The ancestor of all modern birds probably had iridescent feathers

A family tree of 9,409 bird species helped scientists figure out why there are so many colorful birds in the tropics and how these colors spread over time

FIELD MUSEUM

 

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BIRDS-OF-PARADISE IN THE FIELD MUSEUM'S COLLECTIONS

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CREDIT: KATE GOLEMBIEWSKI, FIELD MUSEUM

The color palette of the birds you see out your window depend on where you live. If you’re far from the Equator, most birds tend to have drab colors, but the closer you are to the tropics, you’ll probably see more and more colorful feathers. Scientists have long been puzzled about why there are more brilliantly-colored birds in the tropics than in other places, and they’ve also wondered how those brightly-colored birds got there in the first place: that is, if those colorful feathers evolved in the tropics, or if tropical birds have colorful ancestors that came to the region from somewhere else. In a new study published in the journal Nature Ecology and Evolution, scientists built a database of 9,409 birds to explore the spread of color across the globe. They found that iridescent, colorful feathers originated 415 times across the bird tree of life, and in most cases, arose outside of the tropics– and that the ancestor of all modern birds likely had iridescent feathers, too.

“For decades, scientists have had this hypothesis that there are brighter or more colorful species of birds in the tropics,” says Chad Eliason, a research scientist at the Field Museum in Chicago and the paper’s lead author. “We wanted to find the mechanism to help us understand these trends-- how these bright colors got there and how they spread across the bird family tree over time.”

There are two main ways that color is produced in animals: pigments and structures. Cells produce pigments like melanin, which is responsible for black and brown coloration. Meanwhile, structural color comes from the way light bounces off different arrangements of cell structures. Iridescence, the rainbow shimmer that changes depending how light hits an object, is an example of structural color.

Tropical birds get their colors from a combination of brilliant pigments and structural color. Eliason’s work focuses on structural color, so he wanted to explore that element of tropical bird coloration. He and his colleagues combed through photographs, videos, and even scientific illustrations of 9,409 species of birds-- the vast majority of the 10,000-ish living bird species known to science. The researchers kept track of which species have iridescent feathers, and where those birds are found.

The scientists then combined their data on bird coloration and distribution with a pre-existing family tree, based on DNA, showing how all the known bird species are related to each other. They fed the information to a modeling system to extrapolate the origins and spread of iridescence. “Basically, we did a lot of math,” says Eliason.

Given how modern species are related to each other and where they're found, and overall patterns of how species form and how traits like colors change over time, the modeling software determined the most likely explanation for the bird colors we see today: colorful birds from outside the tropics often came to the region millions of years ago, and then branched out into more and more different species. The model also revealed a surprise about the ancestor of all modern birds.

For background, birds are a specialized group of dinosaurs-- the earliest known bird, Archaeopteryx, lived 140 million years ago. A sub-group of birds called Neornithes evolved 80 million years ago, and this group became the only birds (and dinosaurs) to survive the mass extinction 66 million years ago. All modern birds are members of Neornithes. The model produced by Eliason and his colleagues suggests that the common ancestor of all Neornithes, 80 million years ago, had iridescent feathers that still glitter across the bird family tree.

“I was very excited to learn that the ancestral state of all birds is iridescence,” says Eliason. “We’ve found fossil evidence of iridescent birds and other feathered dinosaurs before, ​​by examining fossil feathers and the preserved pigment-producing structures in those feathers. So we know that iridescent feathers existed back in the Cretaceous-- those fossils help support the idea from our model that the ancestor of all modern birds was iridescent too.”

The discovery that the first Neornithes was likely iridescent could have important implications for paleontology. ”We’re probably going to be finding a lot more iridescence in the fossil record now that we know to look,” says Eliason.

While this new study sheds light on how iridescence spread through the bird family tree over the course of millions of years, some big questions remain. “We still don’t know why iridescence evolved in the first place,” says Eliason. “Iridescent feathers can be used by birds to attract mates, but iridescence is related to other aspects of birds’ lives too. For instance, tree swallows change color when the humidity changes, so iridescence could be related to the environment, or it might be related to another physical property of feathers, like water resistance. But knowing more about how there came to be so many iridescent birds in the tropics might help us understand why iridescence evolved.”

This study was contributed to by Chad M. Eliason of the Field Museum’s Grainger Bioinformatics Center and Negaunee Integrative Research Center, Michaël P.J. Nicolaï of Ghent University and the Royal Belgian Institute of Natural Sciences, Cynthia Bom of Vrije Universiteit Amsterdam, Eline Blom of Naturalis Biodiversity Center, Liliana D’Alba of Ghent University and Naturalis Biodiversity Center, and Matthew D. Shawkey of Ghent University.

 

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Lead author Chad Eliason with hummingbirds in the Field Museum's collections.

CREDIT

Kate Golembiewski, Field Museum

A blue-headed sunbird in the Albertine Rift: an example of a tropical bird with iridescent, colorful feathers. 

CREDIT

John Bates, Field MuseumJOURNAL

Nature Ecology & Evolution

ARTICLE TITLE

Why are there so many structurally coloured bird species in the tropics?

ARTICLE PUBLICATION DATE

26-Jul-2024

 

A soft needle in an oceanic haystack

Rare discovery of new soft-bodied vertebrate fossil in American Great Basin region will augment understanding of vertebrate evolution

HARVARD UNIVERSITY

 

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NUUCICHTHYS RHYNCHOCEPHALUS IS THE FIRST SOFT-BODIED VERTEBRATE FROM THE AMERICAN GREAT BASIN. 

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CREDIT: FRANZ ANTHONY

The Cambrian fossil record indicates that most animal phyla had diversified and inhabited the Earth’s oceans approximately 518 million years ago. But even though chordates—the group that includes vertebrates like humans—were part of this early animal diversification, they make up a relatively small portion of fossils from more than 50 Cambrian sites worldwide.

In a new paper published in Royal Society Open Science, Harvard research scientist Rudy Lerosey-Aubril and associate professor Javier Ortega-Hernández present their surprising finding of a new species of chordate, and the first soft-bodied vertebrate to be discovered in the Drumian Marjum Formation of the American Great Basin.

This new fossil was part of a collection of Cambrian soft-bodied fossils deposited in the Museum of Natural History of Utah, a long term collaborator with researchers at Harvard.

The discovery of this new species, dubbed Nuucichthys rhynchocephalus, is a valuable contribution to early vertebrate evolution and biodiversity because of the dearth of these types of organisms in Cambrian fossil sites—including South China, the Northeastern United States, and British Columbia.

Nuucichthys is also one of only four species documenting the early evolutionary stage of vertebrate lineage and, as such, is one of humanity’s oldest relatives.

In their paper, Lerosey-Aubril and Ortega-Hernández describe Nuucichthys as having a finless torpedo-shaped body that includes a number of markers characteristic of vertebrates.

“Early vertebrates start to have big eyes and a series of muscle blocks that we call myotomes, and this is something we recognize very well in our fossil,” Lerosey-Aubril said.

The new species also confirms that, despite their overall similarities to larval fish—having a cavity that is a sort of rudimentary gill system—they were devoid of fins and therefore had limited swimming capabilities.

“But all of these characteristics clearly point to some vertebrate affinities,” Lerosey-Aubril said. “And because it's very early in the evolution of the vertebrates, they don't have bones yet—this is why these fossils are exceedingly rare.”

Lerosey-Aubril and Ortega-Hernández speculate that Nuucichthys likely lived high up in the water column of the ocean. Because of this, and because it possessed no biomineralized parts like bones or a shell, it was particularly prone to rapid post-mortem degradation and decay, which explains why they were fossilized so rarely.

“What’s interesting with this new species is that understanding how the morphology evolved from the invertebrate type to the vertebrate type is difficult without fossils, and this new fossil tells us a little bit about that,” Ortega-Hernández said.

The Drumian Marjum site where the new fossil was found has been intensively investigated since 2022 by an international group of paleontologists led by Lerosey-Aubril and Ortega-Hernández, and both believe that continuous collecting efforts at this site may result in the discovery of new specimens of Nuucichthys rhynchocephalus in the future.

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JOURNAL

Royal Society Open Science

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

A long-headed Cambrian soft-bodied vertebrate from the American Great Basin region

ARTICLE PUBLICATION DATE

24-Jul-2024

 

Ancient DNA analyses imply brucellosis evolved with development of farming

TRINITY COLLEGE DUBLIN

 

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THE 8,000-YEAR-OLD SHEEP BONE FROM WHICH DNA WAS EXTRACTED.

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CREDIT: DR KEVIN DALY

Scientists believe the bacterial infection brucellosis, which affects millions of people every year and causes significant harm to the welfare of livestock, may have evolved along with the development of farming. They came to this conclusion after performing analyses of ancient DNA extracted from an 8,000-year-old sheep bone, in which the Brucella melitensis pathogen was detected.

Passed on by the consumption of unpasteurised milk and close contact with infected animals, brucellosis can cause waves of undulating fever and, tragically, the infection-related loss of pregnancy in pregnant women. Now, researchers have recovered a millennia-old genome of the sheep, goat, and human-infecting pathogen.

Recently published in the leading journal Nature Communications, the study reveals that the pathogen responsible for most brucellosis infections, Brucella melitensis, existed over 8,000 years ago in Neolithic times. 

Pathogen evolution and ancient DNA

How long have we lived with disease-causing pathogens? How and when did the pathogens which infect both humans and animals – known as zoonoses – evolve? And did we play a role in their evolution? These are questions which have long challenged researchers, particularly due to the difficulty of studying the deep past. 

But recent advances in the field of ancient DNA – the sequencing of genomes from organisms thousands of years in the past, from DNA typically preserved in bones and teeth – have allowed these questions to be directly addressed.

Ancient Brucella

In this study an international team of geneticists and archaeologists succeeded in detecting the Brucella in DNA from an 8,000-year-old sheep bone from Menteşe Höyük, an archaeological settlement in Northwest Türkiye, which shows the pathogen was circulating in herds of the world's first animal farmers.

“Looking for ancient pathogen DNA is like looking for a needle in a haystack,” says Louis L'Hôte, PhD student in Trinity College Dublin’s School of Genetics and Microbiology, and lead author of the study.

“It requires well preserved DNA and the presence of the infectious agent during the life of the animal. We were lucky enough to detect the presence of Brucella melitensis in Menteşe Höyük, which is a sign that the bacteria was infecting livestock during the Neolithic.” 

The evolution of different pathogens

Using the genome, the researchers were able to time when Brucella melitensis, which typically infects sheep and goats, evolved from its shared ancestor with Brucella abortus, which mostly infects cattle. They estimate that this happened ~9,800 years ago, in a period known as the Neolithic, when crop and livestock farming first developed. 

Intriguingly, this overlaps with when livestock keeping had become more developed, with farming communities keeping a mixture of animals. 

Farming and pathogen host-jumping

“By bringing together animals such as sheep, goat, cattle and pigs, which may rarely have lived in the same spaces together, early livestock farmers may have created an evolutionary melting pot for pathogen host-jumping, says Dr Kevin Daly, Ad Astra Assistant Professor at University College Dublin (and formerly of Trinity), who supervised the study. 

“For as long as we have kept animals as livestock, humanity has risked disease exposure – a problem we still grapple with 10,000 years later,” he adds.

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JOURNAL

Nature Communications

DOI

10.1038/s41467-024-50536-1 

 

CU Anschutz scientists identify key protein behind spread of shingles virus

For the first time, researchers identify the mechanism that allows the varicella zoster virus to spread far from the infection site

UNIVERSITY OF COLORADO ANSCHUTZ MEDICAL CAMPUS

 

VIDEO: 

THE VARICELLA ZOSTER VIRUS, WHICH RESIDES IN OVER 95% OF US, CAUSES CHICKEN POX AND THE MORE SERIOUS SHINGLES INFECTION.  CUANSCHUTZ RESEARCHERS HAVE DISCOVERED HOW THE VIRUS SPREADS SO RAPIDLY THROUGHOUT OUR BODIES, WHICH HAS OPENED A PATH TO FINDING A TREATMENT THAT COULD STOP SHINGLES AND ITS RELATED COMPLICATIONS.

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CREDIT: UNIVERSITY OF COLORADO ANSCHUTZ MEDICAL CAMPUS

AURORA, Colo. (July 25, 2024) –  Scientists at the University of Colorado Anschutz Medical Campus have discovered a new evasion strategy used by the varicella zoster virus, which causes chickenpox and shingles, that may allow it to affect tissues far from the original site of infection.

The study was published today in the Journal of Virology.

The researchers, using human neurons and rodent models, honed in on a single viral protein known as IE62 that is packaged and shuttled throughout the body in structures known as small extracellular vesicles (sEVs). They discovered that IE62 packaged inside sEVs can travel from the site of infection, where it penetrates cells and shuts down their antiviral response, opening the door to infection by the virus.

The virus, known as VZV, is ancient and common, residing within 95% of all people. Its primary infection causes chickenpox, which then goes latent. During stress, aging, or other factors, VZV can reactivate into shingles, a painful skin disease that can also attack the central nervous system and can lead to vascular disease, stroke, dementia, and other serious conditions.

To rapidly spread throughout the body, the virus needs an immediate strategy to evade the immune system. This study is the first to show exactly how it does this by exploiting the infected cells sEV machinery.

“This is the first time a clear mechanism has been found that actually ties this virus to an avenue by which it can affect distal organs, far from the site of infection,” said the study’s first author, Christy Niemeyer, PhD, assistant professor of neurology at the University of Colorado School of Medicine.  “These vesicles shut down the immune response.”

The study’s senior author Andrew Bubak, PhD, assistant professor of neurology at the CU School of Medicine, said the protein shuts down the anti-viral response in the cells far sooner than previously known.

“We believe this protein is likely being packaged into sEVs and shuttled down the neurons that go to your skin, making the cells under the skin vulnerable to the whole infection,” Bubak said. “We think this precedes the rash, which is obviously interesting from a therapeutic standpoint.”

While there is a vaccine for shingles, there are currently no drugs to impact the activity of this protein. That could change.

“This study is the first to identify a different anti-viral target that perhaps we can develop therapeutics for,” Niemeyer said.

Bubak said this mechanism may be responsible for the prevalent co-infections and immunosuppressive events seen clinically in those infected with VZV. He also noted that the virus can intermittently reactivate in individuals without the classic shingles rash, evading diagnosis and raising the question of whether this immunosuppressive event occurs more frequently than originally thought.

“This mechanism can offer us clues into how other viruses work and cause infection,” he said.

Niemeyer agreed, saying the significance of sEVs in the spread of this virus highlights the need for further investigation.

“We need to better understand their role in viral spread and secondary disease development to reduce the systemic complications caused by VZV infections,” she said.

About the University of Colorado Anschutz Medical Campus

The University of Colorado Anschutz Medical Campus is a world-class medical destination at the forefront of transformative science, medicine, education and patient care. The campus encompasses the University of Colorado health professional schools, more than 60 centers and institutes, and two nationally ranked independent hospitals - UCHealth University of Colorado Hospital and Children's Hospital Colorado - that treat more than two million adult and pediatric patients each year. Innovative, interconnected and highly collaborative, the University of Colorado Anschutz Medical Campus delivers life-changing treatments, patient care and professional training and conducts world-renowned research fueled by over $705 million in research grants. For more information, visit www.cuanschutz.edu.

 

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JOURNAL

Journal of Virology

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Animal tissue samples

ARTICLE TITLE

Suppression of the host antiviral response by non-infectious varicella zoster virus extracellular vesicles

ARTICLE PUBLICATION DATE

25-Jul-2024

 

Physical employment standards move beyond tactical settings to ensure workplace safety

A special section of WORK: A Journal of Prevention, Assessment & Rehabilitation highlights the varying physical elements, requirements, and applications of Physical Employment Standards frameworks for a range of physically demanding occupations

IOS PRESS

 

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THE PHYSICAL EMPLOYMENT STANDARDS (PES) SEEK TO MOVE BEYOND THE PUSH-UPS TO INCLUDE OCCUPATIONAL-RELEVANT PHYSICAL ASSESSMENTS

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CREDIT: BOND UNIVERSITY.

Amsterdam, July 25, 2024 – A standard methodology for the development of Physical Employment Standards (PES) in tactical settings like the military and first responder agencies is being used internationally. PES are now being developed for other physically active occupations to support personnel undertaking physically demanding tasks. A special section of an issue of WORK: A Journal of Prevention, Assessment & Rehabilitation, published by IOS Press (now part of Sage), highlights the varying physical elements and requirements for different occupations and the subsequent applications of PES frameworks.

Guest editor Professor Rob Orr, from the Tactical Research Unit and Faculty of Health Sciences and Medicine at Bond University in Australia, explains, "Organizations face challenges in the development and implementation of PES. How can they bridge the gap between science and organizational practices? How can they sustain recruitment amid declining fitness levels? And how can they measure success? Another challenge lies in effectively balancing the physical, cognitive, and psychosocial demands in the workplace to ensure that individuals and teams can fulfill all aspects of their job roles, not just the physical requirements."

The physical elements and requirements for different occupations, and even within occupational subgroups, can vary and as such, job tasks analysis and subsequent PES need to be developed specifically for a given occupation. PES are being used to assess physical capacity in order to ensure that individuals can perform necessary physical tasks safely and effectively. PES can help:

• Establish a baseline level of physical fitness or capabilities required for specific roles
• Mitigate the risk of employing physically unfit individuals in physically demanding jobs, which can be costly, both in human and economic terms
• Ensure that an employee is physically capable of completing the tasks of a job to at least the minimum acceptable standard, and provide employees and potential employees with a target to reach and sustain
• Decrease the potential for injury, thereby providing a “duty of care” to all employees
• Base retirement or transition to a less physical role on capacity rather than an arbitrary age
• Provide feedback on rehabilitation and return to work
• Encourage self-training, self-evaluation and a healthier lifestyle
• Increase confidence of individuals and teams

Dr. Gemma Milligan, the Chair of the PES committee, notes, "Going forward, we envision the expansion of the PES methodology to aid in physical conditioning and return-to-work planning for personnel. Another benefit of the application of PES is that it can support the recording of data to enable the subsequent review and success of PES. Finally, we see the exploration of female/age-inclusive versus female/age-specific solutions as a promising future avenue."

 

Editor-in-Chief of WORK Karen Jacobs, OT, EdD, OTR, CPE, FAOTA, Sargent College of Health and Rehabilitation Sciences, Boston University, adds, “I am delighted to publish a special issue that spotlights the diverse physical elements, requirements, and applications of PES frameworks across a spectrum of physically demanding occupations. This issue represents a significant milestone in our understanding of occupational fitness, and it's incredibly exciting to be at the forefront of such pivotal discussions.”

This special section of the journal WORK contains 16 contributions concerned with the identification of tasks, physical requirements to perform tasks, and assessment batteries and associated outcomes. It is based on the Fourth International Physical Employment Standards Conference on Perspectives, Themes and Future Direction held at Bond University, Gold Coast, Australia, in February 2023, which was attended by researchers, practitioners, and policymakers working within the military, law enforcement, fire and rescue, paramedicine, astronautics, sport, and industry sectors from 10 nations.

 

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JOURNAL

Work

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Special Section: Physical Employment Standards

 

New understanding of fly behavior has potential application in robotics, public safety

Mechanical Engineering professor publishes findings in Current Biology

Peer-Reviewed Publication

UNIVERSITY OF NEVADA, RENO

 

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ASSISTANT PROFESSOR FLORIS VAN BREUGEL AND POSTDOCTORAL RESEARCHER DAVID STUPSKI HAVE UNCOVERED AN AUTOMATIC BEHAVIOR IN FLIES, SINK AND CIRCLE, WHICH INVOLVES LOWERING ALTITUDE AND REPETITIVE, RAPID TURNS IN A CONSISTENT DIRECTION. IT SHOWS THAT FLYING FLIES ARE ABLE TO ASSESS THE CONDITIONS OF THE WIND BEFORE DEPLOYING A STRATEGY TO FIND A ODOR (WHICH LEADS TO A FOOD SOURCE) USING A STRATEGY THAT WILL WORK WELL UNDER THOSE CONDITIONS. FLIES AREN'T JUST REACTING TO AN ODOR WITH A PREPROGRAMMED RESPONSE: THEY ARE RESPONDING IN CONTEXT-APPROPRIATE MANNER. THIS KNOWLEDGE POTENTIALLY COULD BE APPLIED TO TRAIN MORE SOPHISTICATED ALGORITHMS FOR SCENT-DETECTING DRONES TO FIND CHEMICAL LEAKS. 

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CREDIT: CHRIS MORAN

RENO, Nevada — Why do flies buzz around in circles when the air is still? And why does it matter?

In a paper published online July 26, 2024 by the scientific journal Current Biology, University of Nevada, Reno Assistant Professor Floris van Breugel and Postdoctoral Researcher S. David Stupski respond to this up-until-now unanswered question. And that answer could hold a key to public safety — specifically, how to better train robotic systems to track chemical leaks.

“We don’t currently have robotic systems to track odor or chemical plumes,” van Breugel said. “We don’t know how to efficiently find the source of a wind-borne chemical. But insects are remarkably good at tracking chemical plumes, and if we really understood how they do it, maybe we could train inexpensive drones to use a similar process to find the source of chemicals and chemical leaks.”

A fundamental challenge in understanding how insects track chemical plumes — basically, how does the fly find the banana in your kitchen? — is that wind and odors can’t be independently manipulated.

To address this challenge, van Breugel and Stupski used a new approach that makes it possible to remotely control neurons—specifically the “smell” neurons— on the antennae of flying fruit flies by genetically introducing light-sensitive proteins, an approach called optogenetics. These experiments, part of a $450,000 project funded through the Air Force Office of Scientific Research, made it possible to give flies identical virtual smell experiences in different wind conditions.

What van Breugel and Stupski wanted to know: how do flies find an odor when there’s no wind to carry it? This is, after all, likely the wind experience of a fly looking for a banana in your kitchen. The answer is in the Current Biology article, “Wind Gates Olfaction Driven Search States in Free Flight.” The print version will appear in the Sept. 9 issue.

Flies use environmental cues to detect and respond to air currents and wind direction to find their food sources, according to van Breugel. In the presence of wind, those cues trigger an automatic “cast and surge” behavior, in which the fly surges into the wind after encountering a chemical plume (indicating food) and then casts — moves side to side — when it loses the scent. Cast-and-surge behavior long has been understood by scientists but, according to van Breugel, it was fundamentally unknown how insects searched for a scent in still air.

Through their work, van Breugel and Stupski uncovered another automatic behavior, sink and circle, which involves lowering altitude and repetitive, rapid turns in a consistent direction. Flies perform this innate movement consistently and repetitively, even more so than cast-and-surge behavior.

According to van Breugel, the most exciting aspect of this discovery is that it shows flying flies are clearly able to assess the conditions of the wind—its presence, and direction—before deploying a strategy that works well under these conditions. The fact that they can do this is actually quite surprising—can you tell if there is a gentle breeze if you stick your head out of the window of a moving car? Flies aren’t just reacting to an odor with the same preprogrammed response every time like a simple robot, they are responding in context-appropriate manner. This knowledge potentially could be applied to train more sophisticated algorithms for scent-detecting drones to find the source of chemical leaks.

So, the next time you try to swat a fly in your home, consider the fact that flies might actually be a little more aware of some of their natural surroundings than you are. And maybe just open a window to let it out.

 

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JOURNAL

Current Biology

DOI

10.1016/j.cub.2024.07.009 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

New understanding of fly behavior has potential application in robotics, public safety

ARTICLE PUBLICATION DATE

26-Jul-2024

Climate is most important factor in where mammals choose to live, study finds

WE ARE MAMMALS

NORTH CAROLINA STATE UNIVERSITY

While human activity has had a massive effect on the natural world, a new study from North Carolina State University finds that climate is still the most influential factor in determining where mammals can thrive. The work sheds light on how climate change will affect wildlife populations.

Roland Kays, lead author of a paper on the work, said the study’s goal was to compare the importance of climate versus human factors in where mammals chose to live. To do so, researchers collected data on 25 mammal species from 6,645 locations across the United States. The study is one of the largest camera trap data analyses ever done. The data came largely from Snapshot USA, which is a national mammal camera trap survey conducted with collaborators across the country.

“One of our ideas was that humans may have changed our landscape so much that we have become the primary determinants of which animals live where,” said Kays, who is a research professor at NC State and scientist at the N.C. Museum of Natural Sciences. “What we found was that in fact humans were not the most important. Climate, including temperature and the amount of rainfall, was the most important factor across most of the species we observed.”

However, human activity in the form of large population centers and agriculture was still a significant factor in where mammals chose to live. Some species struggled in the presence of cities and farms, Kays said, but many thrived.

“There are a lot of species that do well when humans are around. The Eastern gray squirrel for instance is the most common squirrel in Raleigh, and it does great around people. But there’s another species called the Eastern fox squirrel, and that one does well around agriculture but not as well around people,” he said. “We can see those differences in many other species. The snowshoe hare does poorly around both people and around agriculture. This study allows us to see the species that are sensitive to our impacts, and which ones benefit.”

This information helped researchers create maps which predict how common various mammals are across the contiguous U.S., which allowed them to separate the country into regions based on what kinds of mammals were common in each. These regions, known as ecoregions, are commonly used when studying plants but have never before been applied to mammal populations.

“When you look at something like the Eastern deciduous forest, that is an ecoregion classified by how common a type of tree is,” Kays said. “We’re now able to do that with mammal species and then compare that to the plant ecoregions. What we found was a striking similarity between the two. For instance, in the east where there is more rainfall, you have more plants growing. That lined up with a greater abundance of mammals that we saw in that region as well, because more plants mean more food for those animals to eat.”

The open access paper, “Climate, food and humans predict communities of mammals in the United States” is available to read in Diversity and Distributions. In identifying climate as the number one influence on mammal habitat choice, the study presents a new tool for predicting the impacts of climate change on mammal populations. Rising global temperatures will cause shifts in where animals are able to live, as well as influence precipitation levels and plant growth. Understanding these factors will be important to making sustainable decisions about mammal population management in the future.

-pitchford-

Note to Editors: The study abstract follows.

“Climate, food and humans predict communities of mammals in the United States”

Authors: Kays, R., Snider, M. H., Hess, G., Cove, M. V., Jensen, A., Shamon, H., McShea, W. J., Rooney, B., Allen, M. L., Pekins, C. E., Wilmers, C. C., Pendergast, M. E., Green, A. M., Suraci, J., Leslie, M. S., Nasrallah, S., Farkas, D., Jordan, M., Grigione, M., Parsons, A.

Published: June 27, 2024

DOI: 10.1111/ddi.13900

Abstract:

The assembly of species into communities and ecoregions is the result of interacting factors that affect plant and animal distribution and abundance at biogeographic scales. Here, we empirically derive ecoregions for mammals to test whether human disturbance has become more important than climate and habitat resources in structuring communities.

We analyzed data from 25 mammal species recorded by camera traps at 6645 locations across the conterminous United States in a joint modelling framework to estimate relative abundance of each species. We then used a clustering analysis to describe 8 broad and 16 narrow mammal communities.

Climate was the most important predictor of mammal abundance overall, while human population density and agriculture were less important, with mixed effects across species. Seed production by forests also predicted mammal abundance, especially hard-mast tree species. The mammal community maps are similar to those of plants, with an east–west split driven by different dominant species of deer and squirrels. Communities vary along gradients of temperature in the east and precipitation in the west. Most fine-scale mammal community boundaries aligned with established plant ecoregions and were distinguished by the presence of regional specialists or shifts in relative abundance of widespread species. Maps of potential ecosystem services provided by these communities suggest high herbivory in the Rocky Mountains and eastern forests, high invertebrate predation in the subtropical south and greater predation pressure on large vertebrates in the west.

Our results highlight the importance of climate to modern mammals and suggest that climate change will have strong impacts on these communities. Our new empirical approach to recognizing ecoregions has potential to be applied to expanded communities of mammals or other taxa.

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JOURNAL

Diversity and Distributions

DOI

10.1111/ddi.13900 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Climate, food and humans predict communities of mammals in the United States