Today, the last remaining stocks of Atlantic walrus are more at danger than ever, due to a combination of Arctic warming and a long history of devastating human exploitation. Rising global temperatures are significantly impacting Arctic marine ecosystems and their inhabitants. However, little is known about exactly how this combination of stress factors will impact Arctic species.

Now, researchers have examined how walrus coped with past cycles of climate change. Using breakthroughs in ancient genomics, the team was able to extract, sequence and interpret ancient genetic information contained in teeth and bone that survive well in the Arctic’s frozen archaeological sites. These DNA results were integrated with modern genetic samples, enabling them to reconstruct how the genetic diversity of Atlantic walrus had changed under earlier cycles of global warming.

“We found that Arctic warming has led to a surprisingly high genetic separation of local walrus stocks. Because they have very specific habitat requirements such as how they feed, for example, this has led to the rapid spreading, isolation and in many cases extinction of walrus stocks,” says Peter Jordan, Professor of Archaeology at Lund University.

The last Ice Age peaked between about 27,000 and 19,000 years ago. At this time the Arctic was buried under kilometers of glacial ice sheets, and so marine mammals were pushed southwards to areas of ice floes and more open water. Walrus survived in some areas of the Atlantic located further to the south, and as soon as climates warmed again, the ice edge retreated and walrus populations pushed quickly northwards again. This combination of warming and climate-driven dispersal led to local walrus populations becoming more genetically differentiated.

In addition, during the last thousand years, human hunting and commercial exploitation has led to numerous local extinction events. These include the expansion of Norse settlers into Iceland and the North Atlantic in pursuit of walrus ivory, which was a valuable trade good, and in more recent times, with industrial scale culling of walrus populations.

Currently, the genetic diversity of walrus stocks is a fragment of what existed earlier, making them even more vulnerable to pressures such as accelerating ice loss, disturbance by Arctic shipping, resource extraction and mass tourism, according to the researchers.

“As Arctic sea ice retreats, the depleted walrus stocks will disperse further into smaller and more isolated pockets, where the genetic isolation and reduced connectivity makes them ever more vulnerable to other stressors such as Arctic shipping, resource extraction and large-scale tourism,” says Peter Jordan.

“Our results underscore the urgency of rethinking conservation goals for species in rapidly changing Arctic marine environments,” he concludes.

Rice University scientists have described in detail the three-dimensional structure of one of the smallest known CRISPR-Cas13 systems used to shred or modify RNA and employed their findings to further engineer the tool to improve its precision. According to a study published in Nature Communications, the molecule works differently than other proteins in the same family.

“There are different types of CRISPR systems, and the one our research was focused on for this study is called CRISPR-Cas13bt3,” said Yang Gao, an assistant professor of biosciences and Cancer Prevention and Research Institute of Texas Scholar who helped lead the study. “The unique thing about it is that it is very small. Usually, these types of molecules contain roughly 1200 amino acids, while this one only has about 700, so that’s already an advantage.”

A diminutive size is a plus as it allows for better access and delivery to target-editing sites, Yang Gao said.

Unlike CRISPR systems associated with the Cas9 protein — which generally targets DNA — Cas13-associated systems target RNA, the intermediary “instruction manual” that translates the genetic information encoded in DNA into a blueprint for assembling proteins.

Researchers hope these RNA-targeting systems can be used to fight viruses, which generally encode their genetic information using RNA rather than DNA.

“My lab is a structural biology lab,” Yang Gao said. “What we are trying to understand is how this system works. So part of our goal here was to be able to see it in three-dimensional space and create a model that would help us explain its mechanism.”

The researchers used a cryo-electron microscope to map the structure of the CRISPR system, placing the molecule on a thin layer of ice and shooting a beam of electrons through it to generate data that was then processed into a detailed, three-dimensional model. The results took them by surprise.

“We found this system deploys a mechanism that’s different from that of other proteins in the Cas13 family,” Yang Gao said. “Other proteins in this family have two domains that are initially separated and, after the system is activated, they come together — kind of like the arms of a scissor — and perform a cut.

“This system is totally different: The scissor is already there, but it needs to hook onto the RNA strand at the right target site. To do this, it uses a binding element on these two unique loops that connect the different parts of the protein together.”

Xiangyu Deng, a postdoctoral research associate in the Yang Gao lab, said it was “really challenging to determine the structure of the protein and RNA complex.”

“We had to do a lot of troubleshooting to make the protein and RNA complex more stable, so we could map it,” Deng said.

Once the team figured out how the system works, researchers in the lab of chemical and biomolecular engineer Xue Sherry Gao stepped in to tweak the system in order to increase its precision by testing its activity and specificity in living cells.

“We found that in cell cultures these systems were able to hone in on a target much easier,” said Sherry Gao, the Ted N. Law Assistant Professor of Chemical and Biomolecular Engineering. “What is really remarkable about this work is that the detailed structural biology insights enabled a rational determination of the engineering efforts needed to improve the tool’s specificity while still maintaining high on-target RNA editing activity.”

Emmanuel Osikpa, a research assistant in the Xue Gao lab, performed cellular assays that confirmed the engineered Cas13bt3 targeted a designated RNA motif with high fidelity.

“I was able to show that this engineered Cas13bt3 performed better than the original system,” Osikpa said. “Xiangyu’s comprehensive study of the structure highlights the advantage that a targeted, structurally guided approach has over large and costly random mutagenesis screening.”

The research was supported by the Welch Foundation (C-2033-20200401, C-1952), the Cancer Prevention and Research Institute of Texas (RR190046), the National Science Foundation (2031242) and the Rice startup fund.

In confirming antimatter and regular matter are gravitationally attracted, the finding also rules out gravitational repulsion as the reason why antimatter is largely missing from the observable universe.

Researchers from the international Antihydrogen Laser Physics Apparatus (ALPHA) collaboration at CERN in Switzerland published their findings today in the journal Nature, an effort supported by more than a dozen countries and private institutions, including the U.S. through the joint U.S. National Science Foundation/Department of Energy Partnership in Basic Plasma Science and Engineering program.

“The success of the ALPHA collaboration is a testament to the importance of teamwork across continents and scientific communities,” says Vyacheslav “Slava” Lukin, a program director in NSF’s Physics Division. “Understanding the nature of antimatter can help us not only understand how our universe came to be but can enable new innovations never before thought possible — like positron emission tomography (PET) scans that have saved many lives by applying our knowledge of antimatter to detect cancerous tumors in the body.”

Matter’s elusive, volatile twin

Beyond the imagined antimatter-fueled warp drives and photon torpedoes of Star Trek, antimatter is completely real, yet mysteriously scarce.

“Einstein’s theory of general relativity says antimatter should behave exactly the same as matter,” said University of California, Berkeley plasma physicist and ALPHA collaboration member Jonathan Wurtele. “Many indirect measurements indicate that gravity interacts with antimatter as expected” he added, “but until the result today, nobody had actually performed a direct observation that could rule out, for example, antihydrogen moving upwards as opposed to downwards in a gravitational field.”

Our bodies, the Earth, and most everything else scientists know about in the universe are overwhelmingly made of regular matter consisting of protons, neutrons, and electrons, like atoms of oxygen, carbon, iron and the other elements of the periodic table.

Antimatter, on the other hand, is regular matter’s twin, though with some opposite properties. For example, antiprotons have a negative charge while protons have a positive charge. Antielectrons (also known as positrons) are positive while electrons are negative.

However, perhaps most challenging for experimenters, “As soon as antimatter touches matter, it blows up,” said ALPHA collaboration member and University of California, Berkeley plasma physicist Joel Fajans.

The combined mass of matter and antimatter is transformed entirely into energy in a reaction so powerful that scientists call it an annihilation.

“For a given mass, such annihilations are the densest form of energy release that we know of,” Fajans added.

But, the amount of antimatter used in the ALPHA experiment is so small that the energy created by antimatter/matter annihilations is perceptible only to sensitive detectors.

“Still, we have to manipulate the antimatter very carefully or we will lose it,” said Fajans.

Dropping an antimatter banger

“Broadly speaking, we’re making antimatter and we’re doing a Leaning Tower of Pisa kind of experiment,” said Wurtele, referring to their experiment’s simpler intellectual ancestor, Galileo’s perhaps apocryphal 16th century experiment demonstrating identical gravitational acceleration of two simultaneously dropped objects of similar volume but different mass. “We’re letting the antimatter go, and we’re seeing if it goes up or down.”

For the ALPHA experiment, the antihydrogen was contained within a tall cylindrical vacuum chamber with a variable magnetic trap, called ALPHA-g. The scientists reduced the strength of the trap’s top and bottom magnetic fields until the antihydrogen atoms could escape and the relatively weak influence of gravity became apparent.

As each antihydrogen atom escaped the magnetic trap, it touched the chamber walls either above or below the trap and annihilated, which the scientists could detect and count.

The researchers repeated the experiment more than a dozen times, varying the magnetic field strength at the top and bottom of the trap to rule out possible errors. They observed that when the weakened magnetic fields were precisely balanced at the top and bottom, about 80% of the antihydrogen atoms annihilated beneath the trap — a result consistent with how a cloud of regular hydrogen would behave under the same conditions.

Thus, gravity was causing the antihydrogen to fall down.

The matter/antimatter mystery

Despite some modest sources of antimatter — like positrons emitted from the decay of potassium, even within a banana — scientists do not see much of it in the universe. However, the laws of physics predict antimatter should exist in roughly equal amounts as regular matter. Scientists call that conundrum the baryogenesis problem.

One potential explanation is that antimatter was gravitationally repelled by regular matter during the big bang, although the new findings suggest that theory no longer seems plausible.

“We’ve ruled out antimatter being repelled by the gravitational force as opposed to attracted,” said Wurtele. That doesn’t mean there isn’t a difference in the gravitational force on antimatter, he adds. Only a more precise measurement will tell.

The ALPHA collaboration researchers will continue to probe the nature of antihydrogen. In addition to refining their measurement of the effect of gravity, they are also studying how antihydrogen interacts with electromagnetic radiation through spectroscopy.

“If antihydrogen were somehow different from hydrogen, that would be a revolutionary thing because the physical laws, both in quantum mechanics and gravity, say the behavior should be the same,” said Wurtele. “However, one doesn’t know until one does the experiment.”

Identifying suitable new habitats will soon become a matter of life or death for some California native species, according to Lawren Sack, a UCLA professor of ecology and evolutionary biology. But if those trees could talk, where would they tell scientists they wanted to live?

In a new study, a team led by Sack and other UCLA biologists deciphered a secret language in leaves and woody stems that points to the species’ optimal habitats. Scientists could use that information to better identify new locations where they could establish new populations of plants and to develop better protections for their existing habitats.

Surprisingly, scientists and conservationists don’t yet have a reliable way to determine the optimal environment for any given plant species; they tend to base their judgments primarily on the locations where plant species currently grow. But for many plants, their current habitats aren’t ideal.

California, for example, has a wealth of species unique to certain climate niches and found nowhere else in the world. But agriculture, industry and urban growth have pushed many of them to the edges of their habitats, and climate change has only exacerbated the problem. So while it might seem logical to move species to habitats like those where they’re currently located or to only protect their current habitats, either approach could imperil the species’ future survival.

The new research, published in Functional Ecology, describes a statistical model that estimates each species’ preferred temperature and amount of rainfall based on its height; the size, wilting point, anatomy and chemical composition of its leaves; and the density of its wood.

Then, using that data, the scientists created a statistical model that predicts what temperatures and rainfall amounts each species preferred — not merely not what it could tolerate. The model also enables the scientists to estimate how mismatched a plant is from its native climate.

“Plant species can directly reveal to us their climate preference and their vulnerability to potential climate change in the ‘language’ of their leaves and wood,” said Sack, the paper’s senior author. “Now that we know this, if you give us a leaf and a piece of wood, we can give a good scientific prediction of where the plant prefers to live.

“We are tuning in to what the plants are telling us about their preferences, in the language of their tissues and physiology, aiming to help them survive escalating climate challenges.”

Sack, working with UCLA postdoctoral scholar Camila Medeiros and an international team analyzed 10 distinct leaf and wood traits from more than 100 species in a range of environments mostly within the University of California Natural Reserve System. The ecosystem types the scientists analyzed — desert, coastal sage scrub, chaparral, montane wet forest, mixed riparian woodland and mixed conifer broadleaf forest — cover about 70% of California’s land area.

“The correspondence of leaf and wood traits with species’ climates is striking,” said Medeiros, the paper’s first author. For example, species native to warmer, drier climates tend to be shorter in stature, with thicker and denser leaves and lower wilting points — traits that enable them to continue photosynthesis when water is scarce and to grow faster when water is more readily available.

“The reflection of species’ preferred climate in their wood and leaves evidently arose from millennia of evolution that matched plant physiology to climate across California,” Medeiros said. “We also found that many plants in the ecosystems we sampled were occupying locations that differed in climate from what we estimated to be their optimal niche. As climate change ensues, we think this will tend to aggravate the sensitivity of many species, including common trees like the California buckeye and shrubs like the purple sage and California lilacs.”

Scientists have long been divided over whether plants’ functional traits could be used to accurately predict their climate preferences. And until now, no test combined all of the available state-of-the art measurement technologies — for example, vapor-pressure osmometry to determine plants’ wilting points — with advanced statistical modeling.

“Some previous studies analyzed individual approaches one by one, but our study was new in simultaneously applying all of them, and this gave us unprecedented predictive power,” Medeiros said.

Medeiros also said the approach could be used to help prioritize which threatened species are most in need of conservation.

The research was funded by the National Science Foundation and the UC Natural Reserve System.

“We can imagine peroxisomes being like miniature factories which specialise in different tasks,” Gatsogiannis explains. “First of all, they are known for ‘detoxifying’ the cell. They act as cellular waste disposal units in our cells.” This waste can be excess fatty acids, for example, or toxic substances from the environment: at least 50 different processes of this kind are attended to by cell organelles only 0.5 micrometres in size (1 micrometre = 1 millionth of a millimetre).

Something that is particularly important for the system is the role played by peroxisomes in fat metabolism. This is because they not only dismantle the fats, they also convert them into usable energy which itself is indispensable for a variety of processes in the body. Without peroxisomes, dangerous quantities of certain fats can accumulate, which would give rise to serious health problems. This is why age-related illnesses are often associated with peroxisomal malfunctions, e.g., loss of hearing or sight, Alzheimer’s, diabetes or cancer.

Each of these processes requires a series of specific enzymes. The peroxisomes, however, are surrounded by a biological membrane which the proteins cannot readily permeate, which means that they have to be imported. This importing mechanism needs energy and a further group of proteins — the Pex group. “Just like a truck, which transports products from one place to another, the transportation of enzymes requires a transportation protein, energy and well-thought out logistics in order to work efficiently,” is the comparison drawn by PhD student Maximilian Rüttermann, a member of the team. “And, again just like a truck, the protein is used again or recycled until ultimately it falls apart or disintegrates.”

This recycling mechanism is the only energy-intensive step in the entire importing process. The main role is played by the perixisomal AAA-ATPase complex Pex1/Pex6: this “biological nanomachine” unpacks and unfolds the spent proteins so that they can be recycled or disposed of. AAA-ATPases are basically a kind of cellular cleaning crew which keeps the inner surroundings of the cell clean, functional and ready for the demands of life. It is less surprising, therefore, that most of the malfunctions in peroxisomal biogenesis are associated with mutations in Pex1 or Pex6, with up to 60 percent of all cases being attributable to a rare genetic disorder in which the patient’s cells are not able to form peroxisomes. This is something which the general public is not aware of, as patients affected die as a rule just a few days or weeks after their birth — and there is no known cure as yet.

The team of researchers headed by Gatsogiannis has now shown, for the first time and in atomic detail, how the peroxisomal AAA-ATPase processes other enzymes in order to keep the detox units functioning properly. To this end the researchers used the cryogenic electron microscopy method. “Investigating a highly dynamic complex such as AAA-ATPase Pex1 Pex 6 is like watching a car engine running,” says Rüttermann. “You generate millions of images from all angles while it’s running and then, on this basis, produce a three-dimensional model in all its various states.” In spring this year, the team put into operation a state-of-the-art cryogenic electron microscope. The new acquisition, costing 7.5 million euros, makes it possible to investigate proteins and biological nanomachines at the atomic level and thus decrypt the secrets of how cells function.

The high-resolution structures show how the Pex1 and Pex6 proteins work together synchronically. They pull out of the membrane a substrate similar to the import receptors used in order to enable them to be recycled — a unique mechanism, comparable to a row of arms which, step by step, pull a thick rope in pairs and, in the process, untie its knots. “The atomic structures and an understanding of the mechanism of this complex nanomachine now enable us to understand important steps in peroxisome physiology in health and disease,” says Gatsogiannis in conclusion. “It is now possible to relate all known mutations to their function, in order to understand their chemical consequences and, as a result, understand the causes of metabolic disorders.”

While plastic pollution is a well-known cause for concern, an often-overlooked issue is how plastics contribute to global warming. Plastics are a surprisingly large cause of carbon emissions, with roughly 4.5% of global emissions caused by the plastics sector.

Now, joint research between Kyushu University and Yokohama-based start-up company, Sotas Co., Ltd, has investigated the potential for Japan’s market to incorporate a greener plastic supply chain.

“The Japanese government has pledged to achieve carbon neutrality by 2050. However, the predominant method that Japan uses to get rid of plastic waste is ‘thermal recycling’ or incineration, which releases carbon dioxide into the atmosphere,” says senior author Professor Andrew Chapman, from Kyushu University’s International Institute for Carbon Neutral Energy and Research. “We have examined whether switching to more sustainable recycled plastics and bioplastics is a competitive and effective alternative to current carbon reduction policies.”

The researchers began with an economic and environmental assessment of six commonly used plastic types, based on whether they were made using virgin, recycled or bioplastic. They scored the plastics using four different criteria: global warming potential, cost, recyclability and perceived quality for manufacturers. Depending on the weighting given to each factor, the researchers calculated how desirable each plastic was under a number of scenarios.

In general, the researchers found that virgin plastics, which are made directly from fossil fuels, are perceived to be the highest quality, but have a high global warming potential and are relatively expensive.

Recycled plastics, on the other hand, are cheaper and also have a lower global warming potential. However, plastics with a higher blend of recycled material were perceived to be of lower quality and recyclability also varied greatly for each plastic type.

“One issue is that it can be physically harder to separate out some types of plastics before recycling and additionally, some plastics can only be recycled a certain number of times,” says first author Yuuki Yoshimoto, President of Sotas Co., Ltd. “It’s therefore important to establish a robust, centralized chain of custody to keep track of how many times a piece of plastic has been recycled to provide quality assurance to end users.”

The analysis also revealed that bioplastics, which are made from plants, have the lowest global warming potential. Some bioplastics can even be carbon-negative, as the plants take in carbon dioxide from the atmosphere as they grow, which is then sequestered in the material.

However, bioplastics are much more costly to make than virgin or recycled plastics, and, as drop-in replacements are not always available, currently perform less well regarding perceived quality. Additionally, starch-based bioplastics require arable land to grow the crops.

“Food versus plastic production is not a fight we want, as land resources are very limited in Japan,” says Prof Chapman. Instead, the researchers suggested further funding for research into cellulose-based bioplastics, which can be sourced from wood pulp.

One additional factor that could help bridge the gap in the cost between bioplastics and virgin plastics is the consumers’ willingness to pay. Prior research suggests that consumers are willing to pay more for environmentally-friendly products, which the researchers plan to investigate in detail and incorporate into their analysis.

“This is a complex situation, with no one-size-fits-all solution,” concludes Yoshimoto. “Ultimately we hope this analysis can help policymakers decide what recycling processes to support, and to inform manufacturers which plastics can best meet their manufacturing and carbon reduction goals.”

This research also considers the economic efficiency of carbon reduction via plastic recycling and bioplastic replacement, broadening the potential policy approaches which can be pursued by policymakers.

Now, Associate Professor Eiman Azim and team have created GlowTrack, a non-invasive movement tracking method that uses fluorescent dye markers to train artificial intelligence. GlowTrack is robust, time-efficient, and high definition — capable of tracking a single digit on a mouse’s paw or hundreds of landmarks on a human hand.

The technique, published in Nature Communications on September 26, 2023, has applications spanning from biology to robotics to medicine and beyond.

“Over the last several years, there has been a revolution in tracking behavior as powerful artificial intelligence tools have been brought into the laboratory,” says Azim, senior author and holder of the William Scandling Developmental Chair. “Our approach makes these tools more versatile, improving the ways we capture diverse movements in the laboratory. Better quantification of movement gives us better insight into how the brain controls behavior and could aid in the study of movement disorders like amyotrophic lateral sclerosis (ALS) and Parkinson’s disease.”

Current methods to capture animal movement often require researchers to manually and repeatedly mark body parts on a computer screen — a time-consuming process subject to human error and time constraints. Human annotation means that these methods can usually only be used in a narrow testing environment, since artificial intelligence models specialize to the limited amount of training data they receive. For example, if the light, orientation of the animal’s body, camera angle, or any number of other factors were to change, the model would no longer recognize the tracked body part.

To address these limitations, the researchers used fluorescent dye to label parts of the animal or human body. With these “invisible” fluorescent dye markers, an enormous amount of visually diverse data can be created quickly and fed into the artificial intelligence models without the need for human annotation. Once fed this robust data, these models can be used to track movements across a much more diverse set of environments and at a resolution that would be far more difficult to achieve with manual human labeling.

This opens the door for easier comparison of movement data between studies, as different laboratories can use the same models to track body movement across a variety of situations. According to Azim, comparison and reproducibility of experiments are essentialin the process of scientific discovery.

“Fluorescent dye markers were the perfect solution,” says first author Daniel Butler, a Salk bioinformatics analyst. Like the invisible ink on a dollar bill that lights up only when you want it to, our fluorescent dye markers can be turned on and off in the blink of an eye, allowing us to generate a massive amount of training data.”

In the future, the team is excited to support diverse applications of GlowTrack and pair its capabilities with other tracking tools that reconstruct movements in three dimensions, and with analysis approaches that can probe these vast movement datasets for patterns.

“Our approach can benefit a host of fields that need more sensitive, reliable, and comprehensive tools to capture and quantify movement,” says Azim. “I am eager to see how other scientists and non-scientists adopt these methods, and what unique, unforeseen applications might arise.”

Other authors include Alexander Keim and Shantanu Ray of Salk.

The work was supported by the UC San Diego CMG Training Program, a Jesse and Caryl Philips Foundation Award, the National Institutes of Health (R00NS088193, DP2NS105555, R01NS111479, RF1NS128898, and U19NS112959), the Searle Scholars Program, the Pew Charitable Trusts, and the McKnight Foundation.

In their newly published study, the researchers describe a new wasp genus Capitojoppa to science, categorising it to the subfamily Ichneumoninae.

“Wasps belonging to this subfamily are usually large and colourful, especially in the tropics, and as larvae feed internally on moth and butterfly caterpillars and pupae. We have studied the biodiversity of ichneumonines in the Allpahuyao-Mishana National Reserve with the samples collected by the researchers of the University of Turku in Finland. In our studies, we have discovered several species unknown to science which we will describe in the future. The current study kicks off this research,” says Doctoral Candidate Brandon Claridge from the Utah State University in the United States.

The Allpahuyao-Mishana National Reserve first gained prominence in the scientific community in the late 1980s when an American botanist Alwyn Gentry documented the highest number of tree species at a single locality known to date.

“Gentry wanted to discover how many tree species can grow in 2.5 acres (one hectare) of the Amazon rainforest. In his study, he discovered nearly 300 tree species in that one 2.5-acres research patch. We have studied the insect biodiversity in the same research areas since 1998 and report some of the highest numbers of insect species in the world from this region. We also found Capitojoppa near the same research hectare used by Gentry,” says Professor of Biodiversity Research Ilari E. Sääksjärvi from the University of Turku, who collected the specimens during his field studies.

Species unknown to science are described in research journals. Their names often describe the species’ characteristics or range.

“The name Capitojoppa tells scientists a great deal about the characteristics of the newly discovered wasp genus. The wasps of the genus have a large head, which is reflected in the capito part of the name. It also refers to the barbet bird genus Capito found in South America, which have a large and strong beak. The joppa part of the name refers to the wasp genus Joppa that the Capitojoppa resembles. The specific species name amazonica refers to the Amazon,” Claridge explains.

Finnish researchers helped in the conservation efforts of the Allpahuayo-Mishana Reserve in the 1990s.

“Allpahuayo-Mishana is a part of the Amazon that has an unprecedented abundance of species. Due to the region’s complex geological history, there are several different types of rainforest growing in the Reserve. The species biodiversity of many organisms is highest on the whole planet at Allpahuayo-Mishana. We actively continue our studies in the region. Unfortunately, the area is currently changing rapidly due to human activities. With our insect studies, we are trying to find out how the impact of human activities, such as climate change, alter the nature in the rainforest,” says Professor Sääksjärvi.

For their study, researchers from Charitéteamed up with the Leibniz Institute for Zoo and Wildlife Research (IZW) to investigate how clearing rainforests to make way for coffee or cacao plantations or human settlements affects the prevalence and biodiversity of mosquitoes and the viruses they carry. The study, which brings together the fields of virology and biodiversity research, was led by Prof. Sandra Junglen, head of the Ecology and Evolution of Arboviruses research group at the Institute of Virology at Charité.

For their research work, the team first caught mosquitoes around Taï National Park in the West African country of Côte d’Ivoire. There is a broad range of land uses there, from pristine rainforest to secondary forest, cacao and coffee plantations, and villages. “We identified the species of mosquitoes we had caught and tested them for viral infections,” explains Kyra Hermanns of the Institute of Virology at Charité, the first author of the study. “Then we looked at how the composition of mosquito species differs across the different land use types, where certain viruses are present, and how prevalent they are.”

Resilient mosquito species prevail over others

There are many different viruses in a healthy ecosystem such as a pristine rainforest. The main reason is that there is a broad range of animal species living there that can carry the virus, acting as hosts. This is because viruses are always tied to their hosts.

If there is a change in the ecosystem, it affects the viruses as well, Junglen explains: “We discovered 49 virus species, with the greatest diversity of hosts and viruses observed in untouched or minimally disturbed habitats.” Most of the 49 different virus species were relatively rare in the areas studied. However, nine of them were commonly found in multiple habitats, with the prevalence of five virus species increasing in habitats that had been disturbed and reaching the highest figures in human settlements.

“This means that the clearing of tropical rainforests causes a decrease in biodiversity across mosquito species, which changes the composition of host types. Some resilient mosquito species have multiplied very successfully in the cleared areas, bringing their viruses with them,” Junglen explains. The composition of a given community of species thus has a direct effect on the prevalence of viruses: “If one host species is very abundant, it is easier for viruses to spread,” the virologist notes. “All of the viruses we found to be more common were demonstrated to be present in a certain mosquito species. The viruses belong to different families and have different properties. That means we were able to show for the first time that the spread of the viruses is attributable not to a close genetic relationship, but to the characteristics of their hosts — especially those mosquito species that adapt well to changing environmental conditions in habitats that have been disturbed.”

New insight into the dynamics of infectious disease

The viruses the researchers found only infect mosquitoes and, as things currently stand, cannot be transmitted to humans. Still, they are a valuable model for understanding how changes in the diversity of a community of species affect the presence and prevalence of viruses. “Our study makes clear just how important biodiversity is, and that decreasing biodiversity makes it easier for certain viruses to thrive because it causes their hosts to become more abundant,” Junglen notes.

“Previously, these kinds of processes were studied almost exclusively using individual pathogens and individual hosts. Now we have a more complete picture that we can use for further research,” she explains. As their next step, the researchers plan to study additional habitats in other countries, with one goal being to pinpoint the exact factors that affect the diversity of mosquito species under land-use change, and the characteristics that viruses need to have in order to spread with their hosts.