Worldwide Importance Of Honey Bees For Natural Habitats Captured In New Report

UC San Diego News Center     By Mario Aguilera     January 10, 2018

Global synthesis of data reveals honey bees as world's key pollinator of non-crop plants

Non-native honey bees crowding at a flower of the native coast pricklypear cactus (Opuntia littoralis) in Southern California. Credit: James Hung/UC San DiegoAn unprecedented study integrating data from around the globe has shown that honey bees are the world’s most important single species of pollinator in natural ecosystems and a key contributor to natural ecosystem functions. The first quantitative analysis of its kind, led by biologists at the University of California San Diego, is published Jan. 10 in Proceedings of the Royal Society B.

The report weaves together information from 80 plant-pollinator interaction networks. The results clearly identify the honey bee (Apis mellifera) as the single most frequent visitor to flowers of naturally occurring (non-crop) plants worldwide. Honey bees were recorded in 89 percent of the pollination networks in the honey bee’s native range and in 61 percent in regions where honey bees have been introduced by humans.

One out of eight interactions between a non-agricultural plant and a pollinator is carried out by the honey bee, the study revealed. The honey bee’s global importance is further underscored when considering that it is but one of tens of thousands of pollinating species in the world, including wasps, flies, beetles, butterflies, moths and other bee species.

“Biologists have known for a while that honey bees are widespread and abundant—but with this study, we now see in quantitative terms that they are currently the most successful pollinators in the world,” said Keng-Lou James Hung, who led the study as a graduate student in UC San Diego’s Division of Biological Sciences. He’s now a postdoctoral researcher at the Ohio State University.

The proportion of all floral visits contributed by the western honey bee in 80 plant-pollinator interaction networks in natural habitats worldwide. Honey bees are generally considered a native species in Europe, the Middle East and Africa, and introduced elsewhere.Honey bees are native to Africa, the Middle East and Southern Europe and have become naturalized in ecosystems around the world as a result of intentional transport by humans. While feral honey bee populations may be healthy in many parts of the world, the researchers note that the health of managed honey bee colonies is threatened by a host of factors including habitat loss, pesticides, pathogens, parasites and climate change.

“Although they appear to have a disproportionate impact on natural ecosystems, surprisingly we understand very little about the honey bee’s ecological effects in non-agricultural systems,” said study coauthor David Holway, a professor and chair of the Section of Ecology, Behavior and Evolution in Biological Sciences. “Looking to the future this study raises a lot of new questions.”

For instance, in San Diego, where honey bees are not native, they are responsible for 75 percent of pollinator visits to native plants, the highest honey bee dominance in the set of networks examined for any continental site in the introduced range of the honey bee. This is despite the fact that there are more than 650 species of native bees in San Diego County as well as many other native pollinating insects.

“The consequences of this phenomenon for both native plants that did not evolve with the honey bee and for populations of native insect pollinators is well worth studying,” said Joshua Kohn, the study’s senior author.

“Our study also nicely confirms something that pollination biologists have known for a long time: even in the presence of a highly abundant species that pollinates many plant species, we still need healthy populations of other pollinators for entire plant communities to receive adequate pollination services,” said Hung.

A honey bee pollinates a Carpobrotus edulis plant. The photo was taken by James Hung during field work on plant-pollinator interactions in scrub habitats in San Diego. Credit: James Hung/UC San Diego

The reason for this, Hung noted, is that in habitats where honey bees are present, they nevertheless fail to visit nearly half of all animal-pollinated plant species, on average.

“Our take home message is that while it’s important for us to continue to research how we can improve the health of managed honey bee colonies for agricultural success, we need to further understand how this cosmopolitan and highly successful species impacts the ecology and evolutionary dynamics of plant and pollinator species in natural ecosystems,” said Hung.

Coauthors of the study include Jennifer Kingston of UC San Diego and Matthias Albrecht of Agroecology and Environment, Agroscope, Reckenholzstrasse, in Switzerland.

Funding for the study included a National Science Foundation Doctoral Dissertation Improvement Grant (DEB-1501566); a Mildred E. Mathias Graduate Student Research Grant and an Institute for the Study of Ecological and Evolutionary Climate Impacts Graduate Fellowship from the University of California Natural Reserve System; a Frontiers of Innovation Scholar Fellowship, an Academic Senate Grant and a McElroy Fellowship from UC San Diego; a Sea and Sage Audubon Society Bloom-Hays Ecological Research Grant; and a California Native Plants Society Educational Grant.

Why 'Whispers' Among Bees Sometimes Evolve into 'Shouts'

The following is brought to us by the American Bee Journal    July 7, 2014

Let's say you're a bee and you've spotted a new and particularly lucrative source of nectar and pollen. What's the best way to communicate the location of this prize cache of food to the rest of your nestmates without revealing it to competitors, or "eavesdropping" spies, outside of the colony?

Many animals are thought to deter eavesdroppers by making their signals revealing the location or quality of resources less conspicuous to outsiders. In essence, they've evolved "whispers" in their signals to counter eavesdropping.

But some species of bees in Brazil do the exact opposite. "Shouts" in their food-recruitment signals warn would-be competitors that their prime source of food will be fiercely defended if they show up to the site. It's a communication strategy that's bold and risky, yet remarkably successful in warding off competitors, according to a paper published in the July 7 issue of the journal Current Biology.

"It's a signal with honest aspects and the possibility of lies," explains James Nieh, a professor of biology at UC San Diego who oversaw the research study conducted in Brazil by Elinor Lichtenberg, a PhD student in his laboratory who is now a postdoctoral researcher at Washington State University. "It tells nestmates where to find good food and hints at a larger occupying force."

Lichtenberg says her discovery of this counterintuitive method of communication by bees suggests that eavesdroppers can alter the evolution of animal signals in ways that were previously not thought possible.

"Our study provides a new way of looking at how eavesdroppers affect the evolution of animal communication signals," she adds. "Until now, it was thought that eavesdroppers select against conspicuous signals, for example by more easily finding and eating prey that sings loudly. But our results show that eavesdroppers can help select for the same conspicuous signals that are easiest for intended recipients to detect and understand."

To Nieh, whose research has focused on the evolution of communication strategies among bees, "eavesdropping is part of the information web, the signals and cues that surround animals and play a key role in shaping ecosystems."

In the case of bees and other pollinators, he says, "a network of signals and cues shapes pollination, informing animals about where and when food is available. Researchers have in general thought about eavesdropping as a force that makes signals less conspicuous, leading to the evolution of 'whispers' to counter spying. However, we show that eavesdropping can also lead to 'shouts.' In this stingless bee system, with aggressive colonies jockeying for limited resources, more conspicuous food-recruitment signals indicate a higher likelihood that a resource will be harder to wrest away."

Lichtenberg's study focused on stingless bees—including two from the genus Trigona that recruit nestmates to food sources with chemically distinct pheromones—that compete with one another for similar food sources. Trigona hyalinata spies that detect food sources marked by Trigona spinipes foragers will often displace T. spinipes from desirable sites in the wild if they can recruit sufficient nestmates. But Lichtenberg found in a controlled field study that the eavesdropping species will avoid desirable sources of food that have been visited frequently by T. spinipes (communicated by the larger number of pheromone markings at the site) to avoid being attacked. However, T. hyalinata foragers are attracted to food sources with fewer T. spinipes foragers.

The eavesdroppers could take over the highly visited sites by recruiting more of their nestmates or battling with T. spinipes bees, which show high levels of aggression toward intruders, but the risks and energy costs to the eavesdroppers apparently aren't worth the trouble.

The researchers supported this hypothesis by modeling eavesdropping bees' decision-making, using a type of model from economics. They ran the model for T. hyalinata eavesdropping on T. spinipesT. spinipes on T. hyalinata, and the non-aggressive Melipona rufiventris on T. spinipes. In all three cases, they found that the model results matched eavesdropping behavior measured in this study and in previous work by Lichtenberg, Nieh and colleagues.

"Assembling such a group in the nest after having found a food source through eavesdropping uses time and energy the eavesdropper could otherwise spend looking for an unoccupied food source," explains Lichtenberg. "If the eavesdropper brings too small a group to an occupied food source and cannot win access to it, she and the bees accompanying her have essentially wasted energy. For attacks between colonies of the same species, there is also a risk that the conflict will escalate to physical interactions in which large numbers of bees may die."

"Our study is one of the first to investigate what drives the behavior of eavesdroppers collecting information from competitors within the same trophic level, which use the same food resources as the eavesdropper," she adds. "Previous eavesdropping research has mainly focused on individuals seeking mates, predators looking for prey or prey trying to avoid being eaten. In those cases, eavesdroppers' expected behavior is clear. This is not true for eavesdropping on competitors."

The study not only provides information about the evolution of different strategies of animal communication, but suggests how these strategies can affect the ecology of plant communities. "Such strategies affect not only the individuals directly involved, but also broader ecological interactions between the food-gatherers and their food," Lichtenberg says. "This is particularly important for animals such as the bees I studied, because their movements determine plant pollination."

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Fear of Predators Drives Honey Bees Away from Good Food Sources

Science Daily 10/2/13

Most of us think of honey bees as having a bucolic, pastoral existence -- flying from flower to flower to collect the nectar they then turn into honey. But while they're capable of defending themselves with their painful stings, honey bees live in a world filled with danger in which predators seize them from the sky and wait to ambush them on flowers.

Such fear drives bees to avoid food sources closely associated with predators and, interestingly, makes colonies of bees less risk-tolerant than individual bees, according to a study published in this week's issue of the open-access journal PLOS ONE.

"This strategy of colonies collectively exhibiting significantly more caution than the riskier individual foragers may help honey bees exploit all of the available food sources, with some intrepid foragers visiting more dangerous food while the colony judiciously decides how to best allocate its foraging," says James Nieh, a professor of biology at UC San Diego.

Nieh worked with scientists at Yunnan Agricultural University in China to study the impact on foraging Asian honey bees of the monstrous-looking Asian Giant hornet, Vespa tropica, and a smaller hornet species known as Vespa velutina, which has invaded Europe and now poses a threat to European honey bees.

"The Asian Giant hornets are dangerous, heavily armored predators," says Ken Tan, the first author of the paper, who also works at the Chinese Academy of Science's Xishuangbanna Tropical Botanical Garden. "Bee colonies respond by forming balls of defending bees, encasing the hornet and, in some cases, cooking it to death with heat generated by the bees."

The researchers found that bees treated the bigger hornet species, which is four times more massive than the smaller species, as more dangerous. In a series of experiments, they presented bees with different combinations of safe and dangerous feeders -- depending on their association with the larger or smaller hornets -- containing varying concentrations of sucrose.

"Bees avoided the dangerous feeders and preferred feeders that provided sweeter nectar," says Nieh. "However, predators are clever and can focus on sweeter food, ones which bees prefer. So we also tested how bees would respond when sweeter food was also more dangerous. What we found was that the individual bees were more risk-tolerant. They avoided the giant hornet at the best food, but continued to visit the lower quality food with the smaller hornet."

Other scientists involved in the research were Zongwen Hu, Weiwen Chen, Zhengwei Wang and Yuchong Wang, all of the Eastern Bee Research Institute of Yunnan Agricultural University.