Nano-sensor detects pesticides on fruit in minutes

Peer-Reviewed Publication

KAROLINSKA INSTITUTET

 

IMAGE: FLAME NANOPARTICLE DEPOSITION WAS USED TO PRODUCE ROBUST NANO-SENSORS THAT CAN DETECT PESTICIDE RESIDUES ON APPLE SURFACES WITHIN MINUTES. view more 

CREDIT: ARTWORK BY HAIPENG LI AND GEORGIOS A SOTIRIOU.

Researchers at Karolinska Institutet in Sweden have developed a tiny sensor for detecting pesticides on fruit in just a few minutes. The technique, described as a proof-of-concept in a paper in the journal Advanced Science, uses flame-sprayed nanoparticles made from silver to increase the signal of chemicals. While still at an early stage, the researchers hope these nano-sensors could help uncover food pesticides before consumption.

“Reports show that up to half of all fruits sold in the EU contain pesticide residues that in larger quantities have been linked to human health problems,” says Georgios Sotiriou, principal researcher at the Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, and the study’s corresponding author. “However, current techniques for detecting pesticides on single products before consumption are restricted in practice by the high cost and cumbersome manufacturing of its sensors. To overcome this, we developed inexpensive and reproducible nano-sensors that could be used to monitor traces of fruit pesticides at, for example, the store.”

The new nano-sensors employ a 1970s discovery known as surface-enhanced Raman scattering, or SERS, a powerful sensing technique that can increase the diagnostic signals of biomolecules on metal surfaces by more than 1 million times. The technology has been used in several research fields, including chemical and environmental analysis as well as to detect biomarkers for various diseases. However, high production costs and limited batch-to-batch reproducibility have so far hindered widespread application in food safety diagnostics.

Flame spray technology

In the current study, the researchers created a SERS nano-sensor by using flame spray – a well-established and cost-effective technique for depositing metallic coating – to deliver small droplets of silver nanoparticles onto a glass surface.

“The flame spray can be used to quickly produce uniform SERS films across large areas, removing one of the key barriers to scalability,” says Haipeng Li, a postdoctoral researcher in Sotiriou’s lab and the study’s first author.

The researchers then finetuned the distance between the individual silver nanoparticles to enhance their sensitivity. To test their substance-detecting ability, they applied a thin layer of tracer dye on top of the sensors and used a spectrometer to uncover their molecular fingerprints. The sensors reliably and uniformly detected the molecular signals and their performance remained intact when tested again after 2,5 months, which underscores their shelf life potential and feasibility for large-scale production, according to the researchers.

Detected pesticides on apples

To test the sensors’ practical application, the researchers calibrated them to detect low concentrations of parathion-ethyl, a toxic agricultural insecticide that is banned or restricted in most countries. A small amount of parathion-ethyl was placed on part of an apple. The residues were later collected with a cotton swab that was immersed in a solution to dissolve the pesticide molecules. The solution was dropped on the sensor, which confirmed the presence of pesticides.

“Our sensors can detect pesticide residues on apple surfaces in a short time of five minutes without destroying the fruit,” Haipeng Li says. “While they need to be validated in larger studies, we offer a proof-of-concept practical application for food safety testing at scale before consumption.”

Next, the researchers want to explore if the nano-sensors can be applied to other areas such as discovering biomarkers for specific diseases at the point-of-care in resource-limited settings.

The research was funded by the European Research Council (ERC), Karolinska Institutet, the Swedish Foundation for Strategic Research (SSF) and the Swedish Research Council.

Publication: “SERS Hotspot Engineering by Aerosol Self-Assembly of Plasmonic Ag Nanoaggregates with Tunable Interparticle Distance.” Haipeng Li, Padryk Merkl, Jens Sommertune, Thomas Thersleff, and Georgios A. Sotiriou, Advanced Science, online June 7, 2022, doi: 10.1002/advs.202201133

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JOURNAL

Advanced Science

DOI

10.1002/advs.202201133 

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

“SERS Hotspot Engineering by Aerosol Self-Assembly of Plasmonic Ag Nanoaggregates with Tunable Interparticle Distance"

ARTICLE PUBLICATION DATE

7-Jun-2022

Indigenous Borneans knew a tree was two distinct species— genetic analysis confirms they were right

Peer-Reviewed Publication

CELL PRESS

 

IMAGE: THIS IMAGE SHOWS A LUMOK PINGAN FRUIT (LEFT) AND A LUMOK AMAT FRUIT (LEFT). view more 

CREDIT: GARDENER ET AL./CURRENT BIOLOGY

Over 200 years ago, a Spanish botanist described Artocarpus odoratissimus, a species of fruit-bearing tree found in Borneo and the Philippines. The Iban people, who are indigenous to Borneo, know the tree to have two different varieties, which they call lumok and pingan, distinguished by their fruit size and shape. Despite this knowledge, Western botanists have long considered the tree as a single species, but a genetic analysis, published June 6 in the journal Current Biology, confirms the Iban people were right all along.

To determine the correct taxonomy of the tree, which is in the same genus as the trees that produce the meaty jackfruit, scientists took DNA samples from trees in Malaysian Borneo and from historical herbarium specimens. They employed phylogenetic analyses and DNA microsatellites to show that while lumok and pingan are closely related, they are genetically distinct species. The scientists recommend that the trees be renamed to reflect this and suggest that it’s time to consider incorporating Indigenous names into taxonomic research.

“While the scientific endeavor has long benefitted from Indigenous knowledge, it has usually not engaged with it on equal footing,” write the authors, which include Malaysian scientists and Iban field botanists, led by Elliot M. Gardner (@elliotmgardner), a botanist at Florida International University. “While Linnaean taxonomy offers a broad framework for global comparisons, it may lack the detailed local insights possessed by Indigenous peoples.”

“Time is of the essence, because just as biodiversity is under threat of climate change, Indigenous knowledge—itself protected under Article 8(j) of the Convention on Biological Diversity—is threatened by societal change,” Gardner and colleagues say.

###

This work was supported by the National Science Foundation, the Garden Club of America, the American Society of Plant Taxonomists, the Botanical Society of America, the Systematics Association, the Linnean Society, EU-SYNTHESYS, and the Garfield Weston foundation.

Current Biology, Gardner et al: “Engagement with indigenous knowledge improves our understanding of biodiversity and promotes the conservation of both” https://www.cell.com/current-biology/fulltext/S0960-9822(22)00680-7

Current Biology (@CurrentBiology), published by Cell Press, is a bimonthly journal that features papers across all areas of biology. Current Biology strives to foster communication across fields of biology, both by publishing important findings of general interest and through highly accessible front matter for non-specialists. Visit: http://www.cell.com/current-biology. To receive Cell Press media alerts, contact press@cell.com.

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JOURNAL

Current Biology

DOI

10.1016/j.cub.2022.04.062 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Engagement with indigenous knowledge improves our understanding of biodiversity and promotes the conservation of both

ARTICLE PUBLICATION DATE

6-Jun-2022

Exotic tree plantations can disturb local wildlife, researchers find

Peer-Reviewed Publication

UNIVERSITY OF BRISTOL

 

IMAGE: COPROPHANAEUS LANCIFER, THE LARGEST DUNG BEETLE SPECIES IN THE STUDY REGION view more 

CREDIT: HANNAH GRIFFITHS

Initiatives using non-native tree species can impact tropical insects in neighbouring forests, according to an international study.

Scientists at the University of Bristol and Federal University of Western Pará, in Brazil have found that Eucalyptus plantation edge effects radiates up to 800 meters into the interior of nearby Amazonian forests, when applied to ecologically important dung beetles.

As the world seeks to mitigate human-induced climate change, planted forests have become widespread restoration strategy across the globe. However the findings, published today in Forest Ecology and Management, suggest that while well-intentioned, exotic tree plantations can have a wider influence on the native biodiversity of hyperdiverse tropical forests.

In ecology, edge effect research investigates how biological populations or communities change at the boundary of two or more habitats.

To further understand the edge effect, the team of scientists travelled to the Amazon Rainforest and collected over 3,700 dung beetles from 49 species to evaluate how Eucalyptus plantations affect the insect biodiversity in neighbouring Amazonian forests.

“Our findings for dung beetles offer new insights into the importance of considering how proximity to exotic tree plantations can affect tropical forest biodiversity,” said Dr Filipe França of Bristol’s School of Biological Sciences, and co-supervisor of the lead author.

He said: “Importantly, edge effects varied across dung beetle responses and were species-specific. For example, we found more dung beetle species far away from Eucalyptus plantations, but some species also thrived and had higher abundances closer to plantation edges.”

This means that some dung beetles may be more sensitive to changes in forest environment closer to exotic tree plantations than others edge-affiliated and generalist species.

“Understanding multi-species responses to anthropogenic disturbances is crucial to tackle the current biodiversity crisis and our findings are vital for forest managers and conservation planners aiming to maintain forest-specialist biodiversity in native ecosystems across the tropics,” explained Professor Rodrigo Fadini from the Federal University of Western Pará.

  

CAPTION

Canthon fulgidus, a roller-dung beetle species in the study region

CREDIT

Dr Filipe França

Paper:

‘Edge effects from exotic tree plantations and environmental context drive dung beetle assemblages within Amazonian undisturbed forests’ by  Maria Katiane Costa, Filipe França, Carlos Brocardo, and Rodrigo Fadini in Forest Ecology and Management.

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JOURNAL

Forest Ecology and Management

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Edge effects from exotic tree plantations and environmental context drive dung beetle assemblages within Amazonian undisturbed forests

ARTICLE PUBLICATION DATE

7-Jun-2022

Beyond “plant trees!”: UMBC research finds tree plantations encroaching on essential ecosystems

Trees planted in the tropics as part of nations’ reforestation commitments can have unintended consequences, sometimes degrading biodiversity hotspots, damaging ecosystems like grasslands, or encroaching on protected areas

Peer-Reviewed Publication

UNIVERSITY OF MARYLAND BALTIMORE COUNTY

 

IMAGE: TREES SUPPLY MANY BENEFITS, AND MANY NATIONS HAVE COMMITTED TO REFORESTING LARGE SWATHS OF LAND AS PART OF THEIR EFFORTS TO ADDRESS CLIMATE CHANGE. AS AN EXAMPLE, THIS IS A TEAK PLANTATION IN COSTA RICA. HOWEVER, NEW RESEARCH FROM UMBC FINDS THAT SOME TREES PLANTED IN THE TROPICS MAY DO MORE HARM THAN GOOD. THE AUTHORS FOUND THAT 92 PERCENT OF NEW TREE PLANTATIONS PLANTED IN THE TROPICS BETWEEN 2000 AND 2012 WERE IN BIODIVERSITY HOTSPOTS. FOURTEEN PERCENT WERE IN ARID BIOMES, WHERE TREES ARE UNLIKELY TO THRIVE AND LIKELY TO DAMAGE EXISTING ECOSYSTEMS LIKE GRASSLANDS, WHICH ARE HEROES OF CARBON SEQUESTRATION IN THEIR OWN RIGHT. TREE PLANTATIONS HAD ALSO ENCROACHED INTO 9 PERCENT OF ACCESSIBLE PROTECTED AREAS IN THE HUMID TROPICS, SUCH AS NATIONAL PARKS. “WE NEED TO BE COGNIZANT THAT NOT ALL TREE PLANTING IS BENEFICIAL FOR THE ECOSYSTEM INVOLVED,” SAYS MATTHEW FAGAN, THE LEAD AUTHOR ON THE NEW STUDY. “THE RIGHT TREE IN THE RIGHT PLACE IS THE RIGHT ANSWER.” view more 

CREDIT: MATTHEW FAGAN

Trees store carbon, filter the air, create habitat, and supply a host of other benefits for animals and people. Planting the right trees, in the right places, in consultation with local communities, can support goals like addressing climate change and improving lives. However, new research led by Matthew Fagan, assistant professor of geography and environmental systems at UMBC, finds that some trees planted in the tropics may be doing more harm than good.

The study, published in Nature Sustainability, examined the increase in tree cover across the global tropics between 2000 and 2012. Fagan and colleagues found that, surprisingly, tree cover gains during that period were equally attributable to natural forest regrowth and the creation of tree plantations. The most common tree plantation species were rubber, eucalyptus, and oil palm.

Tree plantations are not always harmful to the environment, and even much-maligned oil palm can be farmed sustainably, Fagan explains. However, the study found that 92 percent of new tree plantations were in biodiversity hotspots, threatening a range of plant and animal species. Also, 14 percent of plantations were in arid biomes, where trees are unlikely to thrive and likely to damage existing ecosystems. And tree plantations had encroached into 9 percent of accessible protected areas in the humid tropics, such as national parks.

“Ecologists have been sounding the alarm on this for over a decade,” Fagan says. “But no one’s had a hard number about how much this is actually happening.”

When tree planting is lose-lose

In recent years, dozens of nations have committed to restoring large areas of forest. Tree plantations make up 45 percent of commitments to the Bonn Challenge, an international initiative to restore degraded and deforested landscapes. But Fagan is concerned that these plantations may have unintended consequences.

For example, China has undertaken a massive tree-planting effort at the edge of the Gobi desert, and many African countries have committed to planting trees at the transition between the Sahara desert and Sahel grassland. The goal is to prevent desert expansion, but the plantings can cause harm. Disturbing the soil releases carbon, and trees are water hogs. They end up “killing off the grassland that was there, and then they often die of drought,” Fagan says. In these situations, tree planting is lose-lose.

Similarly, in Brazil, soy farmers moved out of the Amazon and into the Cerrado, one of the world’s largest savannas. Pine and eucalyptus tree farms followed. The Cerrado supports a wealth of biodiversity, and the carbon it stores underground rivals rainforest carbon sequestration, Fagan explains. Tree crops in the Cerrado may count toward Brazil’s reforestation commitment, but could actually be a step backward in mitigating climate change and biodiversity loss.

“In the U.S., we have a huge area of relatively wet woods, and we tend to idolize planting trees as sort of the ultimate environmental act,” Fagan says. “But there’s a lot of value in grasslands and savannas that we don’t necessarily see. And when you plant trees, you essentially destroy that ecosystem.”

In response to his team’s new research, “I would really like to see governments around the world reassess their restoration plans,” Fagan says, “or at least be more transparent when their plans involve tree planting, especially in areas that may not be appropriate for planting trees.”

Park or plantation?

Fagan’s new paper also revealed the extent to which tree plantations are invading protected areas. The problem was so bad that he had to overhaul the algorithm his team used to differentiate between data representing natural forest regrowth and tree plantations.

Initially, the algorithm used park boundaries as a proxy for natural forest regrowth areas. But it wasn’t working. To figure out what was wrong, Fagan spot-checked 20 parks, and found that three had multiple plantations inside them. That got him curious.

Six weeks later, he had manually checked for plantations in every park in the tropics. When he found plantations, he either redrew the park’s boundaries or, if the park was too compromised, removed it from the data completely. Using the resulting new maps, the algorithm could detect natural forest regrowth versus tree plantations with more than 90 percent accuracy.

“It was very disturbing to see there were just so many parks that were compromised,” Fagan says.

The new maps allowed the team to find many more regrowth areas and plantations than expected from government estimates. Several UMBC undergraduates are authors on the paper because of their contributions to this data analysis. Each student manually checked at least 1,000 patches, some as many as 3,000.

“In the end, the tropics is a much more modified place than we were expecting,” Fagan says. “There’s a whole host of reasons that we see these encroachments, but they’re definitely happening all over the world. We see a steady erosion of these parks by plantations, and the industry is just getting started.”

Reason for hope

When setting out on this research, the team had a simple question: How many planted trees are there in the world? “It seemed like a strange thing not to know,” Fagan says. As the work progressed, they asked whether trees were being planted where they shouldn’t be and whether plantations were expanding into parks. They’ve found the results concerning, but they also have reason for hope.

Trees can do a lot of good, and planting more of them can be a significant factor in addressing the impacts of climate change. But it has to be done right. “This paper shows it’s possible to monitor natural forest versus plantation at a global scale,” Fagan says, “so we can encourage the results we want and discourage results we don’t want.”

He also hopes the results will inspire everyone to be more conscious of where their products—from paper to food to shampoo to tires—come from, and to demand that companies producing those products in tree plantations adopt more sustainable practices.

“If we make our choices en masse, it does shift the direction that these companies go in,” Fagan says. And despite our love for trees in the U.S., he notes, forests are not the only ecosystems that can help mitigate the effects of climate change and biodiversity loss. Savannas and prairies also have an important role to play.

“We need to be cognizant that not all tree planting is beneficial for the ecosystem involved,” Fagan says. “The right tree in the right place is the right answer.”

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JOURNAL

Nature Sustainability

DOI

10.1038/s41893-022-00904-w 

METHOD OF RESEARCH

Imaging analysis

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

The expansion of tree plantations across tropical biomes

ARTICLE PUBLICATION DATE

6-Jun-2022

Hubble Space Telescope captures largest near-infrared image to find universe’s rarest galaxies

Peer-Reviewed Publication

UNIVERSITY OF TORONTO

 

IMAGE: A PATCH OF SKY IMAGED BY 3D-DASH, SHOWING THE BRIGHTEST AND RAREST OBJECTS OF THE UNIVERSE LIKE MONSTER GALAXIES. view more 

CREDIT: GABE BRAMMER

TORONTO, ON – An international team of scientists today released the largest near-infrared image ever taken by NASA’s Hubble Space Telescope, enabling astronomers to map the star-forming regions of the universe and learn how the earliest, most distant galaxies originated. Named 3D-DASH, this high-resolution survey will allow researchers to find rare objects and targets for follow-up observations with the recently launched James Webb Space Telescope (JWST) during its decades-long mission.

A preprint of the paper to be published in The Astrophysical Journal is available on arXiv.

“Since its launch more than 30 years ago, the Hubble Space Telescope has led a renaissance in the study of how galaxies have changed in the last 10-billion years of the universe,” says Lamiya Mowla, Dunlap Fellow at the Faculty of Arts & Science’s Dunlap Institute for Astronomy & Astrophysics at the University of Toronto and lead author of the study. “The 3D-DASH program extends Hubble’s legacy in wide-area imaging so we can begin to unravel the mysteries of the galaxies beyond our own.”

For the first time, 3D-DASH provides researchers with a complete near-infrared survey of the entire COSMOS field, one of the richest data fields for extragalactic studies beyond the Milky Way. As the longest and reddest wavelength observed with Hubble – just past what is visible to the human eye – near-infrared means astronomers are better able to see the earliest galaxies that are the farthest away.

Astronomers also need to search a vast area of the sky to find rare objects in the universe. Until now, such a large image was only available from the ground and suffered from poor resolution, which limited what could be observed. 3D-DASH will help to identify unique phenomena like the universe’s most massive galaxies, highly active black holes, and galaxies on the brink of colliding and merging into one.

CAPTION

Galaxies from the last 10 billion years witnessed in the 3D-DASH program, created using 3D-DASH/F160W and ACS-COSMOS/F814W imaging.

CREDIT

Lamiya Mowla

“I am curious about monster galaxies, which are the most massive ones in the universe formed by the mergers of other galaxies. How did their structures grow, and what drove the changes in their form?” says Mowla, who began work on the project in 2015 while a grad student at Yale University. “It was difficult to study these extremely rare events using existing images, which is what motivated the design of this large survey.”

CAPTION

Lamiya Mowla, Dunlap Fellow at the Faculty of Arts & Science’s Dunlap Institute for Astronomy & Astrophysics at the University of Toronto and lead author of the study.

CREDIT

Courtesy of Lamiya Mowla

To image such an expansive patch of sky, the researchers employed a new technique with Hubble known as Drift And SHift (DASH). DASH creates an image that is eight times larger than Hubble’s standard field of view by capturing multiple shots that are then stitched together into one master mosaic, similar to taking a panoramic picture on a smartphone.

DASH also takes images faster than the typical technique, snapping eight pictures per Hubble’s orbit instead of one picture, achieving in 250 hours what would previously have taken 2,000 hours.

“3D-DASH adds a new layer of unique observations in the COSMOS field and is also a steppingstone to the space surveys of the next decade,” says Ivelina Momcheva, head of data science at the Max Planck Institute for Astronomy and principal investigator of the study. “It gives us a sneak peek of future scientific discoveries and allows us to develop new techniques to analyze these large datasets.”

3D-DASH covers a total area almost six times the size of the moon in the sky as seen from Earth. This record is likely to remain unbroken by Hubble’s successor JWST, which is instead built for sensitive, close-up images to capture fine detail of a small area. It is the largest near-infrared image of the sky available to astronomers until the next generation of telescopes launch in the next decade, such as the Nancy Grace Roman Space Telescope and Euclid.

3D-DASH depth map (IMAGE)

UNIVERSITY OF TORONTO

CAPTION

Zoomed-in panels on the 3D-DASH depth map reveal the wealth of bright objects that can be studied.

CREDIT

Mowla et al. 2022

3D-DASH mosaicing video (VIDEO)

UNIVERSITY OF TORONTO

CAPTION

The Hubble Space Telescope captured the entire COSMOS field by stitching together multiple images into one master image, a process called mosaicing

CREDIT

Ivelina Momcheva

Until then, professional astronomers and amateur stargazers alike can explore the skies using an interactive, online version of the 3D-DASH image created by Gabriel Brammer, professor at the Cosmic Dawn Center in the Niels Bohr Institute, University of Copenhagen.

The Hubble Space Telescope is a project of international cooperation between NASA and European Space Agency (ESA). NASA's Goddard Space Flight Center manages the telescope in Greenbelt, Maryland. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.

The full image is available at the Mikulski Archive for Space Telescopes.

-30-

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JOURNAL

The Astrophysical Journal

DOI

10.1021/acs.est.2c01204 

METHOD OF RESEARCH

Imaging analysis

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

3D-DASH: The Widest Near-Infrared Hubble Space Telescope Survey

How species form: What the tangled history of polar bear and brown bear relations tells us

It’s complicated. Rather than simple splitting events, the species histories of polar and brown bears, like those of humans, hide convoluted stories of divergence and interbreeding, study finds

Peer-Reviewed Publication

UNIVERSITY AT BUFFALO

 

IMAGE: A MOTHER POLAR BEAR AND HER 2-YEAR-OLD CUBS IN NORTHWESTERN GREENLAND. view more 

CREDIT: CREDIT: ØYSTEIN WIIG

BUFFALO, N.Y. — A new study is providing an enhanced look at the intertwined evolutionary histories of polar bears and brown bears.

Becoming separate species did not completely stop these animals from mating with each other. Scientists have known this for some time, but the new research draws on an expanded dataset — including DNA from an ancient polar bear tooth — to tease out more detail.

The story that emerges reveals complexities similar to those that complicate human evolutionary history.

“The formation and maintenance of species can be a messy process,” says Charlotte Lindqvist, PhD, associate professor of biological sciences in the University at Buffalo College of Arts and Sciences, and an expert on bear genetics. “What’s happened with polar bears and brown bears is a neat analog to what we’re learning about human evolution: that the splitting of species can be incomplete. As more and more ancient genomes have been recovered from ancient human populations, including Neanderthals and Denisovans, we’re seeing that there was multidirectional genetic mixing going on as different groups of archaic humans mated with ancestors of modern humans. Polar bears and brown bears are another system where you see this happening.”

“We find evidence for interbreeding between polar bears and brown bears that predates an ancient polar bear we studied,” she says. “And, moreover, our results demonstrate a complicated, intertwined evolutionary history among brown and polar bears, with the main direction of gene flow going into polar bears from brown bears. This inverts a hypothesis suggested by other researchers that gene flow has been unidirectional and going into brown bears around the peak of the last ice age.”

The study will be published the week of June 6 in the Proceedings of the National Academy of Sciences. It was led by Lindqvist at UB in the U.S.; Luis Herrera-Estrella at the National Laboratory of Genomics for Biodiversity (LANGEBIO) in Mexico and Texas Tech University in the U.S.; and Kalle Leppälä at the University of Oulu in Finland. Tianying Lan, PhD, a former UB postdoctoral researcher now at Daicel Arbor Biosciences, was co-first author with Leppälä.

The concept of Arctic-adapted polar bears capturing genetic material from brown bears, which are adapted to life in lower latitudes, is one of several findings of possible interest for scientists concerned with climate change impacts on threatened species.

As the world warms and Arctic sea ice declines, polar bears and brown bears may run into each other more frequently in places where their ranges overlap. This makes their shared evolutionary history a particularly intriguing subject of study, Lindqvist says.

CAPTION

An adult male polar bear in northwestern Greenland.

CREDIT

Credit: Øystein Wiig

Splitting of species can be a messy process

As Lindqvist explains, scientists once thought modern humans and Neanderthals simply split into separate species after evolving from a common ancestor. Then, researchers found Neanderthal DNA in modern Eurasian people, implying that modern human populations received an influx of genes from Neanderthals at some point in their shared evolutionary history, she says.

Only later did scientists realize that this genetic intermingling also supplemented Neanderthal populations with modern human genes, Lindqvist adds. In other words, interbreeding can be complex, not necessarily a one-way street, she says.

The new study on bears reveals a remarkably similar story: The analysis finds evidence of hybridization in both polar bear and brown bear genomes, with polar bears in particular carrying a strong signature of an influx of DNA from brown bears, researchers say. Earlier research proposed the inverse pattern only, Lindqvist says.

“It’s exciting how DNA can help reveal ancient life history. Gene flow direction is harder to determine than merely its presence, but these patterns are vital to understanding how past adaptations have transferred among species to give modern animals their current features,” says Leppälä, PhD, postdoctoral researcher in the research unit of mathematical sciences at the University of Oulu.

“Population genomics is an increasingly powerful toolbox to study plant and animal evolution and the effects of human activity and climate change on endangered species,” says Herrera-Estrella, PhD, President’s Distinguished Professor of Plant Genomics and director of the Institute of Genomics for Crop Abiotic Stress Tolerance in the Texas Tech Department of Plant and Soil Science. He is also a professor emeritus at LANGEBIO. “Bears don’t provide simple speciation stories any more than human evolution has. This new genomic research suggests that mammalian species groups can hide complicated evolutionary histories.”

CAPTION

The subfossil jawbone of a polar bear that lived 115,000 to 130,000 years ago in Norway’s Svalbard archipelago. A genomic study includes an analysis of DNA extracted from a tooth attached to this jawbone, which is now housed at the Natural History Museum at the University of Oslo.

CREDIT

Credit: Photo by Karsten Sund, Natural History Museum (NHM), University of Oslo

CAPTION

The subfossil jawbone of a polar bear that lived 115,000 to 130,000 years ago in Norway’s Svalbard archipelago. A genomic study includes an analysis of DNA extracted from a tooth attached to this jawbone, which is now housed at the Natural History Museum at the University of Oslo.

CREDIT

Credit: Photo by Karsten Sund, Natural History Museum (NHM), University of Oslo

Evidence from modern bear genomes — and DNA from an ancient tooth

The study analyzed the genomes of 64 modern polar and brown bears, including several new genomes from Alaska, a state where both species are found.

The team also produced a new, more complete genome for a polar bear that lived 115,000 to 130,000 years ago in Norway’s Svalbard archipelago. DNA for the ancient polar bear was extracted from a tooth attached to a subfossil jawbone, which is now housed at the Natural History Museum at the University of Oslo.

Using this dataset, researchers estimate that polar bears and brown bears started to become distinct species about 1.3 to 1.6 million years ago, updating prior assessments made by some of the same scientists. The age of the split has been and remains a topic of scientific debate, with past interbreeding and limited fossil evidence for ancient polar bears among factors that make the timing hard to pinpoint, Lindqvist says.

In any case: After becoming their own species, polar bears endured dramatic population decline and a prolonged genetic bottleneck, leaving these bears with much less genetic diversity than brown bears, the new study concludes. The findings confirm past research pointing to the same trends, and add evidence in support of this hypothesis.

Together with the analysis of gene flow, these findings are providing new insights into the messy, intertwined evolutionary history of polar bears and brown bears.

The international research team included scientists from UB, LANGEBIO, Texas Tech, the University of Oulu, the Far Northwestern Institute of Art and Science, the Alaska Department of Fish and Game, the Natural History Museum at the University of Oslo, Nanyang Technological University, University of Helsinki, and Aarhus University.

The research was funded by the National Fish and Wildlife Foundation, U.S. National Science Foundation, Alaska Department of Fish and Game, and U.S. Geological Survey.

CAPTION

Genomes analyzed in a new study on bears include that of this bear, pictured here in 1995 on Alaska's North Slope. Scientists had wondered if this bear might be a brown bear-polar bear hybrid, but the new research finds that, “This bear is not a hybrid, but simply a light-colored brown bear,” says University at Buffalo biologist Charlotte Lindqvist.

CREDIT

Credit: Richard Shideler, Division of Wildlife Conservation, Alaska Department of Fish and Game

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JOURNAL

Proceedings of the National Academy of Sciences