It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
IMAGE: WITH MOUTHS CLOSED, THE OLDER, SMALLER TEETH OF THE ANCESTORS OF TODAY'S SHARKS STOOD UPRIGHT ON THE JAW, WHILE THE YOUNGER AND LARGER TEETH POINTED TOWARDS THE TONGUE AND WERE... view more
CREDIT: ILLUSTRATION: CHRISTIAN KLUG, UZH
Some, if not all, early sharks that lived 300 to 400 million years ago not only dropped their lower jaws downward but rotated them outwards when opening their mouths. This enabled them to make the best of their largest, sharpest and inward-facing teeth when catching prey, paleontologists at the Universities of Zurich and Chicago have now shown using CT scanning and 3D printing.
Many modern sharks have row upon row of formidable sharp teeth that constantly regrow and can easily be seen if their mouths are just slightly opened. But this was not always the case. The teeth in the ancestors of today's cartilaginous fish (chondrichthyan), which include sharks, rays and chimaeras, were replaced more slowly. With mouths closed, the older, smaller and worn out teeth of sharks stood upright on the jaw, while the younger and larger teeth pointed towards the tongue and were thus invisible when the mouth was closed.
Jaw reconstruction thanks to computed tomography
Paleontologists at the University of Zurich, the University of Chicago and the Naturalis Biodiversity Center in Leiden (Netherlands) have now examined the structure and function of this peculiar jaw construction based on a 370-million-year-old chondrichthyan from Morocco. Using computed tomography scans, the researchers were able not only to reconstruct the jaw, but also print it out as a 3D model. This enabled them to simulate and test the jaw's mechanics.
What they discovered in the process was that unlike in humans, the two sides of the lower jaw were not fused in the middle. This enabled the animals to not only drop the jaw halves downward but at the same automatically rotate both outwards. "Through this rotation, the younger, larger and sharper teeth, which usually pointed toward the inside of the mouth, were brought into an upright position. This made it easier for animals to impale their prey," explains first author Linda Frey. "Through an inward rotation, the teeth then pushed the prey deeper into the buccal space when the jaws closed."
Jaw joint widespread in the Paleozoic era
This mechanism not only made sure the larger, inward-facing teeth were used, but also enabled the animals to engage in what is known as suction-feeding. "In combination with the outward movement, the opening of the jaws causes sea water to rush into the oral cavity, while closing them results in a mechanical pull that entraps and immobilizes the prey."
Since cartilaginous skeletons are barely mineralized and generally not that well preserved as fossils, this jaw construction has evaded researchers for a long time. "The excellently preserved fossil we've examined is a unique specimen," says UZH paleontologist and last author Christian Klug. He and his team believe that the described type of jaw joint played an important role in the Paleozoic era. With increasingly frequent tooth replacement, however, it became obsolete over time and was replaced by the often peculiar and more complex jaws of modern-day sharks and rays.
Cichlid fishes from African Lake Tanganyika shed light on how organismal diversity arises
IMAGE: OPHTHALMOTILAPIA VENTRALIS, A CICHLID FROM LAKE TANGANYIKA. view more
CREDIT: PHOTO: ADRIAN INDERMAUR, UNIVERSITY OF BASEL/ZOOLOGY
Lake Tanganyika in Africa is a true hotspot of organismal diversity. Approximately 240 species of cichlid fishes have evolved in this lake in less than 10 million years. A research team from the University of Basel has investigated this phenomenon of "explosive speciation" and provides new insights into the origins of biological diversity, as they report in the journal Nature.
The diversity of life on Earth has been shaped by two antagonistic processes: phases of mass extinctions and episodes characterized by the rapid evolution of a multitude of new species. Such outbursts of organismal diversity, also known as "adaptive radiations", are responsible for a substantial part of the biological species on our planet.
For instance, most of the animal phyla existing today evolved over the course of the Cambrian radiation about 540 million years ago (also known as Cambrian explosion). What triggered these massive adaptive radiations, and how the process of explosive speciation proceeds in detail, has been largely unknown until now.
Different stages of adaptive radiation
The cichlid fishes of the African Great Lakes Victoria, Malawi and Tanganyika are among the most impressive examples of "adaptive radiation". Using the cichlid fishes of Lake Tanganyika as a model system, a team of scientists headed by Professor Walter Salzburger from the University of Basel have now investigated in detail the phenomenon of adaptive radiation. On extensive field expeditions to Burundi, Tanzania and Zambia, they collected specimens from virtually all approximately 240 species of cichlid fishes occurring in Lake Tanganyika.
Based on this material, they compiled a comprehensive dataset covering information on morphology, ecology, and genetics. For example, the team analyzed body shape and jaw morphology of all species using X-ray imaging and high-resolution computed tomography. The zoologists were particularly interested in the three-dimensional structure of the pharyngeal jaw. This second set of jaws is situated in the pharynx of cichlid fishes and is used to masticate food, allowing the fish to specialize in very specific nutritional niches.
Because adaptation to different environments is a central component of adaptive radiation, the researchers also quantified the "ecological niche" used by each species. In collaboration with the Botanical Institute of the University of Basel, they measured the stable carbon and nitrogen isotope composition in the muscle tissue of the fish. These measurements allow to determine in what habitat the fishes lived and what food resources they used. Further, the team sequenced two complete genomes for each and every cichlid species from Lake Tanganyika. Based on this molecular information they were able to reconstruct the complete phylogeny of the cichlids in that lake.
Based on their analyses, the scientists could demonstrate that the evolution of cichlid fishes in Lake Tanganyika was not a gradual process, but rather occurred in three discrete pulse-like stages of rapid morphological evolution.
"Each of these stages was characterized by specialization to a different aspect of the habitat provided by the lake," says lead author Dr. Fabrizia Ronco. The first pulse involved diversification in body shape followed by a pulse in mouth morphology and a final pulse in pharyngeal jaw shape. Especially the pharyngeal jaw has played a key role in the radiation, since its rapid morphological evolution coincided with a high number of speciation events.
Insight into the evolution of organismal diversity
Through the analysis of the roughly 600 newly sequenced genomes, the Basel researchers showed that the most species-rich and ecologically and morphologically diverse lineages of Tanganyikan cichlids contain species that are genetically more diverse. "Whether an elevated level of genetic diversity is a general feature of highly diverse lineages, or if this pattern is unique to cichlids of Lake Tanganyika, is still unknown," says Salzburger.
By studying exceptionally species-rich adaptive radiations, like the African cichlids, scientist can learn more about how biodiversity arises and what factors are associated with it. The present findings of the zoologists from the University of Basel offer new routes to these questions.
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How fishermen have adapted to change over the past 35+ years
IMAGE: AN ANALYSIS PUBLISHED IN FISH AND FISHERIES NOTES THAT MARINE FISHERIES ARE INCREASINGLY EXPOSED TO EXTERNAL DRIVERS OF SOCIAL AND ECOLOGICAL CHANGE, AND RECENT CHANGES HAVE HAD DIFFERENT IMPACTS UPON... view more
CREDIT: AMERICAN ALBACORE FISHING ASSOCIATION
An analysis published in Fish and Fisheries notes that marine fisheries are increasingly exposed to external drivers of social and ecological change, and recent changes have had different impacts upon the livelihood strategies favored by fishermen based on the size of their boats.
The analysis describes changes among Pacific Northwest fishermen over 35+ years, with a focus on the albacore troll and pole-and-line fishery. In describing different trajectories associated with the albacore fishery, one of the U.S. West Coast's last open access fisheries, the authors highlight the diverse strategies used to sustain fishing livelihoods in the modern era. They argue that alternative approaches to management and licensing may be needed to maintain the viability of small-scale fishing operations worldwide.
"While resource managers have traditionally focused on maximizing economic returns one species at a time, new approaches that prioritize diversity and flexibility may be required to help coastal communities navigate the uncertainty associated with climate change and the globalization of seafood markets," said lead author Timothy H. Frawley, PhD, of NOAA Southwest Fisheries Science Center and the University of California Santa Cruz.
Vertebrate biodiversity- a glimmer of hope
Extreme losses in a few populations drive apparent global vertebrate decline
IMAGE: RED ASTERISKS NEAR A VERTEBRATE INDICATE CLUSTERS OF POPULATIONS OF SPECIFIC TYPES (AMPHIBIANS, SMALL MAMMALS, LARGE MAMMALS, FISH, BIRDS OR REPTILES) THAT ARE SUFFERING EXTREME DECLINES (16 SYSTEMS) BLUE ASTERISKS... view more
CREDIT: MCGILL UNIVERSITY
Vertebrate populations - from birds and fish to antelope - are not, in general, declining. Despite what has previously been thought and said.
A McGill University-led team of biologists found, in an article published today in Nature, that the picture of dramatically declining vertebrate populations of all kinds is driven by a small number of outlier populations whose numbers are dropping at extreme rates. Once these outliers are separated from the mix, a very different and far more hopeful picture of global biodiversity emerges.
(Populations are groups of individuals of the same species living in a particular area, and therefore decreases in population size will precede loss of species.)
Reports of my death are greatly exaggerated
It all comes down to math, modeling and different approaches to calculating averages.
It has typically been estimated that vertebrate populations have declined on average by more than 50% since 1970, based on historical wildlife monitoring data. "However, given previous mathematical methods used to model vertebrate populations, this estimate could arise from two very different scenarios: widespread systematic declines, or a few extreme declines," explains Brian Leung a McGill ecologist, the UNESCO Chair in Dialogues for Sustainability, and the senior author on the study. In this paper the researchers approached the question differently.
Using a dataset of over 14,000 vertebrate populations from around the globe collated in the Living Planet Database, the researchers identified about 1% of vertebrate populations which have suffered extreme population declines since 1970 (such as reptiles in tropical areas of North, Central and South America, and birds in the Indo-Pacific region). When this extreme 1% was accounted for, the researchers found the remaining vertebrate populations were neither generally increasing nor decreasing, when grouped all together.
"The variation in this global aggregate is also important. Some populations really are in trouble and regions such as the Indo-Pacific are showing widespread systematic declines. However, the image of a global 'biodiversity desert' is not supported by the evidence." says Leung. "This is good, as it would be very discouraging if all of our conservation efforts over the last five decades had little effect."
"We were surprised by how strong the effect of these extreme populations was in driving the previous estimate of average global decline," adds co-author Anna Hargreaves, a professor in the Biology Department at McGill. "Our results identify regions that need urgent action to ameliorate widespread biodiversity declines, but also reason to hope that our actions can make a difference."
CAPTION
Red asterisks near a vertebrate indicate clusters of populations of specific types (amphibians, small mammals, large mammals, fish, birds or reptiles) that are suffering extreme declines (16 systems). Blue asterisks indicate clusters of populations of specific types (amphibians, small mammals, large mammals, fish, birds or reptiles) that are growing significantly (8 systems). Distribution curves show the situation of typical populations in each system. After removal of extreme clusters of populations where there are significant increases or declines, the remaining populations are divided into: Yellow - indicates populations where there is little change. Green - indicates populations where, in general, the trend is towards a significant increase, though the data remains insufficient to conclude this with confidence. Orange - indicates populations where, in general, the trend is towards a significant decrease, though the data remains insufficient to conclude this with confidence.
Founded in Montreal, Quebec, in 1821, McGill University is Canada's top ranked medical doctoral university. McGill is consistently ranked as one of the top universities, both nationally and internationally. It is a world-renowned institution of higher learning with research activities spanning two campuses, 11 faculties, 13 professional schools, 300 programs of study and over 40,000 students, including more than 10,200 graduate students. McGill attracts students from over 150 countries around the world, its 12,800 international students making up 31% of the student body. Over half of McGill students claim a first language other than English, including approximately 19% of our students who say French is their mother tongue.
CAPTION
Red asterisks near a vertebrate indicate clusters of populations of specific types (amphibians, small mammals, large mammals, fish, birds or reptiles) that are suffering extreme declines (16 systems) Blue asterisks indicate clusters of populations of specific types (amphibians, small mammals, large mammals, fish, birds or reptiles) that are growing significantly (8 systems) After removal of extreme clusters of populations where there are significant increases or declines, the remaining populations are divided into: Yellow - indicates populations where there is little change. Green - indicates populations where, in general, the trend is towards a significant increase, though the data remains insufficient to conclude this with confidence. Orange - indicates populations where, in general, the trend is towards a significant decrease, though the data remains insufficient to conclude this with confidence. Distribution curves show the situation of typical populations in each system.
Iceland in 2010: The Eyjafjallajökull volcano erupts. Image: By anjči, via Wikimedia Commons
Skyseed: geo-engineering the planet might be humankind’s last desperate throw, says a tale by a geophysical hazard expert.
LONDON, 30 October, 2020 − There were always three objections to the technofix answer to climate change: that geo-engineeering wouldn’t work, that it would deliver unintended consequences that would be unpredictably distributed, and a third, rarely mentioned: that it might work all too well.
Skyseed has what good thrillers always need, as well as geo-engineering: a world to save, characters with a bit of go in them, some plausible villains, fast-paced action, sustained tension, a big moment of reckoning and (let us be honest) as little preaching as possible.
The story is a simple one of global eco-collapse. Volcanoes are involved, and extreme weather, and ice, but not the outcome that McGuire (a volcanologist who for many years headed research into natural hazards) has spent a working lifetime warning about.
In this book, instead of taking the obvious route and abandoning fossil fuels as an energy source, a bullying, dishonest and unthinking American president, dependent on what is now called “dark money”, with help from a fawning British prime minister sorely in need of a trade deal, decides to contain global heating in a different way.
“The precise manner in this book in which civilisation perishes as a consequence of climate change is fortunately so far implausible”
The duo authorise a dangerous experiment in geo-engineering, under the cover of some so-called rain-making experiments during high-altitude military flights. That’s mistake one.
Mistake two is that they do it secretly. And they seem to think that a small army of global climate scientists − people whose career is based on sampling the stratospheric atmosphere and matching its chemistry with global temperature levels − won’t notice. And that if they do, these academic busybodies can be rubbed out without anyone else asking awkward questions.
Of course, things go wrong: horribly wrong, and it doesn’t take long for a trio of all-too human scientists, working separately and together, to tumble to the truth. As soon as they start to do so, sinister forces try to contain the secret. Our heroes survive, thanks to fortune, subterfuge and some help with the weather, and come back with the truth: don’t mess with geo-engineering.
In the course of this entertainment, the informed reader could play the game of spot-the-science: quite a lot, actually, but trailed racily and with just enough explanation to keep the story at stampede speed − advanced nano-engineering, upper atmosphere chemistry, volcanic discharges, the interplay of climate change on geological hazard, the advance of an ice front, and so on. You could both enjoy the story and learn a little more about how the planet works.
Not escapist
McGuire poses no great threat to the reputations of Len Deighton, Leslie Charteris and Ian Fleming, but who cares? Their heroes always survived, to begin a new adventure in each successive volume.
In Skyseed, whoever makes it to the last page doesn’t expect to survive for much longer, and − non-spoiler alert − McGuire cheerfully breaks that bit of bad news to the reader in the prologue. You know this one is going to end badly, before it even begins.
A declaration of interest: I know McGuire, professionally, and have done for many years. Another declaration: I can think of less readable books, by vastly better-known popular authors. And a third: the precise manner in this book in which civilisation perishes as a consequence of climate change is fortunately so far implausible.
That civilisation is threatened, and all too plausibly, by the inexorable increase of carbon dioxide in the atmosphere, unhappily is not. You could call this book a thriller. You could not call it escapist. − Climate News Network
IMAGE: OHIO STATE UNIVERSITY SCIENTISTS OBSERVED TREE SWALLOWS AS A MODEL SPECIES IN A STUDY ON THE EFFECTS OF URBANIZATION THAT FOUND CITY LIVING MAY OFFER WILDLIFE SOME ADVANTAGES, BUT NOT... view more
CREDIT: JOSEPH CORRA, OHIO STATE UNIVERSITY
COLUMBUS, Ohio - City living appears to improve reproductive success for migratory tree swallows compared to breeding in more environmentally protected areas, a new five-year study suggests. But urban life comes with a big trade-off - health hazards linked to poorer water quality.
Researchers found that city-dwelling birds bred more nestlings because of warmer local temperatures. But they also had much higher levels of mercury in their blood - presumably from eating insects that spent their larval stages in contaminated water - than their counterparts breeding in less urban areas.
The study was conducted in central Ohio, where scientists observed tree swallows as a model species to assess their breeding success, diet and health measures in the context of varied temperatures, water quality and land use based on the location of their nests.
Despite those specifics, Ohio State University researchers consider the long-term study a harbinger of what's to come for all sorts of wildlife as urbanization increases while the climate continues to warm, and how land-use changes are likely to harm water quality and threaten biodiversity.
Urban land accounts for about 70 million acres in the contiguous United States, representing a 470% increase since 1945.
"With urbanization expanding worldwide, we are transforming the landscape. And this isn't going away," said lead author Ma�eika Sullivan, director of the Schiermeier Olentangy River Wetland Research Park at Ohio State. "My lab is looking at how urbanization affects multiple responses of ecosystems - what those changes are and quantifying them, but also seeing what this tells us about how we can manage and conserve ecosystems and wildlife in this context.
"Our task, knowing wildlife are using urban settings, is to think about ways to maximize benefits and minimize the risks. There's nature in cities. So how can we make our cities a little more wild?"
Sullivan, also an associate professor in Ohio State's School of Environment and Natural Resources, completed the work with graduate students Joseph Corra and Jeffry Hayes. The study was published online Nov. 15 in the journal Ecological Monographs.
Tree swallows are part of a guild of birds called aerial insectivores, which do all their dining on insects while in flight. Other species of swallows, as well as whip-poor-wills, nighthawks, swifts, martins and flycatchers, are also part of this group, and many of these species rely on ecosystems near water for food and habitat. Previous research has suggested that the number of North American birds has declined by about 3 billion since 1970, and the populations of some species of aerial insectivores have declined by over 50%.
The magnitude of that loss alone is a striking example of biodiversity loss, Sullivan said. But the reduction in this guild of birds can also affect the economy and the quality of human life.
"These migratory birds are really important not just in and of themselves, but because they're controlling insects - including pest insects that carry disease or damage agricultural crops. So they are very, very important in terms of how ecosystems function and stay in balance," he said.
For research purposes, tree swallows are also useful subjects because they are "cavity nesters" that flocked to the assortment of artificial nest boxes the team constructed along waterways in Columbus, some in developed zones and others in more forested areas.
From 2014-2018, the researchers observed tree swallows during their breeding season, most of May and June each year, also measuring their body weight and blood glucose and mercury levels and tracking how much of the birds' food source came from insects emerging from water or starting their pre-winged life on land. The scientists also monitored temperature and chemical water quality and quantified percentages of forested or wetland versus developed land at the breeding sites.
Egg-laying occurred significantly earlier (by almost eight days), the clutch sizes were larger, and the number of fledglings that left the nest was higher at the urban sites than at protected sites. This reproductive success was largely attributable to the temperature: The air was warmer in urban sites than in protected sites by an average of 3 degrees Fahrenheit, and city locations had fewer extremely cold days.
"We were looking at urbanization in two different ways - as a category of urban versus not urban, but also as gradients of urbanization. As the amount of urbanization increased, fledgling success increased," Sullivan said. "This tells us local climate is extremely important for reproductive success of tree swallows, and likely other insectivorous birds."
But that success came with potential health risks related to poorer water quality in urban areas. Insects that emerge from water constituted roughly a third of the tree swallows' diet, and those insects also tend to provide more nutrition and energy than terrestrial flying insects. But the river water in urban areas had higher levels of mercury - likely a proxy for other contaminants - and the adult birds' blood concentration of mercury was 482% higher in city-dwellers than in those who bred in protected sites.
"This is an important warning," Sullivan said. "There's a whole suite of environmental contaminants out there - pesticides, a lot of other heavy metals. So despite the advantage for breeding in these urban areas, there can be a trade-off in individual health."
These findings, and the implications for birds and other wildlife affected by growing urbanization, suggest that productive urban habitats should be factored in to future municipality planning, he said.
Some top considerations for insectivorous birds, as Sullivan sees it, would be establishing protected green ways, creating nesting habitats and structures to replace lost trees and other parts of the natural landscape, lowering the chances for contaminants to stream into waterways, and protecting wildlife food sources by reducing the use of pesticides and insecticides.
"If we had found that urbanization was negatively affecting tree swallows in all the different measures we used, that would be a very different story," Sullivan said. "But I see some rays of hope here."
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This work was supported by the National Science Foundation, the Ohio Department of Natural Resources, the Ohio Water Development Authority and Ohio State.
IMAGE: A STUDY PUBLISHED IN ECOLOGICAL APPLICATIONS SUGGESTS THAT NATURE AROUND ONE'S HOME MAY HELP MITIGATE SOME OF THE NEGATIVE MENTAL HEALTH EFFECTS OF THE COVID-19 PANDEMIC. view more
CREDIT: DR. SOGA
A study published in Ecological Applications suggests that nature around one's home may help mitigate some of the negative mental health effects of the COVID-19 pandemic.
An online questionnaire survey completed by 3,000 adults in in Tokyo, Japan, quantified the link between five mental-health outcomes (depression, life satisfaction, subjective happiness, self-esteem, and loneliness) and two measures of nature experiences (frequency of greenspace use and green view through windows from home).
More frequent greenspace use and the existence of green window views from the home were associated with increased levels of self-esteem, life satisfaction, and subjective happiness, as well as decreased levels of depression and loneliness.
"Our results suggest that nearby nature can serve as a buffer in decreasing the adverse impacts of a very stressful event on humans," said lead author Masashi Soga, PhD, of The University of Tokyo. "Protecting natural environments in urban areas is important not only for the conservation of biodiversity, but also for the protection of human health."
Trees and green roofs can help reduce the urban heat island effect, finds a new study
Air pollution experts from the University of Surrey have found that green infrastructure (GI), such as trees, can help reduce temperatures in many of Europe's cities and towns.
An urban heat island is an urban area that is significantly warmer than its surrounding rural areas. The temperature difference is typically larger at night than during the day.
With the UK government pledging to build 300,000 new homes every year, it is feared that many of the country's towns and cities will experience an increase in temperature brought about by more vehicles and building activity.
In a paper published by Environmental Pollution, experts from Surrey's Global Centre for Clean Air Research (GCARE) modelled how a UK town would be affected if its urban landscape included different types of GI.
The study focused on simulating temperature increases in the town of Guildford, UK, under different GI cover (trees, grassland and green roofs). The team adopted widely-used computer modelling systems that found that 78 per cent of Guildford was covered by grassland and trees.
The research team set out to investigate five scenarios:
What is the status quo with the current GI?
What would happen if the town had no GI?
What would happen if you replaced the current GI with only trees?
What would happen if you replaced the current GI with only green roofs?
What would happen if you replaced the current GI with only grassland?
The GCARE team found that trees are the most effective form of GI and the results showed that Guildford would be 0.128oC cooler if trees replaced all forms of GI in the town.
The team also found that trees are the best solution for the reduction in temperature spikes because they can better shade surfaces and influence aerodynamic mixing of air in the atmosphere caused by enhanced turbulence.
Professor Prashant Kumar, Director of GCARE at the University of Surrey, said: "As policymakers and political leaders rightly look to solve the nation's housing crisis, it is vitally important that they consider how this influx of new urban infrastructure will impact our environment and our planet.
"I hope that our study will give decision-makers the information they need when they are deciding which green infrastructure to establish in our communities. Our results suggest that, given a choice, trees are the most effective at reducing the urban heat island effect that many of our towns face."
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Note to editors
This work was supported by the H2020 iSCAPE project (Grant Agreement #689954) and the EPSRC INHALE project (EP/T003189/1). It builds upon previous GCARE research into proposed modelling methods for evaluating the impact of green infrastructure and the impact of GI on air pollutant dispersion at an urban scale under different GI scenarios, and nexus between green infrastructure, air pollution and human health.
Reference Tiwari, A., Kumar, P., Kalaiarasan, G., Ottosen, T.B., 2020. The impacts of existing and hypothetical green infrastructure scenarios on urban heat island formation. Environmental Pollution, 115898.
Research on environmental history: 330-year-old poplar tree tells of its life
IMAGE: USING TREES AS A MODEL, RESEARCHERS OF THE TUM AND OF THE UNIVERSITY OF GEORGIA, USA, HAVE SHOWN FOR THE FIRST TIME THAT EPIMUTATIONS ACCUMULATE CONTINUOUSLY THROUGHOUT PLANT DEVELOPMENT AND... view more
CREDIT: ROBERT SCHMITZ
Epigenetic marks do not change the DNA sequence but can affect the activity of genes. "Although in animals, including humans, these marks are believed to be completely reset in gametes, in plants, they can be stably inherited for many generations," says Frank Johannes, Professor of Population Epigenetics and Epigenomics at the Technical University of Munich (TUM), whose research team has been trying to understand how epimutations arise in plant genomes, how stable they are across generations, and whether they can affect important plant characteristics.
Trees are natural epimutation accumulation systems
"Given their extraordinary longevity, trees act as natural epimutation accumulation systems, and therefore offer unique insights into epigenetic processes over long time-scales," says Professor Johannes. Together with co-senior author Professor Robert J. Schmitz (University of Georgia, USA), who is also a Hans Fisher Fellow at the TUM-IAS, he recently published two companion papers on this topic.
In their studies, the team focused on a 330 year-old poplar tree. By comparing DNA methylation (an important epigenetic mark) of leaves from different branches of the tree, they were able to show that epimutations accumulate continuously as a function of the tree's age. The researchers found that the further apart two leaves are from each other, in terms of developmental time, the more dissimilar their DNA methylation patterns are. From this, the researchers were able to conclude that the rate of somatic epimutations is about 10,000 times higher than the genetic mutation rate in this same tree.
An epigenetic ageing clock in trees?
This discovery led to the intriguing insight that epimutations can serve as a kind of molecular clock to determine the age of a tree. "Only some branches had been dated by counting tree rings, but unfortunately not the main stem. We really needed this information for our analysis, so we decided to treat the total age of the tree as an unknown parameter and let the DNA methylation data of the leaves tell us how old the tree is. This gave an estimate of about 330 years," says Professor Johannes.
The estimate later turned out to be consistent with diameter-based dating of the main stem and with other information on the life history of this particular tree. "This was the first indication that there is something like an epigenetic clock in trees."
A window into the past
The team around Prof. Johannes is now pursuing the question whether environmental changes that trees experience over their long life-times leave epigenetic signatures that can be read and interpreted to learn something about their past.
"Our goal is to integrate historical environmental data with our epigenetic work. We think this may offer a window into the past which can help us to understand how trees have dealt with specific environmental challenges such as droughts and temperature fluctuations. This type of information may be useful when considering the future, particularly in light of global climate change."
CAPTION
Researchers want to correlate data of the environmental history of trees with their epigenetic work to offer a window into the past which can help to understand how trees have dealt with specific environmental challenges such as droughts and temperature fluctuations.
More Information
In an ongoing follow-up project, Frank Johannes is working together with Hans Pretzsch, Professor of Forest Growth and Yield Science (https://www.waldwachstum.wzw.tum.de/en/) at the TUM. His department is heading a European beech experiment in the Steigerwald in Central Germany, where individual trees have been closely observed since their first planting in 1870. Detailed growth and climate data are available for these tress. They have now been investigating if and how the developmental history of these trees can be reconstructed using epigenetic measurements.
CAPTION
Poplar trees tell scientists of their life
Geoscientists discover Ancestral Puebloans survived from ice melt in New Mexico lava tubes
A lava tube in the El Malpais National Monument yields centuries-old insights of survival in the face of harsh climate change
IMAGE: ICE DEPOSIT AT THE EL MALPAIS NATIONAL MONUMENT IN NEW MEXICO. view more
CREDIT: UNIVERSITY OF SOUTH FLORIDA
TAMPA, Fla. (Nov. 18, 2020)- For more than 10,000 years, the people who lived on the arid landscape of modern-day western New Mexico were renowned for their complex societies, unique architecture and early economic and political systems. But surviving in what Spanish explorers would later name El Malpais, or the "bad lands," required ingenuity now being explained for the first time by an international geosciences team led by the University of South Florida.
Exploring an ice-laden lava tube of the El Malpais National Monument and using precisely radiocarbon- dated charcoal found preserved deep in an ice deposit in a lava tube, USF geosciences Professor Bogdan Onac and his team discovered that Ancestral Puebloans survived devastating droughts by traveling deep into the caves to melt ancient ice as a water resource.
Dating back as far as AD 150 to 950, the water gatherers left behind charred material in the cave indicating they started small fires to melt the ice to collect as drinking water or perhaps for religious rituals. Working in collaboration with colleagues from the National Park Service, the University of Minnesota and a research institute from Romania, the team published its discovery in "Scientific Reports."
The droughts are believed to have influenced settlement and subsistence strategies, agricultural intensification, demographic trends and migration of the complex Ancestral Puebloan societies that once inhabited the American Southwest. Researchers claim the discovery from ice deposits presents "unambiguous evidence" of five drought events that impacted Ancestral Puebloan society during those centuries.
"This discovery sheds light on one of the many human-environment interactions in the Southwest at a time when climate change forced people to find water resources in unexpected places," Onac said, noting that the geological conditions that supported the discovery are now threatened by modern climate change.
"The melting cave ice under current climate conditions is both uncovering and threatening a fragile source of paleoenvironmental and archaeological evidence," he added.
Onac specializes in exploring the depths of caves around the world where ice and other geological formations and features provide a window to past sea level and climate conditions and help add important context to today's climate challenges.
Their study focused on a single lava tube amid a 40-mile swatch of treacherous ancient lava flows that host numerous lava tubes, many with significant ice deposits. While archaeologists have suspected that some of the surface trails crisscrossing the lava flows were left by ancient inhabitants searching for water, the research team said their work is the earliest, directly dated proof of water harvesting within the lava tubes of the Southwest.
The study characterizes five drought periods over an 800-year period during which Ancestral Puebloans accessed the cave, whose entrance sits more than 2,200 meters above sea level and has been surveyed at a length of 171 meters long and about 14 meters in depth. The cave contains an ice block that appears to be a remnant of a much larger ice deposit that once filled most of the cave's deepest section. For safety and conservation reasons, the National Park Service is identifying the site only as Cave 29.
In years with normal temperatures, the melting of seasonal ice near cave entrances would leave temporary shallow pools of water that would have been accessible to the Ancestral Puebloans. But when the ice was absent or retreated in warmer and dryer periods, the researchers documented evidence showing that the Ancestral Puebloans repeatedly worked their way to the back of the cave to light small fires to melt the ice block and capture the water.
They left behind charcoal and ash deposits, as well as a Cibola Gray Ware pottery shard that researchers found as they harvested a core of ancient ice from the block. The team believes the Ancestral Puebloans were able to manage smoke within the cave with its natural air circulation system by keeping the fires small.
The discovery was an unexpected one, Onac said. The team's original goal in its journey into the lava tube was to gather samples to reconstruct the paleoclimate using ice deposits, which are slowly but steadily melting.
"I have entered many lava tubes, but this one was special because of the amount of charcoal present on the floor in the deeper part of the cave," he said. "I thought it was an interesting topic, but only once we found charcoal and soot in the ice core that the idea to connect the use of ice as a water resource came to my mind."
Unfortunately, researchers are now racing against the clock as modern climate conditions are causing the cave ice to melt, resulting in the loss of ancient climate data. Onac said he recently received support from the National Science Foundation to continue the research in the lava tubes before the geological evidence disappears.
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Joining in the exploration and research were Dylan S. Parmenter, whose master's degree at USF was on the topic and is now a doctoral student at the University of Minnesota, Steven M. Baumann and Eric Weaver of the National Park Service, and Tiberiu B. Sava of the Horia Hulubei National Institute for Physics and Nuclear Engineering in Romania. The research was funded by the National Park Service and the National Science Foundation.
