Bees latch on to similarly-sized nectarless flowers to unpick pollen – like keys fitting into locks, University of Stirling scientists have discovered.
Research, published in Ecology and Evolution, shows the right size of bee is needed to properly pollinate a flower. The insect fits tightly with the flower's anthers, to vibrate and unlock pollen sealed within.
Dr Mario Vallejo-Marin, from Stirling's Faculty of Natural Sciences, said: "We found that a pollinator's size, compared to the flower, significantly influences how much pollen is deposited."
Experts found more pollen grains are deposited when the pollinator's body is the same size or wider than the space between the flower's reproductive organs.
Dr Vallejo-Marin said: "Some plants, particularly those that are buzz-pollinated – a technique where bees hold onto the flower and vibrate to shake out the pollen – require a close physical interaction between their floral sexual organs and their visitors.
"The closer the bee fits to the flower, allowing it to touch both the male and female sexual organs, the more efficiently the insect can transfer pollen between plants."
Bees that are too small, relative to the size of the flower, transfer fewer pollen grains to other flowers and act 'pollen thieves', extracting the pollen they need without pollinating the flower.
Size does matter.
(Score: 2) by CoolHand on Thursday March 23 2017, @11:35AM (1 child)
Should this be turning me on? It sounds like some sort of weird interspecies menage-a-trois..
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(Score: 1, Funny) by Anonymous Coward on Thursday March 23 2017, @01:43PM
Sure. Bees know that you can just grab them by the pistil!
(Score: 2) by JoeMerchant on Thursday March 23 2017, @01:04PM
Birds knew it, bees knew it, now we have a study published about it.
🌻🌻 [google.com]
(Score: 4, Interesting) by Zinho on Thursday March 23 2017, @05:27PM
Research, published in Ecology and Evolution, shows the right size of bee is needed to properly pollinate a flower.
"The closer the bee fits to the flower, allowing it to touch both the male and female sexual organs, the more efficiently the insect can transfer pollen between plants."
Bees that are too small, relative to the size of the flower, transfer fewer pollen grains to other flowers and act [as] 'pollen thieves', extracting the pollen they need without pollinating the flower.
It seems that this article is very flower-centric; I'm guessing it was written by a botanist rather than an entomologist. Why should the bee care how much of the pollen gets transferred back to the flower? I would think that the bee's preference would be to maximize pollen carried back to the hive. The evolutionary aspect of this would perhaps involve flowers whose blossom size/reproductive organ geometry are selected for by being successfully pollinated by the common bee species in the region. Producing tons of excess pollen to attract more bees is probably a tradeoff between energy spent and reproductive success on the part of the plant. Anyone have a bead on how much effort it takes for a plant to produce more pollen vs less?
Regardless, I don't see a need to accuse smaller bee species of theft just because the blossom isn't optimized for them. From the article:
Dr Vallejo-Marin said: "Some plants, particularly those that are buzz-pollinated – a technique where bees hold onto the flower and vibrate to shake out the pollen – require a close physical interaction between their floral sexual organs and their visitors.
This suggests that the properly-sized bees are able to extract more pollen than their too-small counterparts by using a more effective (if less efficient) method of extraction. The real question for the the botanists is, "does this harm the plant?" Well, no. Again, from the article:
Dr Vallejo-Marin added: "Surprisingly, visits by smaller bees were associated with more seeds being produced, indicating that more pollen does not necessarily create more seeds. Seed production may also depend on the quality of the pollen and different kinds of pollen grains competing to germinate.
Who, then, are the thieves here? If the smaller bees are being more effective at germination than their wrong-pollen-dumping larger cousins then they should be welcome at the buffet. Presumably, seed production is the end goal here, not simply application of random pollen to the female flower organs.
For reference, the same author published another study a while back basically saying the same thing, [phys.org] without the moderating comment about increased seed production after visits from smaller bees. I can only hope that the potato/tomato/pepper farmers in Mexico haven't been taking steps to eliminate the "invasive" European honey bees for the last year and a half based on the previous publication; they'd have only been hurting themselves in the process.
Practical advice based on this paper would be to encourage more diversity in crops, perhaps re-planting those extra seeds provided by the small-bee pollination. From an evolutionary perspective the poorly-pollinated plants are simply not as fit for the new environment. Unless conservation efforts are in order to preserve a critical species or prevent crop failures this talk of pollen theft is simply academic hand-wringing or alarmism in pursuit of extended funding.
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