Bees ‘betray’ their flowers when pollinator species decline

The findings suggest that "global declines in pollinators could have a bigger impact on flowering plants and foods than previously realized," says ecologist Berry Brosi.

By Carol Clark

Remove even one bumblebee species from an ecosystem and the impact is swift and clear: Their floral “sweethearts” produce significantly fewer seeds, a new study finds.

The study, to be published by the Proceedings of the National Academy of Sciences, focused on the interactions between bumblebees and larkspur wildflowers in Colorado’s Rocky Mountains. The results show how reduced competition among pollinators disrupts floral fidelity, or specialization, among the remaining bees in the system, leading to less successful plant reproduction.

“We found that these wildflowers produce one-third fewer seeds in the absence of just one bumblebee species,” says Emory University ecologist Berry Brosi, who led the study. “That’s alarming, and suggests that global declines in pollinators could have a bigger impact on flowering plants and food crops than was previously realized.”

The National Science Foundation (NSF) funded the study, co-authored by ecologist Heather Briggs of the University of California-Santa Cruz.

About 90 percent of plants need animals, mostly insects, to transfer pollen between them so that they can fertilize and reproduce. Bees are by far the most important pollinators worldwide and have co-evolved with the floral resources they need for nutrition.

During the past decade, however, scientists have reported dramatic declines in populations of some bee species, sparking research into the potential impact of such declines.

Some studies have indicated that plants can tolerate losing most pollinator species in an ecosystem as long as other pollinators remain to take up the slack. Those studies, however, were based on theoretical computer modeling.

Emory University ecologist
Berry Brosi led the study.

Brosi and Briggs were curious whether this theoretical resilience would hold up in real-life scenarios. Their team conducted field experiments to learn how the removal of a single pollinator species would affect the plant-pollinator relationship.

“Most pollinators visit several plant species over their lifetime, but often they will display what we call floral fidelity over shorter time periods,” Brosi explains. “They’ll tend to focus on one plant while it’s in bloom, then a few weeks later move on to the next species in bloom. You might think of them as serial monogamists.”

Floral fidelity clearly benefits plants, because a pollinator visit will only lead to plant reproduction when the pollinator is carrying pollen from the same plant species.  “When bees are promiscuous, visiting plants of more than one species during a single foraging session, they are much less effective as pollinators,” Briggs says.

The experiments were done at the Rocky Mountain Biological Laboratory near Crested Butte, Colorado. Located at 9,500 feet, the facility’s subalpine meadows are too high for honeybees, but they are buzzing during the summer months with bumblebees. The experiments focused on the interactions of the insects with larkspurs, dark-purple wildflowers that are visited by 10 of the of the 11 bumblebee species there.

Watch a video about the Rocky Mountain Biological Laboratory: 

 
The study included a series of 20-meter square wildflower plots. Each was evaluated in a control state, left in its natural condition, and in a manipulated state, in which bumblebees of just one species had been removed using nets.

“We’d literally follow around the bumblebees as they foraged,” Briggs says, describing how they observed the bee behavior. “It’s challenging because the bees can fly pretty fast.”

Sometimes the researchers could only record between five and 10 movements, while in other cases they could follow the bees to 100 or more flowers.

“Running around after bumblebees in these beautiful wildflower meadows was one of the most fun parts of the research,” Brosi says. Much of this “bee team” was made up of Emory undergraduate students, funded by the college’s Scholarly Inquiry and Research at Emory (SIRE) grants and NSF support via the Research Experience for Undergraduates (REU) program.

The Rocky Mountain Biological Laboratory is exacting about using non-destructive methodologies so that researchers don’t have a negative impact on the bumblebee populations. “When we caught bees to remove target species from the system, or to swab their bodies for pollen, we released them unharmed when our experiments were over,” Brosi says. “They’re very robust little creatures.”

No researchers were harmed either, he adds. “Stings were very uncommon during the experiments. Bumblebees are quite gentle on the whole.”

Across the steps of the pollination process, from patterns of bumblebee visits to plants, to picking up pollen, to seed production, the researchers saw a cascading effect of removing one bee species. While about 78 percent of the bumblebees in the control groups were faithful to a single species of flower, only 66 percent of the bumblebees in the manipulated groups showed such floral fidelity. The reduced fidelity in manipulated plots meant that bees in the manipulated groups carried more different types of pollen on their bodies than those in the control groups.

These changes had direct implications for plant reproduction: Larkspurs produced about one-third fewer seeds when one of the bumblebee species was removed, compared to the larkspurs in the control groups.

“The small change in the level of competition made the remaining bees more likely to ‘cheat’ on the larkspur,” Briggs says.

While previous research has shown how competition drives specialization within a species, the bumblebee study is one of the first to link this mechanism back to the broader functioning of an ecosystem.

“Our work shows why biodiversity may be key to conservation of an entire ecosystem,” Brosi says. “It has the potential to open a whole new set of studies into the functional implications of interspecies interactions.”

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Why the future of fuel lies in artificial photosynthesis

By Carol Clark

Most people, especially technical experts, may agree that we have an energy crisis, but it’s much harder to come to a consensus on how to solve it.

Fossil fuels, wind power, biofuels, geothermal power, nuclear energy and solar power are all pieces in the puzzle for how to keep Earth’s burgeoning civilization running, says Emory inorganic chemist Craig Hill.

He adds, however, that an energy source that will be essential to manage the crisis in the coming decades is the least developed: Artificial photosynthesis.

Hill and other top experts in the nascent field of artificial photosynthesis co-wrote an opinion piece on the topic published in the journal Energy and Environmental Science.

“Humanity is on the threshold of a technological revolution that will allow all human structures across the earth to undertake photosynthesis more efficiently than plants,” the authors write.

The 18 authors on the opinion piece, from leading research universities and national laboratories in the United States, Europe and Australia, represent the broad range of expertise, from chemistry to biology to engineering, working on the problem.

The aim of artificial photosynthesis is to use solar energy to split water, to generate hydrogen as a cheap and abundant source of carbon-free fuel.

“The development and global deployment of such artificial photosynthesis (AP) technology,” the authors write, “addresses three of humanity’s most urgent public policy challenges: to reduce anthropogenic carbon dioxide emissions, to increase fuel security and to provide a sustainable global economy and ecosystem. Yet, despite the considerable research being undertaken in this field … AP remains largely unknown in energy and climate change public policy debates.”

“Globally, our energy requirements our expected to double in the next 30 to 40 years, maybe less,” Hill says. “It’s a staggering problem that puts everything else in perspective. Everything derives from energy. If we don’t have enough energy, we’re not going to have enough food and water.”

Fracking has opened up new sources of fossil fuels in the United States, but ultimately fossil fuels are going to run out. Fossil fuel use is also coming at a rapidly escalating environmental cost, including rising global temperatures and acidification of the oceans.

The only energy source that can come close to sustainably powering our long-term needs is terrestrial sunlight, Hill says.

The solar power industry, which converts sunlight into electricity, continues to grow, but it has severe limitations, Hill says. A great deal of space is required for solar panels to collect the sun’s energy, and that energy must be stored in batteries.

“We’re at the point now where we have solar powered buildings and electric cars, but we are never going to be able to run airplanes and ships and most other forms of transportation on electricity,” Hill says. “That’s why we ultimately need artificial photosynthesis, which is just another way of saying solar fuel.”

The goal of artificial photosynthesis is to do what plants do, only better.

“Plants use sunlight, water and carbon dioxide to make fuel in the form of carbohydrates,” Hill explains. “The process, however, is incredibly inefficient. It works for plants because they don’t have to worry about finances.”

Scientists currently know how to mimic plant photosynthesis, but not in ways that are powerful and efficient enough for practical application. Breakthroughs are needed in both fundamental science and materials engineering, says Hill, who is working on perfecting a key aspect of the problem, a water oxidation catalyst. Hill’s lab has developed the fastest homogeneous water oxidation catalyst to date.

“Artificial photosynthesis is a tremendous challenge,” Hill says, “but it’s also tremendously exciting.”

Hill foresees that we will eventually make the necessary breakthroughs to generate solar fuel. We simply have no other choice, he adds, as the human population approaches 10 billion by 2050.

Meanwhile, Hill and the co-authors of the Energy and Environmental Science opinion piece are calling for a globalized approach to artificial photosynthesis, to help raise the field’s public policy profile, remove logistical and governmental hurdles to its development, and strengthen an international commitment to clean, sustainable energy.

They envision scenarios like a network of light capture facilities situated in coastal cities where seawater would be catalytically converted to hydrogen and oxygen.

“Photosynthesis is the great invention of life,” they write. “Like biodiversity, the atmosphere, the moon, outer-space, the human genome and the world’s cultural and natural heritage, it could be treated as subject to common heritage requirements under international law, perhaps through a specific UN or UNESCO declaration. Common heritage of humanity status putatively limits private or public appropriation; requires representatives from all nations to manage such resources on behalf of all, actively share the benefits, restrain from their militarization and preserve them for the benefit of future generations.”

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Images: iStockphoto.com

A voice for the science of sustainability

Emory anthropologist Peggy Barlett studies the intersection of economic, ecological and demographic change among farmers around the world. She is also a key player in moving higher education to the forefront of sustainability.

“There are so many ways that our culture right now is in transition,” she says. “As an anthropologist I see a whole shift in the challenges we face and the ways in which universities, governments and faith communities are trying to contribute. Higher education has so many tools and so many talents to offer, I think it’s incredibly important to make sure that what we know is available to the general public.”

Barlett is part of the Public Voices Thought Leadership Fellowship at Emory. A collaboration with The OpEd Project, the program is designed to cultivate a sense of social responsibility and to increase the number of women involved in public debate. Check out the web site of the program’s lead sponsor, the Center for Women at Emory, to learn more.

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A taste of traditional Italian medicine

Medical Ethnobotanist Cassandra Quave collecting plant specimens in Italy.

By Carol Clark

“Ethnobotany is the science of survival,” Cassandra Quave told a group of Emory students when they visited her field research site in southern Italy recently.

Quave, a medical ethnobotantist with Emory’s Center for the Study of Human Health, is documenting the traditional ways that people use plants in the Vulture-Alto Bradano region of Basilicata province, a landscape of rolling hillsides dominated by the dormant volcano Monte Vulture. She is also collecting specimens of medicinal plants that she will take back to her Emory lab for her drug discovery research projects.

The students were in Italy this June as part of the “Italian and Medical Humanities” course, a collaboration of Emory’s Italian Studies Program, the School of Medicine, the Center for Ethics and the Center for the Study of Human Health.

Their itinerary included a day with Quave, who immersed the students in the local life of the village of Ginestra. She took them on a walk through the surrounding countryside, identifying the traditional medicinal uses of plants they encountered along the way. A fourth-generation shepherd told the students about pastoral life, and truffle hunters demonstrated how they use dogs to hunt these gourmet delicacies.

Cassandra Quave takes students off the beaten track, to learn about agrarian life.

“The students got to see first-hand how important traditional knowledge of environmental resources can be to a community,” Quave says. “It would be very difficult for these people to survive without it.”

During a visit to a vineyard, Quave made a point of having the students pick and eat ripe mulberries off a tree. “Today, especially in the U.S., people are very disconnected from their environment and food sources,” she says. “For many of the students, this was the first time that they had ever eaten anything that they had harvested themselves.”

Basilicata is home to the Arbereshe ethnic minority in Italy, the descendants of Albanians who fled the Ottoman invasion of Albania five centuries ago. “They have maintained their language, which is very different from modern-day Albanian, and adapted to a new environment, while still keeping some of their homeland traditions alive,” Quave says. “Unfortunately, many of these practices are in a state of rapid decline. The Arbereshe language is listed as an endangered language and as the language disappears, so does much of the culture.”

Quave currently has a $1.8 million grant from the National Institutes of Health to pursue her research into how an extract from the elm leaf blackberry, a tree common in forests across Europe, might help fight antibiotic-resistant staph. Click here to read more about her research.

Here are more photos of the students in Basilicata. 

Photos courtesy of Cassandra Quave.

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Freshman friendship fuels bio-tech business

Watch a TEDxAtlanta talk by Solazyme co-founder Harrison Dillon, above.

Diane Cardwell wrote a feature for the New York Times about Solazyme, a company founded by two Emory grads who are using algae to create clean fuel and other products. Here’s an excerpt from the article:

"Starting when they became friends in freshman year at Emory University in Atlanta, Jonathan S. Wolfson and Harrison F. Dillon would take off into the mountains of Wyoming and Colorado for weeks at time. They spent their days hiking in the wilderness and their nights drinking bourbon by the campfire, talking big about how one day they would build a company that would help preserve the environment they both loved.

"They graduated, and the backpacking trips grew shorter and further between. Mr. Dillon went on to earn a PhD in genetics and a law degree, and ended up working as a biotech patent lawyer in Silicon Valley. Mr. Wolfson received law and business degrees from New York University and eventually started a software business. But the two still got together every year. And they kept talking about the company that, they imagined as time went on, would use biotechnology to create renewable energy."

Read the whole article in The New York Times.

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