Tuesday, July 29, 2025

Genome sequencing of butterflies resolves centuries-old conundrum

Florida Museum of Natural History

image:
A new study tracks the recent and rapid diversification of glasswing butterflies, which evolved within the last two million years in the tropics of South America.
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Credit: Florida Museum photo by Keith Willmott

When conditions are just right, organisms can undergo rapid bursts of diversification, and what starts out as one species can end up as an entire family tree in the evolutionary equivalent of the blink of an eye.

A new study published in the journal Proceedings of the National Academy of Sciences shows this is what recently happened to a group of tropical South American butterflies called glasswings, which partially explains why they all tend to look alike and why scientists have historically had such a hard time telling them apart.

“These butterflies have puzzled and exasperated lepidopterists, taxonomists and museum curators for centuries, including me personally for the last three decades,” said study co-author Keith Willmott, a curator at the Florida Museum’s McGuire Center for Lepidoptera and Biodiversity. “Apparently these species have evolved very recently and hybridized frequently.”

Rapid diversification events can be a headache for the scientists who study them. With so much happening all at once, it can be difficult or impossible for scientists to look back and figure out how everything was connected and which order events took place in.

In the case of glasswing butterflies, dozens of new species evolved within just the span of 1-2 million years, coinciding with drastic changes in climate that occurred during the Pleistocene ice ages. There were as many as 17 periods of intense cold and glaciation during the Pleistocene interspersed with prolonged stretches of balmy weather.

These chaotic shifts in climate resulted in the diversification of several different groups. Florida scrub mints, for example, were separated and later reunited several times as the state alternately flooded when sea levels rose and resurfaced when they sank. Scrub mints were isolated on islands when the waters were high, during which time many evolved into new species. When the waters were low, scrub mints expanded their distributions until they overlapped, resulting in widespread hybridization.

The same pattern seems to have played out in glasswing butterflies, only instead of being separated by an ocean, they may have become isolated in patches of forest or on opposite sides of the Andes as changes in rainfall and temperature disrupted their habitats. In other cases, closely related species with similar distributions show a preference for different elevations that now keep them separate.

The authors discovered this by sequencing the genomes of almost all species of two particularly fast radiations of glasswing butterflies to remap their evolutionary trees. Of those species, 10 were sequenced to the gold standard of “reference quality” genomes that are freely available to the research community.

By genetically mapping these butterflies, the team found that six geographic populations were more genetically distinct than previously thought, leading to them being recognized as new species. Also, understanding the species from a genomic perspective enables experts to highlight any visual differences that could be used to identify and track the different species, now that they are confirmed as genetically distinct.

“With this new genetically informed evolutionary tree, and multiple new reference genomes, we hope that it will be possible to advance biodiversity and conservation research around the world and help protect the butterflies and other insects that are crucial to many of Earth’s ecosystems,” said first author Eva van der Heijden, a doctoral student at the University of Cambridge.

Glasswings also played fast and loose with the number and arrangement of their chromosomes. These variations likely fanned the flames of diversification, since any two butterflies with different chromosome configurations would not have been able to produce viable offspring. These sorts of chromosome rearrangements have the potential to produce new species more or less instantaneously.

Rapid radiations tend to produce species that all look very similar as well, which is one of the reasons scientists have had such a hard time classifying glasswings. Species in this group also form complex mimicry rings, which means they look even more similar than they otherwise would.

But the butterflies themselves have a surefire way of recognizing each other.

“Chemical communication is likely to be especially important in butterflies that mimic each other, like glasswings, where recognizing members of the same species based on wing patterns is presumably more challenging,” Willmott said.

Glasswing butterflies feed on certain flowers and withered plants that contain a type of bitter alkaloid that birds find distasteful. They take advantage of this by storing as much of it as they can in their bodies. Birds quickly learn from trial and error which butterflies to associate with the toxin and leave them alone. Different species can reduce their losses by all sharing the same warning color pattern, a natural phenomenon called Müllerian mimicry, so that fewer individuals are attacked as predators learn what to avoid – once a bird learns one species, it will avoid them all.

But the alkaloids can also be used to make highly aromatic compounds, and glasswings have evolved a specialized organ to diffuse the scent.

“A defining feature of these butterflies is the presence of a ‘hair-pencil’ on the male hindwing, which resembles a paint-brush and is composed of highly elongate wing scales that disperse scents,” Willmott said.

The authors conducted an analysis of the perfume from three closely related species and found that all of them had distinct chemical profiles. Moths and butterflies, in general, have a keen sense of smell. Indian moon moths, for example, can follow the pheromone trail of a female from several miles away. It’s likely that glasswings rely on their distinct chemical calling cards rather than trying to visually identify potential mates in a sea of similar-looking butterflies.

Additional co-authors of the study are: Karin Näsvall, Patricio Salazar-Carrión, Jonah Walker, Nicol Rueda-M, Dominic Absolon, Thomas Mathers, Camilla Santos, Shane McCarthy, Jonathan Wood, Joana Meier and Marianne Elias of the Wellcome Sanger Institute; Fernando Seixas of Harvard University; Carlos Eduardo Beserra Nobre and Artur Campos Maia of the Federal University of Pernambuco; Daiane Szczerbowski and Stefan Schulz of the Technische Universität Braunschweig; Ian Warren and Chris Jiggins of the University of Cambridge; Kimberly Gabriela Gavilanes Córdova, María José Sánchez-Carvajal, Franz Chandi, Alex Arias-Cruz and Caroline Bacquet of the Universidad Regional Amazónica Ikiam; Camilo Salazar of the Universidad del Rosario, Bogotá; Kanchon Dasmahapatra of the University of York; Stephen Montgomery of the University of Bristol; Melanie McClure of the Université de Guyane; Gerardo Lamas of the Universidad Nacional Mayor de San Marcos; and André Victor Lucci Freitas of the Universidade Estadual de Campinas.

Male glasswing butterflies obtain bitter alkaloids from the plants they eat, then use it to create an aromatic fragrance to attract mates. Females get their fragrance strictly from males, so there’s a strong incentive to find one that’s particularly smelly.

Credit

Florida Museum photo by Keith Willmott.

Journal

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2410939122

Article Title

Genomics of Neotropical biodiversity indicators: Two butterfly radiations with rampant chromosomal rearrangements and hybridization

Article Publication Date

28-Jul-2025

U-M study: E-cigarettes could unravel decades of tobacco control

New research finds that UK teens who vape are 33% more likely to smoke cigarettes

University of Michigan

Teens who regularly use e-cigarettes are equally as likely as their peers from the 1970s to take up cigarette smoking, despite a substantial reduction in the prevalence of teenage cigarette use over the last 50 years, according to a study co-led by the University of Michigan.

U-M researchers, in collaboration with Penn State University and Purdue University, concluded that teenagers who had never used e-cigarettes had an approximately less than 1 in 50 chance of weekly cigarette use, whereas those who had previously used e-cigarettes had more than a 1 in 10 chance. More importantly, teenagers who reported consistent e-cigarette use had nearly a 1 in 3 chance of also reporting current conventional cigarette use.

The study illustrates shifts in the likelihood of youth cigarette use over time and the impacts of e-cigarettes on this trend. The results were derived from three longitudinal studies collected by the Centre for Longitudinal Studies at the University College of London, following teens from three different U.K. birth cohorts.

The research was published in the journal Tobacco Control and was supported by the National Cancer Institute, part of the National Institutes of Health, and a seed grant from the Criminal Justice Research Center at Penn State University, while data collection by the Centre for Longitudinal Studies was supported by funding from the Economic and Social Research Council.

"The use of e-cigarettes and the proliferation of e-cigarettes have really disrupted those awesome trends and improvements. For kids who have never used e-cigarettes, we do see those historic declines in risk," said Jessica Mongilio, a research fellow at the U-M School of Nursing and one of the lead researchers on the study. "But for kids who do use e-cigarettes, it's almost as if all of those policies and all of those perceptions have done nothing, and they've got a really high risk of smoking cigarettes."

Over the past few decades, cigarette smoking has evolved from a once glamorous status symbol to an unhealthy and socially discouraged practice, according to the researchers. This evolution was, in large part, driven by aggressive campaigning that labeled cigarette smoking as a public health risk.

By the late 1990s and into the early 2000s, cigarette smoking was structurally and socially stigmatized, embedded in national federal regulations and health policy. In recent years, cigarette smoking in youths dropped to an all-time low, according to research from the Centers for Disease Control.

E-cigarettes, colloquially known as vapes, often sold in bright colorways and in fruity flavors, have quickly emerged as a perceived "safer" alternative to the conventional cigarette. They stand to threaten decades of advocacy, health policy and cultural aversion toward smoking in both the U.K. and United States, the researchers say.

The Millennium Cohort Study, or MCS, tracked teens born in England, Scotland, Wales and Northern Ireland in 2000 and 2001 and who were children when e-cigarettes were first commercialized. The British Cohort Study tracked individuals born in 1970, who were teenagers during the 1980s when cigarette use was fairly common and in their 40s when e-cigarettes were commercially available. Finally, the National Child Development Study tracked individuals born in 1958, who were young children when cigarette use was at its cultural peak.

"We took data from different cohorts, essentially different generations of people who live in the U.K., and looked at their probability of smoking cigarettes at least once a week, based on some well-known risk and protective factors," Mongilio said. "For the most recent cohort, we also examined how use of e-cigarettes changed those probabilities.”

According to Mongilio and her collaborators, it's not entirely clear whether e-cigarette use directly caused cigarette use, but it’s clear their incidences are strongly related. Still, the MCS cohort will be continuously surveyed over time to further understand how the use of e-cigarettes during the critical developmental teen years will affect their health in the long term.

Ultimately, with the findings of this study, the researchers hope to demonstrate the profound impact of e-cigarettes on today's youth in an attempt to exact meaningful legislative, social and economic change.

"The more you can build evidence—the bigger the pile of support—the harder you can make it to ignore. This will lead toward policy changes and toward increased regulations for e-cigarettes and for producers of e-cigarettes," Mongilio said. "I think we're in a place where change is possible and to have increased regulations and enforcement of those regulations for companies that are producing e-cigarettes."

Study: Risk of adolescent cigarette use in three UK birth cohorts, before and after e-cigarette (DOI: doi:10.1136/tc-2024-059212)

Story written by Sarah Akaaboune, Michigan News

Journal

Tobacco Control

DOI

10.1136/tc-2024-059212

UK teens who currently vape as likely to start smoking as their peers in the 1970s

Likelihood of smoking 1.5% among teens who don’t vape, but 33% among those who do

BMJ Group

UK teens who currently vape are as likely to take up smoking as their peers in the 1970s, despite a substantial fall in the prevalence of teenage smoking over the past 50 years, suggests a long term intergenerational study published online in the journal Tobacco Control.

The likelihood of starting to smoke among teens who don’t vape was around 1.5%, but 33% among those who do, the findings indicate.

It’s not entirely clear if the rise in popularity of e-cigarettes (vapes) among teens threatens the steady decline in the prevalence of cigarette smoking in this age group, say the researchers, as the published research is somewhat equivocal.

And if historic declines are slowing, it’s not clear how the risk of cigarette smoking among today’s young people—especially those who vape—compares to that of previous generations who came of age before notable tobacco control legislation and the advent of e-cigarettes, they add.

To try and find out, they drew on intergenerational data from three nationally representative birth cohorts of UK teens* born in 1958 (National Child Development Study; NCDS), 1970 (The British Cohort Study; BCS), and 2001 (Millennium Cohort Study; MCS).

As well as baseline surveys at either birth or 9 months, MCS participants provided data at ages 3, 5, 7, 11, 14, 17 and 23; BCS participants at ages 5, 10, 16, 26, 30, 34, 38, 42, 46 and 51; and NCDS participants at ages 7, 11, 16, 23, 33, 42, 46, 50, 55 and 62.

The prevalence of teen smoking was assessed in 1974 among 11,969 NCDS participants, in 1986 among 6222 BCS participants, and in 2018 among 9733 MCS participants. The odds of smoking among 16 and 17 year olds were estimated, based on a common set of childhood risk and protective factors; teen vaping was included as a predictor in the MCS.

Risk/protective factors included whether they had ever drunk alcohol by age 16 or 17; how engaged they were with education at school; the extent of externalising behaviours reported by the mother or main caregiver at ages 10 or 11; and parental occupation, education, and smoking behaviour— including during pregnancy.

Analysis of the intergenerational data revealed a steep decline in the prevalence of cigarette smoking among teens, falling from 33% in 1974, to 25% in 1986, and to 12% in 2018. Around half of the MCS participants hadn’t vaped by the time they were 17; 41% said they had previously vaped; and 11% reported current vaping.

The decline in prevalence of teen smoking can be attributed to a mix of tobacco control legislation, better public understanding of the health consequences of smoking, and a shift away from the perception of smoking as socially acceptable, suggest the researchers.

Risk/protective factors also changed over time. For example, the percentage of teens who had started drinking by the age of 16 or 17 fell from 94% in the NCDS to 83% in the MCS.

The average age at which mothers left education also rose from 15.5 in the NCDS to 17 in the MCS. Similarly, the prevalence of parental smoking fell from over 70% in the NCDS to 27% in the MCS; and fewer mothers continued smoking while pregnant in the MCS than in the NCDS and the BCS.

Many risk factors for teen smoking were similar across the cohorts—drinking before the age of 17 and greater externalising behaviours, for example—as were some child level protective factors—greater engagement with education, for example.

To illustrate the likelihood of cigarette smoking for an ‘average’ teen (16-17) over time, the researchers worked out predicted probabilities of cigarette smoking with all risk factors included from the intergenerational data.

This probability was 30% in the NCDS and 22% in the BCS. Among those who had never vaped in the MCS this was around 1.5%, but 33% for the teens who reported current vaping.

“This probability is especially concerning given the recent increases in e-cigarette use prevalence among UK youth, despite some initial assurances that e-cigarettes would have little appeal to [them],” say the researchers.

The researchers acknowledge that they were unable to account for some sociodemographic characteristics, including race and ethnicity, due to insufficient sample sizes in the earlier cohorts. And they emphasise that estimates of the associations between vaping and smoking in the MCS aren’t causal and shouldn’t be interpreted as such, especially as the temporal sequencing of smoking and vaping isn’t explicit.

Nevertheless they conclude: “While our research shows that the historic decline in the likelihood of youth cigarette smoking has continued in this recent cohort of UK youth, overall, we find that this is not the case among e-cigarette users.

“Youth who had never used e-cigarettes had an estimated less than 1 in 50 chance of reporting weekly cigarette use at age 17, while those who had previously used e-cigarettes had over a 1 in 10 chance. Youth who reported current e-cigarette use had an almost 1 in 3 chance of also reporting current cigarette use.

“As such, the decline in the likelihood of cigarette smoking is waning for youth who have used e-cigarettes—about half of our sample—and has reversed for those currently using e-cigarettes.

“Among contemporary youth, efforts to reduce cigarette smoking should focus both on those who are currently using e-cigarettes and on the prevention of e-cigarette use among youth, to maintain the promising declines in youth nicotine use in years to come.”

Journal

Tobacco Control

DOI

10.1136/tc-2024-059212

Method of Research

Observational study

Subject of Research

People

Article Title

Risk of adolescent cigarette use in three UK birth cohorts before and after e-cigarettes

Article Publication Date

29-Jul-2025

Blending technologies may help coral offspring blossom

Artificial settlements, underwater lights doubled survival

Ohio State University

COLUMBUS, Ohio – Coral restoration efforts could be dramatically improved with technologies that support the survival and growth of baby corals, suggests a new study.

Findings showed that two novel devices, the Underwater Zooplankton Enhancement Light Array (UZELA) and 3D printed artificial settlement modules, could together boost the population of a species of coral native to Hawaii.

In a previous study led by researchers at The Ohio State University, scientists found that UZELA successfully attracted nearby zooplankton, microscopic organisms that coral feed on. That study found that the light greatly enhanced local zooplankton density and increased the feeding rates of adult coral. In this one, they found that combining the light with 3-D printed housing modules could double survivorship and quadruple the growth of baby corals, which are called recruits.

Coral reefs are vital drivers of the marine ecosystem. Yet as rising global temperatures and acidifying oceans threaten their food sources, many coral reefs are now experiencing severe population declines. Typically, these losses would be recovered slowly via a process called coral recruitment, where adult coral colonies reproduce by releasing small larvae to recolonize the reef.

But juvenile corals often die before they can become larger colonies, creating a population bottleneck that nature can’t always overcome alone, said Shannon Dixon, lead author of the study and a graduate student in earth sciences at Ohio State.

“Coral recruitment is super important for reef persistence throughout time,” she said. “Just like how trees drop seeds to create new trees, the life cycle of coral is very similar.”

While this process also acts as a way for coral to cope with environmentally stressful events like heat stress or cyclones, some reefs, like the Florida Keys, experience little to no coral recruitment, so human intervention is needed to ensure the reef continues to thrive, said Dixon.

Now, as the first team to exhibit a combined technology method for coral recovery, the researchers in this study reveal that the presence of UZELA and the complex settlement modules could reduce the time coral need to complete this vulnerable “baby” phase of their lives, while accelerating the timeline for establishing genetically diverse coral populations. More importantly, by exposing coral recruits to higher concentrations of zooplankton, these tools worked to double coral survivorship and quadruple their growth.

“Making reefs more habitable for coral recruits is extremely important,” said Dixon. “If we can create the ideal living conditions for struggling coral reefs, we’ll see more survivorship, higher biodiversity, and more reefs in geographical locations than we would see without these tools.”

The study was recently published in the journal Environmental Science & Technology.

On the quest to help coral offspring survive a harrowing early life, scientists used UZELA in tandem with three types of artificial ceramic settlement modules.

Of the 30 modules used in this experiment, 10 had flat surfaces, 10 were smooth domes, and 10 were spiral domes. Half of the modules of each type were coupled with UZELA to concentrate zooplankton, while the other half did not have UZELA as a control. Researchers had theorized that certain domes would be better for the survival and growth of the coral because of their complexity, which turned out to be true.

After six months on the reef, no corals on the flat surface survived, but some had on both the smooth and spiral domes. However, those that grew with UZELA on the smooth and spiral dome settlement modules survived at twice the rate of those that didn’t have UZELA.

Unsurprisingly, these findings are consistent with the idea that coral larvae tend to avoid horizontal surfaces, preferring to settle in a structure’s minute crevices, said Dixon.

At the end of the experiment, all surviving coral recruits appeared healthy, suggesting the tools this team used are extremely adept at improving coral feeding. This result is great news during a time when global coral mortality is reaching record highs, said Andrea Grottoli, senior co-author of the study and a professor in earth sciences at Ohio State, but it is especially meaningful for baby corals, as they usually require lots of high-quality nutrition to prosper.

“This outcome is directly applicable to what we might expect survivorship and growth to look like on other reefs using these technologies,” she said. “It just goes to show how a little goes a long way when you give coral a little more to eat.”

UZELA is currently patent pending in three countries, including the United States. This work illustrates how effectively the project could be scaled up for use in active coral restoration programs, potentially making both local and worldwide conservation efforts faster and far more effective. But there’s only so much that man-made gadgets can do for the coral community, said Grottoli.

“Technological interventions like UZELA and the settlement modules will help some corals survive in some places, sometimes,” she said. “But with all technologies, there are real costs and real efforts associated with them.”

One of the most important keys to bridging the current coral survivorship gap may be to determine the impact this study’s devices will have on multiyear coral recruit survivorship, maturation and reproduction, which the team plans to investigate.

“This project highlights how wonderfully you can combine technological interventions that you didn’t necessarily see fitting together, but push the envelope to solve problems in new multidisciplinary ways,” said Dixon. “Research like this allows us to embrace the collaborative nature of science to make the environment better for coral.”

Co-authors include Ann Marie Hulver and Jacob Welter from Ohio State, Hendrikje Jorissen, Robert J. Toonen, and Joshua S. Madin from the University of Hawaiʻi, and the R3D Consortium. This work was supported by the University of Hawaiʻi Foundation, the National Science Foundation and the Defense Advanced Research Projects Agency.

Contact: Andrea Grottoli, Grottoli.1@osu.edu

Written by: Tatyana Woodall, Woodall.52@osu.edu

Journal

Environmental Science & Technology

Article Title

Technology Solutions for Overcoming the Coral Recruitment BottleneckClick to copy article link

Article Publication Date

29-Jul-2025

UBC-led international team proposes global framework to tackle toxic tire pollution crisis

Call for urgent action on unregulated tire chemicals linked to fish deaths and potential human health risks

University of British Columbia

Surveying ponds and streams — image:
UBC researchers are surveying ponds, creeks and streams across the Lower Mainland in B.C. in hopes of building future rain gardens and other “green infrastructure” that can contain toxic chemicals shed by car tires. Photo credit: Dr. Timothy Rodgers
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Credit: Photo credit: Dr. Timothy Rodgers

An international research team led by the University of British Columbia has proposed the first comprehensive global framework for regulating tire additives, linked to mass fish die-offs and detected in humans. These chemicals are a ubiquitous yet largely unregulated source of environmental contamination affecting ecosystems and human health worldwide.

Published today in Environmental Science & Technology Letters, the article outlines the Management Framework for Tire Additive Pollution, a proactive policy roadmap inspired in part by the successful Montreal Protocol, which helped reverse ozone layer damage. With the next round of global plastics treaty negotiations (INC-5.2) beginning August 5 in Geneva, the researchers say the time is now to put tire additives on the international regulatory agenda.

“These chemicals are everywhere—urban streams, sediments, even Arctic environments—and they’re now showing up in people,” said Dr. Timothy Rodgers, lead researcher and postdoctoral fellow in the Scholes Lab at UBC’s department of civil engineering in the faculty of applied science. “Yet tire additives haven’t received the regulatory attention that other pollutants like pesticides or industrial chemicals have. It’s a major blind spot.”

One such chemical, 6PPD-quinone, is formed when the tire preservative 6PPD reacts with ozone. It has been linked to mass die-offs of coho salmon and has been detected in human biomonitoring samples, including urine and cerebrospinal fluid. As tires wear down, they release particles and additives into the environment at massive scales—estimated at over one million tonnes annually in both the U.S. and E.U.

Five-point action plan for safer, more transparent regulation

The proposed framework outlines five key action areas:

A phased transition towards safe, non-hazardous tire additives
Consideration of tire impacts throughout their life cycle
Greater transparency on the chemicals used in tires and their properties
Independent assessments on the hazards of tire additives and their replacements
International coordination, potentially through the proposed global plastics treaty

The paper also highlights how Indigenous communities and vulnerable populations bear disproportionate exposure risks. For instance, the Tseshaht First Nation in B.C. has witnessed dramatic salmon population declines potentially tied to road runoff on their lands.

"This is an issue of environmental justice and health," added Dr. Rodgers. "Communities that depend on healthy ecosystems are already paying the price, and we don't know the health effects for all the people being exposed."

Setting the stage for global change

The research team, comprising researchers from 12 institutions across four countries, hopes the framework will inform policy decisions and regulatory approaches worldwide, providing a roadmap for addressing this overlooked environmental crisis before its impacts become irreversible.

“We have a chance to get ahead of this issue before it becomes even more entrenched,” said Dr. Rachel Scholes. “This framework gives regulators a clear path forward—and a critical opportunity to protect both ecological and human health on a global scale.”

UBC researchers are surveying ponds, creeks and streams across the Lower Mainland in B.C. in hopes of building future rain gardens and other “green infrastructure” that can contain toxic chemicals shed by car tires.