Category Archives: Ecology

Stanford Ecologists Develop A Theory About How Plants ‘Pay’ Their Microbes (Ecology)

Combining economics, psychology and studies of fertilizer application, researchers find that plants nearly follow an “equal pay for equal work” rule when giving resources to partner microbes – except when those microbes underperform.

“Equal pay for equal work,” a motto touted by many people, turns out to be relevant to the plant world as well. According to new research by Stanford University ecologists, plants allocate resources to their microbial partners in proportion to how much they benefit from that partnership.

“The vast majority of plants rely on microbes to provide them with the nutrients they need to grow and reproduce,” explained Brian Steidinger, a former postdoctoral researcher in the lab of Stanford ecologist, Kabir Peay. “The problem is that these microbes differ in how well they do the job. We wanted to see how the plants reward their microbial employees.”

In a new study, published July 6 in the journal American Naturalist, the researchers investigated this question by analyzing data from several studies that detail how different plants “pay” their symbionts with carbon relative to the “work” those symbionts perform for the plants – in the form of supplying nutrients, like phosphorus and nitrogen. What they found was that plants don’t quite achieve “equal pay” because they tend not to penalize low-performing microbes as much as would be expected in a truly equal system. The researchers were able to come up with a simple mathematical equation to represent most of the plant-microbe exchanges they observed.

“It’s a square root relationship,” said Peay, who is an associate professor of biology in the School of Humanities and Sciences. “Meaning, if microbe B does one-quarter as much work as microbe A, it still gets 50 percent as many resources – the square root of one-quarter.”

When the researchers tested their equation against 13 measurements of plant resource exchange with microbe partners, they were able to explain around 66 percent of the variability in the ratio of plant payments to two different microbes.

“The biggest surprise was the simplicity of the model,” said Steidinger. “You don’t get a lot of short equations in ecology. Or anywhere else.”

The fruit of frustration

When asked about the motivation for developing this equation, Steidinger summed it up with one word: frustration.

“There is a lot of really interesting literature in a field called ‘biological market theory’ that deals with how plants should preferentially allocate resources. But for the folks who actually run experiments, it is difficult to translate these models into clean predictions,” said Steidinger. “We wanted to make that clean prediction.”

An informal survey of the Peay lab members encouraged the researchers to start with the assumption of equal pay because most people agreed it was reasonable to guess that plants treat all microbes the same. To reach their final equation, Steidinger and Peay then factored in the diminishing returns seen in the fertilizer models and assessed them through the lens of biological market theory literature – which uses human markets as a mathematical analogy for exchanges of services in the natural world.

“It turns out if the plant is flush with resources – in this case, the sugars it feeds to its microbes – and if the nutrients are valuable enough, the plant pays its microbes according to a square-root law,” said Peay.

The square-root model is a strong start to addressing Steidinger’s original frustration but it is not quite at the level of realism he wants to eventually achieve.

“For instance, our model allows a useless microbe to be fired without the plant losing resources,” said Steidinger. “But, just as in the human world, it takes an investment to hire a microbe and that initial investment is a gamble that microbial layabouts can consume at their leisure.”

Weber’s Law

In an attempt to explain why plants follow the square-root model, the researchers turned to a law in psychology. Weber’s Law addresses how humans perceive differences in stimuli, such as noise, light or the size of different objects. It explains that, the stronger the stimuli, the worse we are at identifying when it changes. This law has been shown to hold for many non-human animals as well – describing, for example, how birds and bats forage for food and how fish school. Now the researchers suggest it’s a good analogy for their plant payment scheme too.

“Our model says that plant should go easy on low-performing microbes, seemingly overpaying the 25-percent-as-good microbe with 50 percent as much resources,” said Peay. “Well, it’s long been known that humans and non-human animals sense differences in quantity in a way that might bias them towards similar leniency.”

In other words, the researchers suggest that, like a human trying to detect the volumes of specific noises in a loud room, a plant making optimal payment decisions may be relatively insensitive to differences in the quality of its microbial employees. And the researchers argue that this insensitivity may be for the best, as it encourages plants to maintain a certain level of microbial diversity, which can help give the plant options for dealing with environmental changes it encounters throughout its lifetime.

“I think what we’re seeing is plants behave like animals not because they have the same perceptional limitations – and certainly not because they think like animals – but because we face similar challenges in making the best choices when there are diminishing returns on investment,” says Steidinger.

This research was funded by the U.S. Department of Energy Office of Science, Office of Biological & Environmental Research, Early Career Research Program; the National Science Foundation Division of Environmental Biology; and an Alexander von Humboldt Postdoctoral Research Fellowship.

Featured image: Plants and microbes exchange resources in symbiotic relationships – but Stanford ecologists suggest that plants don’t quite compensate all their microbes equally. (Image credit: Getty Images)

Provided by Stanford University

World’s Lakes Losing Oxygen Rapidly As Planet Warms (Ecology)

Changes threaten biodiversity and drinking water quality

Oxygen levels in the world’s temperate freshwater lakes are declining rapidly — faster than in the oceans — a trend driven largely by climate change that threatens freshwater biodiversity and drinking water quality.

Research published today in Nature found that oxygen levels in surveyed lakes across the temperate zone have declined 5.5% at the surface and 18.6% in deep waters since 1980. Meanwhile, in a large subset of mostly nutrient-polluted lakes, surface oxygen levels increased as water temperatures crossed a threshold favoring cyanobacteria, which can create toxins when they flourish in the form of harmful algal blooms.

“All complex life depends on oxygen. It’s the support system for aquatic food webs. And when you start losing oxygen, you have the potential to lose species,” said Kevin Rose , author and professor at Rensselaer Polytechnic Institute. “Lakes are losing oxygen 2.75-9.3 times faster than the oceans, a decline that will have impacts throughout the ecosystem.”

Researchers analyzed a combined total of over 45,000 dissolved oxygen and temperature profiles collected since 1941 from nearly 400 lakes around the globe. Most long-term records were collected in the temperate zone, which spans 23 to 66 degrees north and south latitude. In addition to biodiversity, the concentration of dissolved oxygen in aquatic ecosystems influences greenhouse gas emissions, nutrient biogeochemistry, and ultimately, human health.

Although lakes make up only about 3% of Earth’s land surface, they contain a disproportionate concentration of the planet’s biodiversity. Lead author Stephen F. Jane, who completed his Ph.D. with Rose, said the changes are concerning both for their potential impact on freshwater ecosystems and for what they suggest about environmental change in general.

“Lakes are indicators or ‘sentinels’ of environmental change and potential threats to the environment because they respond to signals from the surrounding landscape and atmosphere. We found that these disproportionally more biodiverse systems are changing rapidly, indicating the extent to which ongoing atmospheric changes have already impacted ecosystems,” Jane said.

Watch a video about this research.

Although widespread losses in dissolved oxygen across the studied lakes are linked to climate change, the path between warming climate and changing freshwater oxygen levels is driven by different mechanisms between surface and deep waters.

Deoxygenation of surface waters was mostly driven by the most direct path: physics. As surface water temperatures increased by .38 degrees Centigrade per decade, surface water dissolved oxygen concentrations declined by .11 milligrams per liter per decade.

“Oxygen saturation, or the amount of oxygen that water can hold, goes down as temperatures go up. That’s a known physical relationship and it explains most of the trend in surface oxygen that we see,” said Rose.

However, some lakes experienced simultaneously increasing dissolved oxygen concentrations and warming temperatures. These lakes tended to be more polluted with nutrient-rich runoff from agricultural and developed watersheds and have high chlorophyll concentrations. Although the study did not include phytoplankton taxonomic measurements, warm temperatures and elevated nutrient content favor cyanobacteria blooms, whose photosynthesis is known to cause dissolved oxygen supersaturation in surface waters.

“The fact that we’re seeing increasing dissolved oxygen in those types of lakes is potentially an indicator of widespread increases in algal blooms, some of which produce toxins and are harmful. Absent taxonomic data, however, we can’t say that definitively, but nothing else we’re aware of can explain this pattern,” Rose said.

The loss of oxygen in deeper waters, where water temperatures have remained largely stable, follows a more complex path most likely tied to increasing surface water temperatures and a longer warm period each year. Warming surface waters combined with stable deep-water temperatures means that the difference in density between these layers, known as “stratification,” is increasing. The stronger this stratification, the less likely mixing is to occur between layers. The result is that oxygen in deep waters is less likely to get replenished during the warm stratified season, as oxygenation usually comes from processes that occur near the water surface.

“The increase in stratification makes the mixing or renewal of oxygen from the atmosphere to deep waters more difficult and less frequent, and deep-water dissolved oxygen drops as a result,” said Rose. Water clarity losses were also associated with deep-water dissolved oxygen losses in some lakes. However, there was no overarching decline in clarity across lakes.

Oxygen concentrations regulate many other characteristics of water quality. When oxygen levels decline, bacteria that thrive in environments without oxygen, such as those that produce the powerful greenhouse gas methane, begin to proliferate. This suggests the potential that lakes are releasing increased amounts of methane to the atmosphere as a result of oxygen loss. Additionally, sediments release more phosphorous under low oxygen conditions, adding nutrients to already stressed waters.

“Ongoing research has shown that oxygen levels are declining rapidly in the world’s oceans. This study now proves that the problem is even more severe in fresh waters, threatening our drinking water supplies and the delicate balance that enables complex freshwater ecosystems to thrive,” said Curt Breneman, dean of the School of Science. “We hope this finding brings greater urgency to efforts to address the progressively detrimental effects of climate change.”

“Widespread deoxygenation of temperate lakes” was published with support from the National Science Foundation. Rose and Jane were joined by dozens of collaborators in GLEON, the Global Lake Ecological Observatory Network, and based in universities, environmental consulting firms, and government agencies around the world.

Featured image: Oxygen levels in the world’s temperate freshwater lakes are declining faster than in the oceans. © Gretchen Hansen, University of Minnesota

Reference: Jane, S.F., Hansen, G.J.A., Kraemer, B.M. et al. Widespread deoxygenation of temperate lakes. Nature 594, 66–70 (2021).

Provided by Rensselaer Polytechnic Institute

Study Finds Ghost Forest ‘Tree Farts’ Contribute to Greenhouse Gas Emissions (Ecology)

 emissions from standing dead trees in coastal wetland forests – colloquially called “tree farts” – need to be accounted for when assessing the environmental impact of so-called “ghost forests.”

In the study, researchers compared the quantity and type of GHG emissions from dead tree snags to emissions from the soil. While snags did not release as much as the soils, they did increase GHG emissions of the overall ecosystem by about 25 percent. Researchers say the findings show snags are important for understanding the total environmental impact of the spread of dead trees in coastal wetlands, known as ghost forests, on GHG emissions.

“Even though these standing dead trees are not emitting as much as the soils, they’re still emitting something, and they definitely need to be accounted for,” said the study’s lead author Melinda Martinez, a graduate student in forestry and environmental resources at NC State. “Even the smallest fart counts.”

In the study, researchers measured emissions of carbon dioxide, methane and nitrous oxide from dead pine and bald cypress snags in five ghost forests on the Albemarle-Pamlico Peninsula in North Carolina, where researchers have been tracking the spread of ghost forests due to sea-level rise.

“The transition from forest to marsh from these disturbances is happening quickly, and it’s leaving behind many dead trees,” Martinez said. “We expect these ghost forests will continue to expand as the climate changes.”

Using portable gas analyzers, researchers measured gases emitted by snags and from soils in each forest in 2018 and 2019. Overall average emissions from soils were approximately four times higher than average emissions from snags in both years. And while snags did not contribute as much as soils, researchers said they do contribute significantly to emissions.

In addition to finding that soils emit more GHGs than snags, the work lays the foundation for the researchers’ ongoing work to understand the role snags are playing in emissions – whether they prevent emissions, like corks, or release them like straws. That is an area of future research they’re currently continuing to explore.

“We started off this research wondering: Are these snags straws or corks?” said study co-author Marcelo Ardón, associate professor of forestry and environmental sciences at NC State. “Are they facilitating the release from soils, or are they keeping the gases in? We think that they act as straws, but as a filtered straw. They change those gases, as the gases move through the snags.”

The study, “Drivers of Greenhouse Gas Emissions from Standing Dead Trees in Ghost Forests,” was published online in Biogeochemistry on May 10, 2021. Funding was provided by the National Science Foundation under grant DEB1713592 and a 2019 North Carolina Sea Grant/SpaceGrant Fellowship.

Featured image: Researchers studying “tree farts” from ghost forests in North Carolina. Credit: Melinda Martinez. © NC State

Reference: Melinda Martinez and Marcelo Ardόn, “Drivers of Greenhouse Gas Emissions from Standing Dead Trees in Ghost Forests”, Published online in Biogeochemistry on May 10, 2021. DOI10.1007/s10533-021-00797-5

Provided by NC State

Opinion: Climate Change – How Bad Could the Future Be If We Do Nothing? (Ecology)

Professor Mark Maslin (UCL Geography) lays out two possible futures for the future, one in which the effects of climate change ravage the planet, and one in which we do everything possible to prevent this being the case.

The climate crisis is no longer a looming threat – people are now living with the consequences of centuries of greenhouse gas emissions. But there is still everything to fight for. How the world chooses to respond in the coming years will have massive repercussions for generations yet to be born.

In my book How to Save Our Planet, I imagine two different visions of the future. One in which we do very little to address climate change, and one in which we do everything possible.

This is what the science suggests those very different realities could look like.

Year 2100: the nightmare scenario

The 21st century draws to a close without action having been taken to prevent climate change. Global temperatures have risen by over 4°C. In many countries, summer temperatures persistently stay above 40°C. Heatwaves with temperatures as high as 50°C have become common in tropical countries.

Every summer, wildfires rage across every continent except Antarctica, creating plumes of acrid smoke that make breathing outdoors unbearable, causing an annual health crisis.

Ocean temperatures have risen dramatically. After repeated bleaching events, Australia’s Great Barrier Reef has been officially declared dead.

Frequent and prolonged droughts torment vast swathes of the Earth’s land. The deserts of the world have expanded, displacing many millions of people. Around 3.5 billion live in areas where water demand exceeds what’s available.

Air pollution has a new major cause outside the traffic-choked cities: dust whipped up from now-barren farmland.

The Arctic is free of sea ice every summer. Average temperatures in the far north have risen by over 8°C as a result. The Greenland and Western Antarctic ice sheets have started to melt, releasing a huge amount of freshwater into the oceans.

Most mountain glaciers have completely melted. Skiing is now a predominantly indoor sport which takes place on giant artificial slopes. Most of the Himalayan plateau’s ice has disappeared, reducing the flows of the Indus, Ganges, Brahmaputra and Yamuna rivers which over 600 million people rely on for plentiful water.

The extra heat in the ocean has caused it to expand. Combined with water from melting ice sheets, sea levels have risen by more than one metre. Many major cities, including Hong Kong, Rio de Janeiro and Miami, are already flooded and uninhabitable. The Maldives, the Marshall Islands, Tuvalu and many other small island nations have been abandoned.

Many coastal and river areas are regularly flooded, including the Nile Delta, the Rhine valley and Thailand. Over 20% of Bangladesh is permanently under water.

Winter storms are more energetic and unleash more water, causing widespread wind damage and flooding each year.

Tropical cyclones have become stronger and affect tens of millions of people every year. Mega-cyclones, like 2013’s Typhoon Haiyan, have become more common, with sustained wind speeds of over 200 mph.

South-east Asian monsoons have become more intense and unpredictable, bringing either too much or too little rain to each region, affecting the lives of over three billion people.

Food and water insecurity has increased around the world, threatening the health and wellbeing of billions of people. Extreme heat and humidity in the tropics and subtropics has increased the number of days that it is impossible to work outside tenfold – slashing farm productivity. Extreme weather in temperate regions like Europe has made food production highly unpredictable. Half of the land devoted to agriculture in the past is now unusable, and the capacity of the rest to grow food differs widely from season to season. Crop yields are at their lowest levels since the middle of the 20th century.

Fish stocks have collapsed. The acidity of the ocean has increased by 125%. The ocean food chain has collapsed in some regions as the small marine organisms that form its base struggle to make calcium carbonate shells and so survive in the more acidic waters.

Despite advances in medical sciences, deaths from tuberculosis, malaria, cholera, diarrhoea and respiratory illnesses are at their highest levels in human history. Extreme weather events – from heat waves and droughts to storms and floods – are causing large loss of life and leaving millions of people homeless. Disease epidemics have plagued the century, spreading among populations beleaguered by widespread poverty and vulnerability.

Year 2100: humanity rises to the challenge

This is what our planet could look like if we do everything in our power to contain climate change.

Global temperatures rose to 1.5°C by 2050 and remained there for the rest of the century. Fossil fuels have been replaced by renewable energy. Over a trillion trees have been planted, sucking carbon dioxide from the atmosphere. The air is cleaner than it has been since before the industrial revolution.

Cities have been restructured to provide all-electric public transport and vibrant green spaces. Many new buildings have a photoelectric skin which generates solar energy and green roofs which cool the cities, making them a more pleasant place to live. High-speed electric trains reaching 300 mph link many of the world’s major cities. Intercontinental flights still run, using large and efficient planes running on synthetic kerosene that’s made by combining water and carbon dioxide sucked directly from the atmosphere.

Vegetation covers the exterior of a building in a Japanese city.

Global diets have shifted away from meat. Farming efficiency has greatly improved during the transition from industrial-scale meat production to plant-based sustenance, creating more land to rewild and reforest.

Half of the Earth is dedicated to restoring the natural biosphere and its ecological services. Elsewhere, fusion energy is finally set to work at scale providing unlimited clean energy for the people of the 22nd century.

Two very different futures. The outcome your children and grandchildren will live with depends on what decisions are made today. Happily, the solutions I propose are win-win, or even win-win-win: they reduce emissions, improve the environment and make people healthier and wealthier overall.

This article was originally published in The Conversation on 06 May 2021.

Featured image: Mark Maslin © UCL

Provided by University College of London

Mangroves and Seagrasses Absorb Microplastics (Ecology)

Microplastics do not just end up in the open sea – in fact, a lot also end up in the ecosystems of the coastal zones, a new study shows and this may threaten wildlife.

Mangroves and seagrasses grow in many places along the coasts of the world, and these ‘blue forests’ constitute an important environment for a large number of animals. Here, juvenile fish can hide until they are big enough to take care of themselves; crabs and mussels live on the bottom; and birds come to feed on the plants.

However, the plant-covered coastal zones do not only attract animals but also microplastics, a new study shows.

– The denser the vegetation, the more plastic is captured, says Professor and expert in coastal ecology, Marianne Holmer, from the University of Southern Denmark.

The animals eat plastic

She is concerned about how the accumulated microplastics affect animal and plant life.

– We know from other studies that animals can ingest microplastics and that this may affect their organism.

Animals ingest microplastics with the food they seek in the blue forests. They may suffocate, die of starvation, or the small plastic particles can get stuck different places in the body and do damage.

May spread disease

Another problem with microplastics is that they may be covered with microorganisms, environmental toxins or other health hazardous/disease-promoting substances that are transferred to the animal or plant that absorbs the microplastics.

– When microplastics are concentrated in an ecosystem, the animals are exposed to very high concentrations, Marianne Holmer explains.

She points out that microplastics concentrated in, for example, a seagrass bed are impossible to remove again.

Worst in the mangrove forests

The study is based on examinations of three coastal areas in China, where mangroves, Japanese eelgrass (Z. japonica) and the paddle weed Halophila ovalis grow. All samples taken in blue forests had more microplastics than samples from control sites without vegetation.

The concentrations were up to 17.6 times higher, and they were highest in the mangrove forest. The concentrations were up to 4.1 times higher in the seagrass beds.

Mangrove trees probably capture more microplastics, as the capture of particles is greater in mangrove forests than in seagrass beds.

“It’s my expectation that we will also find higher concentrations of microplastics in Danish and global seagrasses.”

— Marianne Holmer, Professor

Researchers also believe that microplastics bind in these ecosystems in the same way as carbon; the particles are captured between leaves and roots, and the microplastics are buried in the seabed.

– Carbon capture binds carbon dioxide in the seabed, and the blue forests are really good at that, but it’s worrying if the same thing happens to microplastics, says Marianne Holmer.

Although the study was conducted along Chinese coasts, it may be relevant to similar ecosystems in the rest of the world, including Denmark, where eelgrass beds are widespread.

– It’s my expectation that we will also find higher concentrations of microplastics in Danish and global seagrasses, she says.

The study was conducted in collaboration with colleagues from the Zhejiang University in China, among others, and is published in the journalEnvironmental Science and Technology.

Featured image: Many animals live in seagrass beds and are thus exposed to microplastic. © Troels Lange/SDU.

Reference: Yuzhou Huang, Xi Xiao*, Kokoette Effiong, Caicai Xu, Zhinan Su, Jing Hu, Shaojun Jiao, and Marianne Holmer, “New Insights into the Microplastic Enrichment in the Blue Carbon Ecosystem: Evidence from Seagrass Meadows and Mangrove Forests in Coastal South China Sea”, Environ. Sci. Technol. 2021, 55, 8, 4804–4812
Publication Date:March 11, 2021

Provided by University of Southern Denmark

Young Male Fruit Flies Make Females Fight Each Other More (Ecology)

Mating changes female behaviour across a wide range of animals, with these changes induced by components of the male ejaculate, such as sperm and seminal fluid proteins. However, males can vary significantly in their ejaculates, due to factors such as age, mating history, or feeding status. This male variation may therefore lead to variation in the strength of responses males can stimulate in females.

Using the fruit fly, Drosophila melanogaster, we tested whether age, mating history, and feeding status shape an important, but understudied, post-mating response – increased female-female aggression.

Image 1: Two female fruit flies are standing on a food cap (which contains food that they eat and lay eggs in). This is where the majority of fighting happens – you can see the flies have their legs touching, so they are probably fencing in this image. Each fly is marked with a different colour of paint to aid identification. © University of Oxford

We found that females mated to old males fought less than females mated to young males. Females mated to old, sexually active males fought even less than those mated to males who were merely old, but there was no effect of male starvation status on mating-induced female aggression.

Male condition can therefore influence how females interact with each other – who you mate with changes your interactions with members of the same sex! 

Image 2: This figure shows the setup we used for contests between females, which consisted of a circular arena with a food cap set into the middle. This food cap contained regular fly food medium, with a drop of yeast paste in the middle to act as a valuable, restricted resource. © University of Oxford

Could this happen in other species?

We know that other species (including humans!) have proteins in the seminal fluid that males transfer to females during sex. Various of these proteins have effects on female physiology and behaviour, but no one knows if these affect aggression (in humans or any other species).

We also know that male age (in flies and humans) results in reduced fertility and can have serious effects on their offspring. Although it is a long leap from flies to humans, could who you mate with influence your interactions with other females?

Many reproductive molecules and important bodily functions are conserved across the animal kingdom from flies to humans, so it is possible that what we found in flies here might be hinting to a common phenomenon across the tree of life. We need more studies to understand if this is the case!

Read the full paper, ‘Male condition influences female post mating aggression and feeding in Drosophila‘ in Functional Ecology.

Provided by University of Oxford

The Way A Fish Swims Reveals A Lot About Its Personality (Ecology)

Personality has been described in all sorts of animal species, from ants to apes. Some individuals are shy and sedentary, while others are bold and active. Now a new study published in Ecology and Evolution has revealed that the way a fish swims tells us a lot about its personality.

This new research suggests experts can reliably measure animal personality simply from the way individual animals move, a type of micropersonality trait, and that the method could be used to help scientists understand about personality differences in wild animals.

A team of biologists and mathematicians from Swansea University and the University of Essex filmed the movements of 15 three-spined stickleback fish swimming in a tank which contained two, three, or five plastic plants in fixed positions.

Using the high‐resolution tracking data from video recordings, the team took measurements of how much and how often the fish turned, and how much they stopped and started moving.

The data revealed that each fish’s movements were very different, and that these differences were highly repeatable – so much so that the researchers could identify a fish just from its movement data. 

Dr Ines Fürtbauer, a co-author of the study from Swansea University, said: “These micropersonalities in fish are like signatures – different and unique to an individual. We found the fish’s signatures were the same when we made simple changes to the fish tanks, such as adding additional plants. However, it is possible these signatures change gradually over an animal’s lifetime, or abruptly if an animal encounters something new or unexpected in its environment. Tracking animals’ motion over longer periods and in the wild will give us this sort of insight and help us better understand not only personality but also how flexible an animal’s behaviour is.”

The authors of the study say that further work with other species and contexts is needed to see how general the phenomenon is, and if the same patterns are seen with land animals or flying species.  

Dr Andrew King, lead author from Swansea University, said: “Our work suggests that simple movement parameters can be viewed as micropersonality traits that give rise to extensive consistent individual differences in behaviours. This is significant because it suggests we might be able to quantify personality differences in wild animals as long as we can get fine-scale information on how they are moving; and these types of data are becoming more common with advances in animal tracking technologies.”

Featured image: A three-spine stickleback fish swimming in the tank © Swansea University

Read “Micropersonality” traits and their implications for behavioral and movement ecology research on Ecology and Evolution.

Provided by Swansea University

Pioneering Research Reveals Gardens Are Secret Powerhouse for Pollinators (Ecology)

Home gardens are by far the biggest source of food for pollinating insects, including bees and wasps, in cities and towns, according to new research published in the Journal of Ecology.

The study, led by the University of Bristol and published today in the Journal of Ecology, measured for the first time how much nectar is produced in urban areas and discovered residential gardens accounted for the vast majority – some 85 per cent on average.

Results showed three gardens generated daily on average around a teaspoon of Nature’s ambrosia, the unique sugar-rich liquid found in flowers which pollinators drink for energy. While a teaspoon may not sound much to humans, it’s the equivalent to more than a tonne to an adult human and enough to fuel thousands of flying bees. The more bees and fellow pollinators can fly, the greater diversity of flora and fauna will be maintained.

Residential gardens underpin the urban nectar supply, and many can be extremely rich in flowering plants. Credit: Nicholas Tew.

Ecologist Nicholas Tew, lead author of the study, said: “Although the quantity and diversity of nectar has been measured in the countryside, this wasn’t the case in urban areas, so we decided to investigate.

“We expected private gardens in towns and cities to be a plentiful source of nectar, but didn’t anticipate the scale of production would be to such an overwhelming extent. Our findings highlight the pivotal role they play in supporting pollinators and promoting biodiversity in urban areas across the country.”

The research, carried out in partnership with the universities of Edinburgh and Reading and the Royal Horticultural Society, examined the nectar production in four major UK towns and cities: Bristol, Edinburgh, Leeds, and Reading. Nectar production was measured in nearly 200 species of plant by extracting nectar from more than 3,000 individual flowers. The extraction process involves using a fine glass tube. The sugar concentration of the nectar was quantified with a refractometer, a device which measures how much light refracts when passing through a solution.

“We found the nectar supply in urban landscapes is more diverse, in other words comes from more plant species, than in farmland and nature reserves, and this urban nectar supply is critically underpinned by private gardens,” said Nicholas Tew, who is studying for a PhD in Ecology.

“Gardens are so important because they produce the most nectar per unit area of land and they cover the largest area of land in the cities we studied.”

Nearly a third (29 per cent) of the land in urban areas comprised domestic gardens, which is six times the area of parks, and 40 times the area of allotments.

Bees comprise a small proportion of the pollinator species found in the UK. Others include moths (TL), beetles (TR), hoverflies (BR) and sawflies (BL).. Credit: Nicholas Tew.

“The research illustrates the huge role gardeners play in pollinator conservation, as without gardens there would be far less food for pollinators, which include bees, wasps, butterflies, moths, flies, and beetles in towns and cities. It is vital that new housing developments include gardens and also important for gardeners to try to make sure their gardens are as good as possible for pollinators,” Nicholas Tew explained.

“Ways to do this include planting nectar-rich flowers, ensuring there is always something in flower from early spring to late autumn, mowing the lawn less often to let dandelions, clovers, daisies and other plant flowers flourish, avoiding spraying pesticides which can harm pollinators, and avoiding covering garden in paving, decking or artificial turf.”

Dr Stephanie Bird, an entomologist at the Royal Horticultural Society, which helped fund the research, said: “This research highlights the importance of gardens in supporting our pollinating insects and how gardeners can have a positive impact through their planting decisions. Gardens should not be seen in isolation – instead they are a network of resources offering valuable habitats and provisions when maintained with pollinators in mind.”

Featured image: Even balconies and window boxes in densely urban regions can provide food for pollinators. Credit: Nicholas Tew.

You can read the full open access article here:

‘Quantifying nectar production by flowering plants in urban and rural landscapes’ by N.E.Tew et al in Journal of Ecology

Provided by British Ecological Society

Research Reveals Why Plant Diversity Is So Important For Bee Diversity (Ecology)

Delicate balance of energy efficiency and flower morphology are key to co-existence between honey bees and bumble bees

As abundant and widespread bees, it is common to see both bumble bees and honey bees foraging on the same flower species during the summer, whether in Britain or many other countries.

Yet researchers at the Laboratory of Apiculture and Social Insects (LASI) at the University of Sussex, have found that different bees dominate particular flower species and revealed why.

By studying 22 flower species in southern England and analysing the behaviour of more than 1000 bees, they found that ‘energy efficiency’ is a key factor when it comes to mediating competition.

Bee bodyweight and the rate at which a bee visits flowers determine how energy efficient they are. Bodyweight determines the energy used while flying and walking between flowers, with a bee that is twice as heavy using twice as much energy. The rate at which a bee visits flowers, the number of flowers per minute, determines how much nectar, and therefore energy, it collects. Together, the ratio of these factors determines bee foraging energy efficiency.

Professor of Apiculture, Francis Ratnieks, said: “While they forage on the same flowers, frequently we find that bumble bees will outnumber honey bees on a particular flower species, while the reverse will be true on a different species growing nearby.

“What was remarkable was that differences in foraging energy efficiency explained almost fully why bumble bees predominated on some flower species and honey bees on others.

A honey bee on a lavender plant, one of the species studied in the research © Professor Francis Ratnieks, University of Sussex

“In essence, bumble bees have an advantage over honey bees in being faster at visiting flowers, so can gather more nectar (energy), but a disadvantage in being larger, and so using more of the nectar energy to power their foraging. On some flower species this gave an overall advantage to bumble bees, but on others to honey bees.”

In the study, published in the journal Ecology, the researchers used stopwatches to determine how many flowers a bee visited in one minute. Using a portable electronic balance to weigh each bee, researchers found that, on average, bumble bees are almost twice as heavy as the honey bees. This means that they use almost twice as much energy as honey bees. The stopwatch results showed that they visit flowers at twice the rate of honey bees, which compensate in terms of energy efficiency.

On some flower species such as lavender, where bumble bees dominated, visiting flowers at almost three times the rate of honeybees.

The differences in the morphology of flowers impacted greatly on how energy efficient the two bee types were. Ling heather, with its mass of small flowers was better suited to the nimbler honey bee. By contrast, Erica heather, which researchers found growing beside the ling heather in the same nature reserve, has large bell shaped flowers and was better suited to bumble bees.

Author Dr Nick Balfour said: “The energy efficiency of foraging is particularly important to bees. The research showed that the bees were walking (and flying) a challenging energy tightrope; half the energy they obtained from the nectar was expended in its collection.”

Energy (provided by nectar for bees) is a fundamental need, but the fact that honey bees and bumble bees do not compete head on for nectar is reassuring in terms of conservation and co-existence.

Prof Ratnieks explained: “Bumble bees have a foraging advantage on some plants, and predominate on them, while honey bees have an advantage on others and predominate on these.

“Bee conservation therefore benefits from flower diversity, so that should certainly be a focus on bee conservation efforts. But fortunately, flowering plants are diverse.”

The research team, which included Sussex PhD student Kyle Shackleton, Life Sciences undergraduates Natalie A. Arscott, Kimberley Roll-Baldwin and Anthony Bracuti, and Italian volunteer, Gioelle Toselli, studied flower species in a variety of local locations. This included a nature reserve, the wider countryside, Brighton parks, Prof Ratnieks’s own garden and a flower bed outside Sussex House on the University campus.

Dr Balfour said: “Whether you have a window box, allotment or a garden, planting a variety of summer-blooming flowers or cutting your grass less often can really help pollinators during late summer.”

Featured image: A bumble bee pictured on a lavender plant, one of the species studied. © Prof Francis Ratnieks, University of Sussex

Reference: Balfour, N.J., Shackleton, K., Arscott, N.A., Roll‐Baldwin, K., Bracuti, A., Toselli, G. and Ratnieks, F.L. (2021), Energetic efficiency of foraging mediates bee niche partitioning. Ecology. Accepted Author Manuscript e03285.

Provided by University of Sussex