACUSE UNIVERSITY

 

IMAGE: 

NEOTOMA RODENTS (WOODRATS) IN A NEST, ALSO KNOWN AS A MIDDEN, AT CITY OF ROCKS NATIONAL RESERVE IN IDAHO. PICTURED ARE BOTH A MODERN AND ANCIENT MIDDEN.

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CREDIT: SYRACUSE UNIVERSITY

Packrats, also known as woodrats, are the original hoarders, collecting materials from their environment to make their nests, called middens. In deserts throughout western North America, for instance, packrat middens can preserve plants, insects, bones and other specimens for more than 50,000 years, offering scientists a snapshot into the past. Packrats and numerous other rodent species in dry environments around the world gather plants, insects, bones and other items into their nests from a radius of about 50 feet and urinate over them. The urine dries and crystallizes, hardening the fossils into rock-like masses and preserving the items inside.

Ancient rodent middens have allowed scientists to reconstruct the ecology and climate of semi-arid ecosystems in the Americas, Australia, Africa and the Arabian Peninsula. These natural time capsules are unparalleled archives for observing how plant, animal and microbial species and assemblages have responded over millennia as environmental conditions have changed. Researchers have learned how populations of plants and animals were impacted by climate change in the past, which can provide clues about how populations might respond to future rapid climate disruption.

Today, with advanced molecular technology, scientists can learn more than ever about the ancient organisms that once inhabited the area in and around these middens.

Now, scientists are calling for improved preservation of middens, new research in existing archives and a revival of field studies, according to a prospectus paper recently published online in Trends in Ecology & Evolution. The paper is the result of a multi-year effort involving collaborators from 10 different institutions in the United States, France and Chile, according to Katie Becklin, lead author and assistant professor of biology in Syracuse University’s College of Arts and Sciences.

“New technology in DNA and chemical analysis also allows us to get more information from smaller and smaller amounts of materials,” says Becklin. “We can start to understand what traits are important for predicting which species could do well in the future as climate change continues to impact natural systems.”

But most midden collections are stored at individual institutions where they could be lost or discarded as researchers retire. Midden fossils in the wild meanwhile are vulnerable to destruction by human development and ongoing climate change.

The authors recommend establishing regional depositories for midden materials, which could provide long-term access for researchers. Additional middens must be collected and preserved to stem accelerating losses from land-use conversion, mineral resource extraction, increased wildfire frequency and climate change.

“This is an invitation to the next generation of scientists to take advantage of these resources, to build on the legacy of midden research so far,” says Becklin. “We need to protect these records and make them accessible to the global scientific community and bring in new ideas and people to continue this work.”

Researcher Francisca Diaz, a co-author on the study, sampling middens in the Atacama Desert in South America.

Syracuse biology professor Katie Becklin, lead author of the study.

CREDIT

Syracuse University

JOURNAL

Trends in Ecology & Evolution

ARTICLE TITLE

New uses for ancient middens: bridging ecological and evolutionary perspectives

 

Misleading COVID-19 headlines from mainstream sources did more harm on Facebook than fake news

New MIT Sloan research shows that unflagged but misleading content on Facebook was less persuasive, but much more widely seen, and thus generated more COVID-19 vaccine skepticism than flagged misinformation.

MIT SLOAN SCHOOL OF MANAGEMENT

CAMBRIDGE, Mass., May 30, 2024 – Since the rollout of the COVID-19 vaccine in 2021, fake news on social media has been widely blamed for low vaccine uptake in the United States — but research by MIT Sloan School of Management PhD candidate Jennifer Allen and Professor David Rand finds that the blame lies elsewhere. 

In a new paper published in Science and co-authored by Duncan J. Watts of the University of Pennsylvania, the researchers introduce a new methodology for measuring social media content’s causal impact at scale. They show that misleading content from mainstream news sources — rather than outright misinformation or “fake news” — was the primary driver of vaccine hesitancy on Facebook. 

A new approach to estimating impact

“Misinformation has been correlated with many societal challenges, but there’s not a lot of research showing that exposure to misinformation actually causes harm,” explained Allen. 

During the COVID-19 pandemic, for example, the spread of misinformation related to the virus and vaccine received significant public attention. However, existing research has, for the most part, only established correlations between vaccine refusal and factors such as sharing misinformation online — and largely overlooked the role of “vaccine-skeptical” content, which was potentially misleading but not flagged as misinformation by Facebook fact-checkers. 

To address that gap, the researchers first asked a key question: What would be necessary for misinformation or any other type of content to have far-reaching impacts? 

“To change behavior at scale, content has to not only be persuasive enough to convince people not to get the vaccine, but also widely seen,” Allen said. “Potential harm results from the combination of persuasion and exposure.”

To quantify content’s persuasive ability, the researchers conducted randomized experiments in which they showed thousands of survey participants the headlines from 130 vaccine-related stories — including both mainstream content and known misinformation — and tested how those headlines impacted their intentions to get vaccinated against COVID-19. Researchers also asked a separate group of respondents to rate the headlines across various attributes, including plausibility and political leaning. One factor reliably predicted impacts on vaccination intentions: the extent to which a headline suggested that the vaccine was harmful to a person’s health. 

Using the “wisdom of crowds” and natural language processing AI tools, Allen and her co-authors extrapolated those survey results to predict the persuasive power of all 13,206 vaccine-related URLs that were widely viewed on Facebook in the first three months of the vaccine rollout. By combining these predictions with data from Facebook showing the number of users who viewed each URL, the researchers could predict each headline’s overall impact — the number of people it might have persuaded not to get the vaccine. The results were surprising. 

The underestimated power of exposure

Contrary to popular perceptions, the researchers estimated that vaccine-skeptical content reduced vaccination intentions 46 times more than misinformation flagged by fact-checkers. 

The reason? Even though flagged misinformation was more harmful when seen, it had relatively low reach. In total, the vaccine-related headlines in the Facebook data set received 2.7 billion views — but content flagged as misinformation received just 0.3% of those views, and content from domains rated as low-credibility received 5.1%. 

“Even though the outright false content reduced vaccination intentions the most when viewed, comparatively few people saw it,” explained Rand. “Essentially, that means there’s this class of gray-area content that is less harmful per exposure but is seen far more often —and thus more impactful overall — that has been largely overlooked by both academics and social media companies.”

Notably, several of the most impactful URLs within the data set were articles from mainstream sources that cast doubt on the vaccine’s safety. For instance, the most-viewed was an article — from a well-regarded mainstream news source — suggesting that a medical doctor died two weeks after receiving the COVID-19 vaccine. This single headline received 54.9 million views — more than six times the combined views of all flagged misinformation. 

While the body of this article did acknowledge the uncertainty of the doctor’s cause of death, its “clickbait” headline was highly suggestive and implied that the vaccine was likely responsible. That’s significant since the vast majority of viewers on social media likely never click out to read past the headline. 

How journalists and social media platforms can help

According to Rand, one implication of this work is that media outlets need to take more care with their headlines, even if that means they aren’t as attention-grabbing. 

“When you are writing a headline, you should not just be asking yourself if it’s false or not,” he said. “You should be asking yourself if the headline is likely to cause inaccurate perceptions.” 

For platforms, added Allen, the research also points to the need for more nuanced moderation — across all subjects, not just public health. 

“Content moderation focuses on identifying the most egregiously false information — but that may not be an effective way of identifying the most overall harmful content,” she says. “Platforms  should also prioritize reviewing content from the people or organizations with the largest numbers of followers while balancing freedom of expression. We need to invest in more research and creative solutions in this space – for example, crowdsourced moderation tools like X’s Community Notes.”

“Content moderation decisions can be really difficult because of the inherent tension between wanting to mitigate harm and allowing people to express themselves,” Rand said. “Our paper introduces a framework to help balance that trade-off by allowing tech companies to actually quantify potential harm.”

And the trade-offs could be large. An exploratory analysis by the authors found that if Facebook users hadn’t been exposed to this vaccine-skeptical content, as many as 3 million more Americans could have been vaccinated. 

“We can’t just ignore this gray area-content,” Allen concluded. “Lives could have been saved.”

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JOURNAL

Science

DOI

10.1126/science.adk3451 

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Quantifying the impact of misinformation and vaccine-skeptical content on Facebook

ARTICLE PUBLICATION DATE

30-May-2024

 

Cuckoos evolve to look like their hosts - and form new species in the process

Peer-Reviewed Publication

UNIVERSITY OF CAMBRIDGE

 

VIDEO: 

A LARGE-BILLED GERYGONE HOST PULLS A LITTLE BRONZE-CUCKOO CHICK OUT OF ITS NEST

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CREDIT: HEE-JIN NOH

The theory of coevolution says that when closely interacting species drive evolutionary changes in each other this can lead to speciation - the evolution of new species. But until now, real-world evidence for this has been scarce.

Now a team of researchers has found evidence that coevolution is linked to speciation by studying the evolutionary arms race between cuckoos and the host birds they exploit.

Bronze-cuckoos lay their eggs in the nests of small songbirds. Soon after the cuckoo chick hatches, it pushes the host’s eggs out of the nest. The host not only loses all its own eggs, but spends several weeks rearing the cuckoo, which takes up valuable time when it could be breeding itself.

 Each species of bronze-cuckoo closely matches the appearance of their host’s chicks, fooling the host parents into accepting the cuckoo.

The study shows how these interactions can cause new species to arise when a cuckoo species exploits several different hosts. If chicks of each host species have a distinct appearance, and hosts reject odd-looking nestlings, then the cuckoo species diverges into separate genetic lineages, each mimicking the chicks of its favoured host. These new lineages are the first sign of new species emerging.

“This exciting new finding could potentially apply to any pairs of species that are in battle each other. Just as we’ve seen with the cuckoo, the coevolutionary arms race could cause new species to emerge - and increase biodiversity on our planet,” said Professor Kilner in the University of Cambridge’s Department of Zoology, a co-author of the report.

The striking differences between the chicks of different bronze-cuckoo lineages correspond to subtle differences in the plumage and calls of the adults, which help males and females that specialise on the same host to recognise and pair with each other.

“Cuckoos are very costly to their hosts, so hosts have evolved the ability to recognise and eject cuckoo chicks from their nests,’’ said Professor Naomi Langmore at the Australian National University, Canberra, lead author of the study. 

She added: “Only the cuckoos that most resemble the host’s own chicks have any chance of escaping detection, so over many generations the cuckoo chicks have evolved to mimic the host chicks.”

The study revealed that coevolution is most likely to drive speciation when the cuckoos are very costly to their hosts, leading to a ‘coevolutionary arms race’ between host defences and cuckoo counter-adaptations.

A broad scale analysis across all cuckoo species found that those lineages that are most costly to their hosts have higher speciation rates than less costly cuckoo species and their non-parasitic relatives.

“This finding is significant in evolutionary biology, showing that coevolution between interacting species increases biodiversity by driving speciation,” said Dr Clare Holleley at the Australian National Wildlife Collection within CSIRO, Canberra, senior author of the report.

The study was made possible by the team’s breakthrough in extracting DNA from eggshells in historical collections, and sequencing it for genetic studies.

The researchers were then able to combine two decades of behavioural fieldwork with DNA analysis of specimens of eggs and birds held in museums and collections.

The paper is published today in the journal Science.

The study involved an international team of researchers at the University of Cambridge, Australian National University, CSIRO (Australia’s national science agency), and the University of Melbourne. It was funded by the Australian Research Council.

A male superb fairy-wren brings food to a Horsfield’s bronze-cuckoo fledgling. 

Only cuckoos that most resemble the host’s own chicks have any chance of escaping detection. Over many generations the cuckoo chicks have evolved to mimic the host chicks.

CREDIT

Mark Lethlean

Cuckoo nestlings mimic the nestlings of their host bird 

Bronze-cuckoo nestlings on the left with the nestlings of their hosts on the right.

TOP ROW: little bronze-cuckoo, host large-billed gerygone.

SECOND ROW: shining bronze-cuckoo, host yellow-rumped thornbill.

THIRD ROW: Horsfield’s bronze-cuckoo, host superb fairy-wren.

CREDIT

Naomi Langmore

Subspecies of cuckoo mimic the chicks of their host in appearance 

Subspecies of the little bronze-cuckoo and the shining bronze-cuckoo track the appearance of their host’s chicks across their geographic range.

Image shows:

A. Little bronze-cuckoo and mangrove gerygone host.

B. Little bronze-cuckoo and large-billed gerygone host.

C. Little bronze-cuckoo and fairy gerygone host.

D. Shining bronze-cuckoo and yellow-rumped thornbill host.

E. Shining bronze-cuckoo and fan-tailed gerygone host.

F. Shining bronze-cuckoo and grey warbler host.

CREDIT

Naomi Langmore, Hee-Jin Noh, Rose Thorogood, Alfredo Attisano

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JOURNAL

Science

DOI

10.1126/science.adj3210 

ARTICLE TITLE

Coevolution with hosts underpins speciation in brood-parasitic cuckoos

ARTICLE PUBLICATION DATE

30-May-2024

 

New coral disease forecasting system led by University of Hawai'i team

UNIVERSITY OF HAWAII AT MANOA

 

IMAGE: 

THE GREAT BARRIER REEF, SEEN FROM A SCENIC FLIGHT NEAR AIRLIE BEACH, QUEENSLAND. 

 

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CREDIT: AYANADAK123, WIKIMEDIA COMMONS.

Research led by the University of Hawaiʻi at Mānoa Hawaiʻi Institute of Marine Biology (HIMB) has led to a new tool for forecasting coral disease that could help conservationists step in at the right times with key interventions. Ecological forecasts are critical tools for conserving and managing marine ecosystems, but few forecasting systems can account for the wide range of ecological complexities in near-real-time.

Using ecological and marine environmental conditions, the Multi-Factor Coral Disease Risk product predicts the risk of two diseases across reefs in the central and western Pacific and along the east coast of Australia. An article introducing the new tool was published in Ecological Applications.

The tool can be accessed through the U.S. National Oceanic and Atmospheric Administration (NOAA) Coral Reef Watch program, and can help end users detect early changes in the environment and better protect coral reef ecosystems.

“Partnering with NOAA Coral Reef Watch, our team developed ecological forecasts to predict the times and conditions when coral disease outbreaks are most likely to occur,” said NASA-funded Principal Investigator and HIMB Interim Director Megan Donahue.

“We are really excited about this new tool,” said lead author, Jamie Caldwell, of High Meadows Environmental Institute at Princeton University. “Users can employ this tool to make decisions about how to manage coral health, similar to how we use weather forecasts to decide how to pack for an upcoming trip.”

More than half a billion people depend on Earth’s coral reefs, and ensuring their resilience in the face of many threats is an ongoing challenge for managers. Tools like this help ensure these vital ecosystems survive.

Understanding localized risks

Insights gleaned from the tool can help managers better understand localized risks of coral disease and develop timely strategies for intervention.

“A key project element was the consultation with and input from coral reef managers from across the Pacific, including here in Australia,” said Professor Scott Heron, a collaborator from James Cook University. “We’ve also provided several training sessions in the various aspects of how the tool is used so that stakeholders in the varying locations have the best opportunity to inform effective reef management.”

Coral reefs are the most biologically diverse, species-rich marine ecosystem on Earth. They are culturally significant to Indigenous people throughout the world, and they provide food, jobs, recreation, medicine and coastline protection from storms and erosion. While disease is a natural part of marine ecosystems, increased runoff, global climate change and a slough of human impacts stress corals and cause disease.

The Multi-Factor Coral Disease Risk Product was developed by HIMB, in close collaboration with NOAA Coral Reef Watch, James Cook University, University of Newcastle and University of New South Wales.

Deep coral ecosystems 

Mesophotic coral ecosystems, such as this one found at 230 feet in Maui's 'Au'au Channel, are populated with many of the same fish species found on shallow reefs.

 

CREDIT

NOAA and Hawaii Undersea Research Laboratory

Jamie Caldwell conducts a coral health survey on Hawaiʻi Island. 

CREDIT

Courtney Couch

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JOURNAL

Ecological Applications

DOI

10.1002/eap.2961 

METHOD OF RESEARCH

Computational simulation/modeling

ARTICLE TITLE

Multi-Factor Coral Disease Risk: A new product for early warning and management

 

Trout in mine-polluted rivers are genetically ‘isolated’

UNIVERSITY OF EXETER

 

IMAGE: 

A BROWN TROUT

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CREDIT: DANIEL OSMOND

Trout living in rivers polluted by metal from old mines across the British Isles are genetically “isolated” from other trout, new research shows.

Researchers analysed brown trout at 71 sites in Britain and Ireland, where many rivers contain metal washed out from disused mines.

While trout in metal-polluted rivers appear healthy, they are genetically distinct – and a lack of diversity in these populations makes them vulnerable to future threats.

By comparing the DNA of trout in rivers with and without metal pollution, the researchers found that metal-tolerant trout populations split from the wider species during periods of peak mining activity.  

The study, by the universities of Exeter and Cardiff, was carried out in four regions: west Wales, northeast England, southwest England and southeast Ireland.

“We found massively reduced genetic diversity in some of these trout populations inhabiting metal-impacted waters,” said Professor Jamie Stevens, from the University of Exeter.

“These fish carry a high burden of metals, with toxic binding of dissolved metals to their gills causing suffocation, but trout that can tolerate this have emerged in polluted rivers.

“If fish without this tolerance swim into these rivers, they must either leave or die from that exposure.

“This means the metal-tolerant fish are genetically isolated, not exchanging genes with other trout populations.

“So, while these fish may be healthy where they are, the genetic diversity that allowed them to adapt to this rapid change in their environment is now lacking – leaving them more vulnerable to future changes.”

Common metal pollutants in former mining areas include lead and copper, and many fish and other species in these rivers have already been wiped out.

The emergence of metal-resistant trout, with high genetic differentiation from neighbouring populations and reduced diversity, was seen in populations inhabiting metal-polluted rivers in Cornwall, Wales and northeast England.

“This is likely the result of selection pressure – evolution driven in this case by survival, or non-survival, depending on the ability to withstand metal pollution,” said Dr Daniel Osmond, of the  Westcountry Rivers Trust, who conducted the research as part of his PhD at Exeter.

The study found the highest levels of genetic isolation in rivers that were both polluted with metal and affected by physical barriers such as dams and weirs.

Metal pollution levels fluctuate, often rising during periods of high rainfall.

Dr Osmond explained: “Throughout different periods of history, these mined regions have been globally important in their industrial production of many metals. This however has left polluted landscapes such as West Cornwall, which is effectively a giant honeycomb of old mines.

“When rain comes, these can fill with water and that can flow out into rivers.”

Freshwater migratory fish have declined significantly in many areas and, while trout are not considered to be a threatened species, the study shows trout may be more vulnerable than previously believed.

The researchers say that reducing mine water wash-out and the removal of physical barriers in rivers could help to reduce genetic isolation.

The study used simulations of populations through time, modelling different historical evolutionary scenarios and the effects of these on the genetic diversity of populations, comparing these with the sampled populations today, to predict which evolutionary scenarios were most credible.

Funders of the research included the Natural Environment Research Council, the Game & Wildlife Conservation Trust and the EU Interreg SAMARCH project.

The paper, published in the journal Diversity and Distributions, is entitled: “Living in a post-industrial landscape: repeated patterns of genetic divergence in brown trout (Salmo trutta L.) across the British Isles.”

Mine water flowing into the River Ystwyth

CREDIT

Daniel Osmond

JOURNAL

Diversity and Distributions

DOI

10.1111/ddi.13854 

ARTICLE TITLE

Living in a post-industrial landscape: repeated patterns of genetic divergence in brown trout (Salmo trutta L.) across the British Isles.

ARTICLE PUBLICATION DATE

30-May-2024