The Latest Buzz on Bumblebees - Evolution News & Views

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The Latest Buzz on Bumblebees


When it comes to finding food, bumblebees don't bumble very often. They are well equipped to detect the best flowers to pollinate. Recent research shows two more unexpected ways they avoid costly errors.

That buzzing of bees that we hear sounds almost electric. Even though it is produced by rapidly flapping wings, scientists at the University of Bristol found that electrical cues indeed play a measurable role in bee foraging. Publishing in Science, they announced an intriguing discovery:

We report a formerly unappreciated sensory modality in bumblebees (Bombus terrestris), detection of floral electric fields. These fields act as floral cues, which are affected by the visit of naturally charged bees. Like visual cues, floral electric fields exhibit variations in pattern and structure, which can be discriminated by bumblebees. We also show that such electric field information contributes to the complex array of floral cues that together improve a pollinator's memory of floral rewards. Because floral electric fields can change within seconds, this sensory modality may facilitate rapid and dynamic communication between flowers and their pollinators. (Emphasis added.)
The paper reads like a classic example of good controlled experiment: hypothesis, experimental design, control. First, the four scientists had to measure electric fields on natural bees, natural flowers, and in the ambient air, to establish a baseline. Did you know most insect pollinators are positively charged, and most flowers are negatively charged? That's not all. By dusting six different species of flowers with colored electrostatic powder, they found distinctive species-specific patterns of electric fields on the petals, stamens and ovaries, almost like signals telling the bees, "It's right in here!"

To test the hypothesis that floral electric fields function as cues, they built an apparatus with artificially charged structures ("E-flowers"). They trained 51 bumblebees "to fly into a Faraday pail that contained a sucrose reward." With surprising accuracy, the bees learned to fly to the charged E-flowers instead of the ones in the electrical ground state, even thought there were identical in all other respects. But when the charged flowers were discharged, the bees could no longer discriminate between the sucrose-loaded ones and the empty ones. The researchers also found that the bees could learn to associate a specific pattern of electric field with the reward.

This showed that the bumblebees were able to detect electric field patterns and use that information to find the reward, but was it the only cue? To study the effect of multi-modal cues, the team combined the electric cue with color cues: one color tasted good, another bad. It took most bees 35 visits to achieve 80% success. When the electric field was added, most found them much faster, in just 24 visits. This showed that a combination of cues improves foraging efficiency. In conclusion, they said:

Our results show that electric field constitutes a floral cue. Contributing to a varied floral display aimed at pollinator senses, electric fields act to improve both speed and accuracy with which bees learn and discriminate rewarding resources. As such, electric field sensing constitutes a potentially important sensory modality, which should be considered alongside vision and olfaction. The ubiquity of electric fields in nature and their integration into the bees' sensory ecology suggest that E-fields play a thus far unappreciated role in plant-insect interactions. The present study raises the possibility of reciprocal information transfer between plants and pollinators at time scales of milliseconds to seconds, much faster than previously described alterations in floral scent, color, or humidity. The remarkably accurate discrimination and learning of color patterns by bees was revealed by both laboratory and field training experiments. Similarly, the present laboratory study reveals that floral electric fields occur in patterns and that they can be perceived. Hence, our study provides a framework for exploring the function and adaptive value of the perception of weak electric fields by bees in nature.
Meanwhile researchers at Queen Mary University of London have found that bumblebees employ a simple form of logic. They can learn from watching their neighbors' hit rates to decide what flowers to visit. In experiments with laboratory "flight arenas," bees "actively avoided" flowers that other bees found distasteful.

The researchers claimed it's simply logical for a bee, or any other animal, to learn from others:

Despite their tiny brains, bees are smart enough to pick out the most attractive flowers by watching other bees and learning from their behaviour. By using simple logic, they see which coloured flowers are the most popular, and conclude that those of the same colour must also contain lots of energy-rich nectar.

"Learning where to find nectar by watching others seems fantastically complex for a tiny bee, but it's something that almost any animal could do, in the right circumstances," says Dr Elli Leadbeater from ZSL's Institute for Zoology.....

This suggests that other species, not just bees, may also use this logical process when learning from others.

Try formulating that as a syllogism. Major premise: My neighbors will devote energy to the best food sources. Minor premise: That colored flower is popular. Conclusion: The popular flowers must have the best food sources.

This kind of deductive logic requires the ability to form associations. It also presupposes a good memory. That's a lot to pack into a tiny bee brain.

Nor is that all. Electric field detectors, olfactory senses, and some 6,000 facets of their compound eyes all have to send information to the brain, where the information must be integrated with memory to make reliable decisions. Bumblebees are pretty complex creatures.

Neither article mentions evolution, confirming again that evolutionary theory is often superfluous to scientific research. Critics of ID might retort, "Well, that doesn't mean this was intelligent design research!" Doesn't it?

True, there is also no mention of specified complexity, irreducible complexity, or the design filter. There is no reference to major ID books. But Dembski, Meyer and other leading lights of the intelligent-design community have said that one of their goals was to formally describe the way that human beings reach design conclusions from the evidence, according to rigorous mathematical principles. One doesn't need to use explicit ID language to do that. Design detection is largely an intuitive logic we all use every day; ID helps make it robust.

Scientists, especially, are trained to figure out how things work. These articles are in the "how it works" category, not the "where did it come from" category. As Paul Nelson says in the upcoming film from Illustra Media on bird flight, "It if works, it's not by accident."

We see bumblebees with highly specialized, multi-modal equipment for finding nectar. Regardless of the researchers' personal beliefs about the origins of complex life, they were focused on complex functions that work. If something works, and if the research has no need of unguided processes to explain it, then yes: it's de facto intelligent-design research.

Image credit: John W. Coke/Flickr.