A researcher from the Xishuangbanna Tropical Botanical Garden (XTBG) said in a floristic study that the majority of fern species in the forest habitat of Xishuangbanna of Yunnan province are locally rare. Two-thirds of terrestrial fern species and nearly all epiphytes are rare.
Using a transect-based method, the researcher conducted a floristic study at 75 sites to investigate the richness and cover of terrestrial and epiphytic fern species in Xishuangbanna.
It was found a total of 130 fern species, including 99 terrestrial (i.e. self and non-self-supporting, as climbers and as individuals with rhizomes in the soil) species and 31 epiphytes (i.e. growing on a trunk or tree crown). 66% of the terrestrial and 99% of the epiphytes are rare in Xishuangbanna.
He evaluated whether the richness of the common and rare species was different between the drier and humid site, and tried to find whether elevation played a major role for the cover values of rare and common fern species.
He found that the rare species are more frequent at higher elevations with the driest sites being slightly richer in terms of the epiphytes and the total number of species. However, the richness and cover of the terrestrial species was higher at lowland sites.
According to the investigation, most of the fern species have a narrow and or wide distribution but low cover values, showing that the fern species in Xishuangbanna tend to have a population size characterized by low cover and few individuals.
“Since there are so many rare fern species with low occurrence, it is urgent to conserve biodiversity in the fragmented tropical landscape of southern Yunnan,” said Daniele Cicuzza, author of the study.
Beta-cyclocitral produced by plants after herbivore attack increases defense responses while inhibiting the production of metabolites for growth.
In a new study in PNAS, an international team of researchers including scientists from the Max Planck Institute for Chemical Ecology has shown that Arabidopsis thaliana plants produce beta-cyclocitral when attacked by herbivores and that this volatile signal inhibits the methylerythritol 4-phosphate (MEP) pathway. The MEP pathway is instrumental in plant growth processes, such as the production of pigments for photosynthesis. In addition to down-regulating the MEP pathway, beta-cyclocitral also increases plant defenses against herbivores. Since the MEP pathway is only found in plants and microorganisms, but not animals, knowledge of a signal molecule like beta-cyclocitral opens up new possibilities for the development of herbicides or antimicrobial agents that block this pathway (Proceedings of the National Academy of Sciences of the United States of America, March 2021, doi:10.1073/pnas.2008747118).
Trade-offs between defense and growth processes in plants
Researchers have long known that plants have limited resources that they can invest in defense against enemies or in growth and reproduction, depending on their environmental conditions. Many studies have already shown that plants increase their defenses when attacked by insects producing, for example, toxins or inhibitors of digestive enzymes that harm their attackers. However, much less is known about how herbivore attack affects growth processes in the plant. “We wanted to investigate how herbivory might affect photosynthesis and the methylerythritol 4-phosphate (MEP) pathway, a pathway making metabolites for growth that is directly supplied from photosynthesis,” says first author Sirsha Mitra, who had started working on this project at the Max Planck Institute and is now an assistant professor at Savitribai Phule Pune University in Pune, India.
The MEP pathway has been a research topic at the Max Planck Institute for Chemical Ecology in Jena for several years “The MEP pathway makes the building blocks for plant isoprenoids or terpenoids, a very large family of plant metabolites involved in growth, defense and signaling,” says Jonathan Gershenzon, the head of the Department of Biochemistry and one of the authors.
Beta-cyclocitral activates defense and inhibits growth
The international research team, which also included partners from the Universitat Ramon Llull in Barcelona, Spain, the Technical University in Lyngby, Denmark, and the University of Toronto, Canada, demonstrated that plants of the thale cress Arabidopsis thaliana which were fed to caterpillars of the African cotton leafworm, a generalist feeder that attacks many different plant species, increased defenses while simultaneously reducing growth processes. Using a variety of techniques from molecular biology and analytical chemistry, as well as caterpillar bioassays, the scientists were able to show that a specific volatile compound, beta-cyclocitral, formed by cleavage of beta-carotene due to a reactive form of oxygen, was responsible for this shift of resources. While beta-cyclocitral acts as a chemical signal to increase defenses, it simultaneously decreases the formation of compounds in the MEP pathway by directly inhibiting the rate-controlling enzyme of this pathway. “Of particular importance to our study was the exposure of plants to isotopically labeled carbon dioxide (13CO2) instead of the dominant atmospheric carbon dioxide (12CO2). Carbon dioxide is easily introduced into the MEP pathway via photosynthesis. This allowed us to track how the metabolic flux in the MEP pathway changed when plants switched to a defensive mode after herbivore attack and beta-cyclocitral slowed down the MEP pathway,” says Louwrance Wright, one of the lead authors who is now working in South Africa. Caterpillars feeding on plants treated with beta-cyclocitral exhibited decreased growth in comparison to caterpillars feeding on untreated plants. This is further evidence of the importance of this volatile signal for plant defense.
Potential benefits in agriculture and medicine
When plants are attacked, they may have to stop growth processes in order to release sufficient resources for their defense. Beta-cyclocitral signaling is a mechanism that precisely controls this shift in resources. Beta-cyclocitral, or a more stable derivative, could therefore be applied to crops to stimulate defenses during a pest outbreak. “Since the MEP pathway is found in all plants and many microorganisms, but not in animals, it is of particular interest for the development of herbicides, as well as drugs with antimicrobial activity,” says Jonathan Gershenzon, explaining the potential applications of this research. Further studies in India will now investigate whether beta-cyclocitral can increase insect resistance in crops, such as tomatoes, and whether it interacts with other already known defense signals.
Featured image: Feeding by herbivores not only causes plants to produce defense compounds, but also leads to a slowdown in growth processes. Cleavage of beta-carotene (a photosynthetic pigment) via reactive forms of oxygen (ROS = reactive oxygen species), forms beta-cyclocitral (βCC), which directly inhibits the rate-controlling enzyme of the MEP pathway located in the chloroplast. Graphic: Kimberly Falk, Moves Like Nature
Original Publication: Mitra, S., Estrada-Tejedor, R., Volke, D. C., Phillips, M. A., Gershenzon, J., Wright, L. (2021). Negative regulation of plastidial isoprenoid pathway by herbivore-induced β-cyclocitral in Arabidopsis thaliana. Proceedings of the National Academy of Sciences of the United States of America, 118(10): e2008747118. doi:10.1073/pnas.2008747118 https://doi.org/10.1073/pnas.2008747118
Restoring habitat requires much more than just the right plants
If you build it, they might not come. That’s the key finding of a new study on habitat restoration practices that challenges a commonly accepted principle in ecology.
The study tested the “Field of Dreams” hypothesis, which predicts that restoring plant biodiversity will lead to recovery of animal biodiversity. The prediction, which often guides restoration practices, is infrequently tested because restoration studies typically measure plant or animal biodiversity, but rarely both, said lead author Pete Guiden, a post-doctoral researcher at Northern Illinois University.
Guiden and NIU colleagues studied 17 research plots of restored tallgrass prairie, measuring biodiversity in four animal communities—snakes, small mammals and ground and dung beetles. “We wanted to know if the most diverse animal communities were found in the most diverse plant communities, or if something else is responsible for patterns of animal biodiversity,” he said.
While the scientists did find some positive connections between plant and animal biodiversity, the gains weren’t nearly as strong as benefits derived from implementation of restoration management strategies.
“We found that the effects of management strategies like controlled burns and bison reintroduction on animal communities were six times stronger on average than the effects of plant biodiversity,” Guiden said.
“The most important effects of restoration on animal biodiversity had little to do with plant community biodiversity,” he added. “So management practices focused on restoring plants might be insufficient to also restore animals.”
Co-authors include NIU professors Holly Jones (biology, environmental studies) and Richard King (biology); NIU post-doctoral fellow John Vanek; NIU graduate student Erin Rowland; former NIU students Ryan Blackburn, Anna Farrell, Jessica Fliginger, Sheryl C. Hosler, Melissa Nelson and Kirstie Savage; and former NIU professor Nicholas Barber of San Diego State University.
“This is an important study,” said Jones, whose Evidence-based Restoration Laboratory at NIU carried out the research. “With Earth’s biodiversity rapidly disappearing, ecological restoration has emerged as an important strategy to slow or reverse biodiversity losses. Critical tests of the Field of Dreams and other hypotheses are needed to improve restoration science and ensure we get the most bang for our buck.”
The study results were a surprise to the authors, who had predicted that plant biodiversity would have stronger effects on animal biodiversity than management strategies.
“We expected plant biodiversity to be important because having more plant species allows animals to split up food resources or habitat,” Guiden said. “However, the strong effects of land management on animal biodiversity highlight the important role of people in shaping the quantity or quality of habitat, especially through disturbance regimes used in restoration.”
The scientists’ work was conducted at Nachusa Grasslands, a 3,800-acre nature preserve in Franklin Grove, Illinois, managed by The Nature Conservancy. Since 1986, Nachusa crew members and volunteers have been reconnecting remnant prairie, woodlands and wetlands through habitat restoration to create one of the largest and most biologically diverse grasslands in Illinois. Tallgrass prairie is one of the most globally imperiled ecosystems.
“While Illinois is known as the Prairie State, 99.9 percent of its prairie has been lost to agriculture and development,” Jones said. “Nachusa Grasslands is an incredible success story. What The Nature Conservancy has done is show us we can restore ecosystems. What was once rows of corn is now a really high-functioning prairie that also serves as a living laboratory for restoration scientists.”
The 17 research sites studied measured 60-by-60 meters and had restoration ages spanning three to 32 years. Each site experienced a unique controlled-burn history, and bison had been reintroduced to eight of the sites between 2014 and 2015. For Nachusa Grasslands, fire and bison-grazing are key management practices that are components of healthy prairies and together can increase plant and animal biodiversity.
By simultaneously measuring plant and animal responses to restoration disturbances, the scientists were able to tease out and compare management-driven and plant-driven effects.
Guiden said each animal community studied differed considerably in its specific responses to restoration. In fact, the study found that restoration can simultaneously have positive and negative effects on biodiversity through different pathways, which may help reconcile why there can be variation in restoration outcomes.
For example, in older restorations, high diversity among plants resulted in a decrease in a specific diversity measure for dung beetles, likely because key resources became more difficult to find. On the other hand, older restorations also had soil conditions that provided high quality habitat for a wide range of other species.
Guiden also noted that the animals studied in this research project are decomposers (dung beetles), omnivores (small mammals) or carnivores (snakes, ground beetles). “Animal communities composed of herbivores, particularly species highly specialized on specific prairie plants, may show stronger relationships to plant diversity,” he said.
Ecosystems are difficult to restore because they represent such highly intricate webs of species’ interactions with each other and their environments, Jones said.
“Our study shows that it’s critical to define restoration goals before projects get off the ground and to measure progress,” she said. “This will help ensure the restoration is eliciting the desired responses.
“Perhaps more importantly, our study shows these active restoration techniques of introducing megaherbivores like bison, which were near extinction last century, and fire regimes that Indigenous people used to set to prairies, are absolutely critical components to recreating those complex webs of species and interactions. Seeding alone gets us started, but extra management super charges the animal communities that are critical to maintaining healthy prairies.”
Featured image: The new study found that, when restoring habitat, the effects of management strategies on animal communities were six times stronger on average than the effects of plant biodiversity. One such management strategy in prairie restoration is the reintroduction of bison, seen here at Nachusa Grasslands. Credit: Holly Jones
Reference: Peter W. Guiden, Nicholas A. Barber, Ryan Blackburn, Anna Farrell, Jessica Fliginger, Sheryl C. Hosler, Richard B. King, Melissa Nelson, Erin G. Rowland, Kirstie Savage, John P. Vanek, Holly P. Jones, “Effects of management outweigh effects of plant diversity on restored animal communities in tallgrass prairies”, Proceedings of the National Academy of Sciences Feb 2021, 118 (5) e2015421118; DOI: 10.1073/pnas.2015421118
Tree rings, with their special characteristics of precise dating, annual resolution, long time series and climate sensitivity, have been widely considered a useful proxy for past climate variations.
Researchers at the Institute of Botany of the Chinese Academy of Sciences have given an overview on using tree rings to identify climate regime shifts in a perspective paper entitled “Tree rings circle an abrupt shift in climate,” which was published in Science on Nov. 26.
In the paper, Prof. ZHANG Qi-Bin and Dr. FANG Ouya provided background in the field and discussed its advances. They also referenced a paper reporting a recent climate regime shift to a hotter and drier climate over inner East Asia, which was written by lead author ZHANG Peng from South Korea and published in the same issue of Science.
“Careful attention is required when using tree rings to reconstruct a specific climate variable over a large geographical region,” said Prof. ZHANG Qi-Bin. “Signals from the macroclimate must be extracted efficiently while removing the nonclimate noise embedded in the tree rings.”
Changes in climate have dramatic effects on natural ecosystems and human society. Less well understood is whether these changes are irreversible beyond a certain tipping point, that is, whether they represent a climate regime shift.
Scientists worldwide are alarmed about the potential risks of abrupt climate changes and their impacts on ecosystems and society, yet it is still difficult to identify the exact occurrence of climate regime shifts.
To judge whether climate systems undergo regime shifts from one steady state to another, scientists must understand the natural range of climate variability over a time scale that is much longer than the new regime.
ZHANG Peng et al. compiled tree-ring width data from 76 sites throughout inner East Asia and successfully screened 20 sites with strong signals of summer heatwave frequency and soil moisture content.
They found that the magnitude of the warm and dry anomalies compounding in the past two decades is unprecedented over the past 260 years. They further illustrated that the heatwaves and droughts became tightly coupled, which is likely caused by a pronounced enhancement of land-atmosphere coupling along with anthropogenic climate change.
However, it is still challenging for scientists to disentangle the interaction of climate variables and clarify whether these interactions generate negative or positive feedbacks, according to Prof. ZHANG Qi-Bin and Dr. FANG.
Furthermore, spatial differences related to climate regime shifts are worthy of study.
Using tree-ring data as a proxy for past climate variability and forest dynamics, Prof. ZHANG Qi-Bin’s lab has long been engaged in investigating the responses of tree growth to multiple dimensions of climate change and ecological disturbances, and in exploring spatial and temporal patterns of forest health.
2020 is the worst fire year on record in the United States, with nearly 13 million acres burned, 14,000 structures destroyed and an estimated $3 billion spent on fire suppression — and counting. At the same time, certain land managers have invested huge amounts of time and resources toward restoring fire through “controlled burn” approaches.
In the face of heartbreaking losses, effort and expense, scientists are still grappling with some of the most basic questions about how fire influences interactions between plants and animals in the natural world.
A new study grounded in the northern Rockies explores the role of fire in the finely tuned dance between plants and their pollinators. Published Nov. 25 in the Journal of Ecology, the findings from researchers at Washington University in St. Louis, Marquette University, Montana State University and The Wilderness Society are particularly significant in light of recent reports about the rapid and widespread decline of insects globally.
“A large number of studies have looked at how fire affects plants, or how fire affects animals. But what is largely understudied is the question of how fire affects both, and about how linkages within those ecological networks might respond to fire disturbance,” said Jonathan Myers, associate professor of biology in Arts & Sciences at Washington University, a co-author of the study.
The researchers discovered that wildfire disturbance and plant-pollinator interactions are both important in determining where plants take root and where pollinators are found. But in burned landscapes, plant-pollinator interactions are generally as important or more important than any other factor in determining the composition of species present.
The importance of flowering-plant species in determining the composition of pollinator species doubled to quadrupled following wildfire. In addition, the importance of pollinators in determining plant composition nearly doubled following wildfire.
“Clearly, pollinators perform a valuable ecosystem service for humans by pollinating all our crops. In intact natural ecosystems, they perform an equally valuable service,” said Joseph LaManna, assistant professor of biological sciences at Marquette University, first author of the study. “What we are seeing is that plant and pollinator linkages become even more important in disturbed or burned landscapes. These connections are important for restoring ecosystems in which natural wildfire regimes have been altered or suppressed by human activities.
“And as climate change increases the frequency and intensity of wildfires, the potential for biodiversity loss — for losses of individual plant or pollinator species — is going to be even more profound than we anticipated,” he said.
Feeling the burn
Wildfire in the northern Rockies can be ignited by lightning — but more and more, it is started by people.
Historically, wildfires tended to burn hot in some spots and cold in others, resulting in a patchwork or mosaic of differing levels of fire disturbance. But with rising global temperatures, the plant debris and other materials that fuel fires are drying out. That trend combined with decades of active fire suppression has resulted in a shift from a majority mixed-severity wildfire regime to today’s high-severity blazes.
For this study, co-author Laura Burkle at Montana State University led the field inventories of plants and pollinators at 152 plots in Montana representing a wildfire gradient including plots with no recent wildfire (unburned), mixed-severity wildfire and high-severity wildfire. LaManna and Myers worked with Burkle and Travis Belote of The Wilderness Society to analyze the data.
At the sites they compared, the scientists found that the number of individual bees, flies and butterflies — and the flowering plants they frequent — were higher in parts of the landscape that had burned, as opposed to those that hadn’t burned.
However, increases were greater in areas that had experienced mixed-severity wildfire, which leaves some vegetation intact in a mosaic of habitat types, as opposed to high-severity wildfire, which largely removes all vegetation and can damage the soil and seed bank.
For example, flowering-plant abundances increased more than 10-fold in mixed-severity wildfire and more than nine-fold in high-severity wildfire compared with unburned areas. Overall the researchers identified 329 pollinator species and 193 flowering-plant species.
“Oftentimes, the public perception about fire in general is that it is bad. But it was impressive how much higher the abundances of both plants and pollinators were — as well as the number of species — in the burned landscapes compared with the unburned landscapes,” Myers said.
Leave it to the bees
Although this study shows that fire increased abundances and species diversity of pollinators and flowering plants overall, the intensity of the fire matters. Hotter, high-severity burns can eliminate landscape features that pollinators require, like stumps or woody debris for nesting. Mixed-severity wildfire is most beneficial.
Around the world, pollinator populations are in decline. The northern Rockies are no exception to this troubling trend.
“Thanks to this project, we now have very in-depth knowledge of local pollinator communities, especially the bee communities,” Burkle said. “One of the benefits of these data is to be able to provide expert knowledge about declining pollinator species and species of concern, like the Western Bumble Bee (Bombus occidentalis), which is currently being considered for federal listing under the Endangered Species Act.
“When we think about patterns of biodiversity across space, we typically consider different groups of species separately,” she said. “In our case, we might consider patterns of plant diversity separately from patterns of pollinator diversity. But our study provides solid evidence that — above and beyond the influence of disturbances like wildfires — the relationships that plants have with pollinators are strong contributors to these patterns of biodiversity.
“This means that biotic interactions among species are important and will need to be considered more explicitly in conservation actions, like plans for species range shifts with climate change.”
Global climate change is likely to increase the frequency and intensity of wildfires in many other regions — as it has in the mountain West, the researchers said.
The findings from this study suggest that this could possibly result in additional losses of vulnerable species.
“We may see wildfire accelerating co-extinction events where you lose a pollinator and then you lose all of the plants that the pollinator depended on — and then you lose more pollinators that were associated with those plants, and so on,” LaManna said. “You have a potential for a chain of losses.”
Overall, this research advances understanding of how and why wildfire affects conservation, land management and restoration of forest ecosystems. It also shows that ecological models that predict how species will respond under various climate change scenarios also should consider biological interactions within food webs, Myers said.
“By sharing our findings with federal land managers across the region, we hope to contribute to management plans, with the dual aim of maintaining biodiversity of plants and pollinators while restoring environmental complexity representative of historical fire regimes,” Myers said.
Study shows that a tree frog endemic to a mountainous region of the Brazilian savanna is unable to disperse and find genetically closer mates when the terrain is rugged, potentially endangering survival of the species.
The savanna tree frog Bokermannohyla ibitiguara is about 4 cm long and is found only in gallery forest along streams in the Serra da Canastra mountain range in the state of Minas Gerais, Southeast Brazil. In this watery forest environment, it can grow, feed, mate, and lay eggs without needing to range very far throughout its life cycle, according to a study published in Diversity and Distributions.
According to the Brazilian and US researchers who conducted the study, topography rather than vegetation is the main factor leading to more or less dispersal of the species in the territory, and this information is even recorded in its DNA.
They analyzed genetic variation among groups of B. ibitiguara living inside and outside the Serra da Canastra National Park, a protected area in the region, discovering that the flatter the terrain, the more genetically diverse is the population.
In areas of highly variable elevation, individuals are genetically similar. In evolutionary terms, this can be harmful to the species, which becomes more susceptible to disease and climate change, for example.
“Genetic analysis and conservation studies typically take land cover into account, among other factors, but the Cerrado [Brazilian savanna] is topographically diverse, including montane regions with high plateaus [chapadões] separated by low areas. We set out to verify whether this variable terrain played a part in the genetic diversity of the species, and found that it did. The vegetation alone didn’t explain the genetic differences we identified between sites, or even within the same site. The topography did,” said Renato Christensen Nali, first author of the article and a professor at the Federal University of Juiz de Fora’s Institute of Biological Sciences (ICB-UFJF) in Minas Gerais, Brazil.
The study was one of the results of Nali’s doctoral research, conducted at São Paulo State University’s Bioscience Institute (IB-UNESP) in Rio Claro, Brazil, with a scholarship from FAPESP (São Paulo Research Foundation).
The research was part of the project “Reproductive ecology of anuran amphibians: an evolutionary perspective”, for which the principal investigator is Cynthia Peralta de Almeida Prado, a co-author of the article. She is a professor at UNESP’s School of Agrarian and Veterinary Sciences in Jaboticabal and teaches graduate students in zoology at IB-UNESP in Rio Claro.
The flatter the better
“The findings are very interesting because they bring to light a novel factor for conservation of the Cerrado, among other reasons. Ecological corridors and native forests are rightly considered important for conservation units, but more attention needs to be paid to the type of terrain. The topography should permit dispersal of the animals,” said Nali, who heads ICB-UFJF’s Amphibian Evolutionary Ecology Laboratory (Lecean).
To arrive at the results, the researchers analyzed 12 populations of B. ibitiguara, six inside Serra da Canastra National Park and six outside. Genetic diversity was much higher among the anurans living in the protected area than among those living outside the park. When the researchers correlated information on the degree of protection of the areas with the state of the vegetation, they found that these factors were less decisive for genetic diversity than the topography.
“The terrain is much more rugged outside the park, whereas inside it there’s a large, very even plateau where the anurans can disperse more, find mates in more distant areas, and increase their genetic diversity,” Nali said. “Outside the park, the rugged terrain and variable elevation appear to confine them to small areas.”
The influence of these factors was evidenced by genetic tests. The researchers used a technique known as macrosatellite marker analysis to examine specific regions of the genome and found higher allele diversity in the populations living in the park. Allele diversity is one of the determinants of genetic integrity and adaptive potential.
In addition, the populations living outside the park displayed a greater loss of heterozygosity. If this loss, which is associated with declining genetic variability, recurs across several generations, it can eventually threaten the population’s survival.
The study underscores the importance of topography as a factor to consider in conservation studies, as well as showing how the mere presence of a species in an area cannot ensure that it is not endangered.
“Molecular analysis enables us to find out if a population’s genetic status is favorable,” Nali said. “An area may have a large number of individuals, but DNA analysis may show that its genetic constitution is unfavorable, with few alleles and low heterozygosity. In practice, therefore, the population’s effective size is small.”
Although the study focused on only one species, he added, the findings can apply to others as well since the physical characteristics associated with dispersal are similar for other frogs and toads. More species need to be investigated to confirm the applicability of the findings.
The group noted that land cover nevertheless remains an important factor for conservation in the Cerrado, more than 50% of which has been converted into pasture or cropland, while less than 5% is protected by conservation units.
References: Nali, RC, Becker, CG, Zamudio, KR, Prado, CPA. Topography, more than land cover, explains genetic diversity in a Neotropical savanna tree frog. Divers Distrib. 2020; 26: 1798– 1812. https://doi.org/10.1111/ddi.13154
It’s clear to see that species like tree frogs have gigantic eyes, but the visual systems of most frogs have gone largely unstudied by scientists.
An international, interdisciplinary team of researchers is starting to change that. In the first study to come out of the collaboration, the team examined museum specimens representing all 55 frog families to test hypotheses about the evolution of frog eye size and its relationship to different aspects of their lifestyles. The results show that, overall, frogs are investing a lot of energy in maintaining their eyes and that vision is likely important to their survival and reproductive success.
Rayna Bell, assistant curator of herpetology at the California Academy of Sciences and one of the new paper’s authors, says that although frogs were an early model for studying vision at the turn of the 20th century, the research was limited to a small number of easily accessible species.
“It was not reflective of the enormous diversity of frogs that we know exist today,” she says. “Our understanding of vision in frogs has lagged behind such research in other vertebrates, such as fishes, birds, and mammals.”
There are more than 7,000 frog species living in a variety of different habitats and ecosystems: Some spend their entire lives underwater, others live in the treetops, and others burrow underground.
The first goal of Bell and her colleagues was to broaden out from those initial frog species whose vision had been characterized historically and document the diversity in eye size among frogs. To do this, her team depended primarily on specimens preserved in natural history collections around the world. They measured eye size in 220 frog species representing all 55 families.
The study revealed that frogs have relatively large eyes for their body size, with certain species of tree frog coming out on top. Bell says that relative eye size is an indication of how much of an organism’s energy budget is invested in eye tissue.
“Eyes are metabolically expensive to maintain, so if you have large eyes, that suggests you are relying pretty heavily on vision and investing energy in maintaining that eye tissue,” she says.
The team also tested whether eye sizes were correlated with life history traits like where the frogs lived or whether they are active at day or night. As is seen in other animals, there was a strong association between habitat type and eye size, with species that live underground or in murky water having reduced eyes. It’s likely that in these light-deficient environments, animals are not relying as much on vision and it’s not worth it to invest in growing large eyes.
Bell says this study is an important first step in understanding the diversity of eye size in frogs. Next, she and her colleagues are looking at the genetic underpinnings of this variation and characterizing photoreceptor sensitivity in different frogs. She’s also interested in how frogs’ visual systems change as they develop from aquatic tadpoles into adults who might live in a very different habitat.
“It’s interesting from an evolutionary perspective but also from a behavioral perspective, in terms of understanding how frogs are sensing and interacting with their environment,” says Bell.
“We know that they have big eyes. We don’t know specifically why but we’re working on it.”
References: Thomas KN, Gower DJ, Bell RC, Fujita MK, Schott RK, and Streicher JW. (2020). Eye size and investment in frogs and toads correlate with adult habitat, activity pattern and breeding ecology. Proceedings of the Royal Society B 287: 20201393. Doi: 10.1098/rspb.2020.1393.
This article is republished here from psychology today under common creative licenses
According to a team of ecologists from RUDN University, polycyclic aromatic hydrocarbons (PAHs) can be used as pollution indicators and help monitor the movement of pollutants in environmental components such as soils, plants, and water. To find this out, the team conducted a large-scale study of a variety of soil, water, and plant samples collected from a vast area from China to the Antarctic. The results of the study were published in the Applied Geochemistry journal.
Geochemical barriers mark the borders between natural environments at which the nature of element transfer changes dramatically. For example, the concentration of oxygen rapidly increases at groundwater outlets, because different chemical elements oxidize and accumulate on the barrier. A team of ecologists from RUDN University was the first in the world to suggest a model that describes the energy of mass transfer, i.e. the movement of matter in an ecosystem. In this model, polycyclic aromatic hydrocarbons (PAHs) are used as the markers of moving substances. PAHs are mainly toxic organic substances that accumulate in the soil. The team used their composition to monitor pollutions and track down their sources. To do so, the ecologists calculated the physical and chemical properties of PAHs and classified them.
“We developed a model that shows the accumulation, transformation, and migration of PAHs. It is based on quantitative measurements that produce more consistent results than descriptive visualizations. This helped us understand how physical and chemical properties of PAHs determine their accumulation in the environment,” said Prof. Aleksander Khaustov, a PhD in Geology and Mineralogy, from the Department of Applied Ecology at RUDN University.
PAHs can form due to natural causes (e.g. wildfires) or as a result of human activity, for example as the waste products of the chemical and oil industry. The team studied 142 water, plant, soil, and silt samples from different geographical regions. Namely, some samples were taken in the hydrologic systems of the Kerch Peninsula, some came from leather industry areas in China, from the vicinity of Irkutsk aluminum smelter, and different regions of the Arctic and Antarctic. Several snow samples were taken on RUDN University campus in Moscow. All collected data were unified, and then the amount of PAHs in each sample was calculated. After that, the results were analyzed in line with the thermodynamic theory to calculate entropy, enthalpy, and Gibbs energy variations. The first value describes the deviation of an actual process from the ideal one; the second one shows the amounts of released or consumed energy, and the third points out the possibility of mass transfer.
“Though our samples were not genetically uniform, they allowed us to apply thermodynamic analysis to matter and energy transfer in natural dissipative systems,” added Prof. Aleksander Khaustov.
The team identified several factors that have the biggest impact on PAHs accumulation. For example, in the ecosystems surrounding leather facilities in China, the key factor turned to be entropy variations, while on RUDN University campus it was the changes in Gibbs energy. The team described three types of processes that are characterized by the reduction, stability, or increase of all three thermodynamic parameters, respectively. Based on this classification and the composition of PAHs one can monitor pollution and track down its source.
According to recent study done by Blai Vidiella and colleagues, by tweaking the genes of microbes in the soil, it may be possible to make arid ecosystems more resilient to climate change and overgrazing. The research is in early stages, and currently consists of theoretical work using computer models. But the models suggest that even relatively small changes to key organisms could have profound effects.
According to Ricard Sole, a biophysicist at Pompeu Fabra University in Spain, Water-scarce regions, known as “drylands,” cover roughly 40% of Earth’s land area and are home to about 40% of the human population. Many drylands host productive ecosystems that are adapted to low levels of moisture. But when such ecosystems are subject to overgrazing or a warming climate, they can collapse and turn into much less hospitable deserts. These collapses often happen suddenly, after ecosystems pass a “tipping point.”
Solé and his colleagues are working to see whether genetic changes to microorganisms could shift these tipping points. For example, it may be possible to take photosynthetic bacteria that already live in dryland soils and splice in genes that allow them to store more water or capture more phosphorus. These engineered bacteria could then enrich the soil, allowing plants to grow and create shade, which would then support the growth of more bacteria.
Sole describes such mutually beneficial relationships between species as “cooperative loops.” In one set of models, he and his colleagues simulated the creation of new cooperative loops and observed how they affected the rest of the virtual ecosystem. In another set of models, they simulated microbes with increased ability to disperse and spread to new areas.
Both types of modifications allowed simulated ecosystems to function under drier conditions. In theory, engineered microbes might allow dryland ecosystems to survive for several more decades, giving humanity more time to address underlying problems such as climate change. The researchers plan to begin laboratory experiments with real organisms next year.
People often fear that engineered organisms could lead to “Jurassic Park”-type scenarios. Indeed, extensive testing would be needed to ensure the engineered microbes wouldn’t cause any unintended harm. But in Sole’s view, the urgent state of the environmental crisis may justify extreme measures.