[Pollinator] Unraveling the Pollinating Secrets of a Bee's Buzz

[Ladadams at aol.com]

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Matter - New Your TImes
Unraveling the Pollinating Secrets of a Bee’s Buzz
 


 
 
 
 
 

Mario Vallejo-Marín/University of  Stirling

 

Anne Leonard/University of Nevada, Reno;  Stephen Buchmann, Daniel 
Papaj/University of  Arizona





 
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By CARL  ZIMMER
Published: July 11, 2013 
 


     
Now is the time of year when bees buzz from flower to  flower. And for many 
plants, the very survival of their species depends on that  buzz. The 
flowers and the insects are joined together in a partnership of sound. 
 
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Nikola Solic/Reuters
Bumblebees use their jaws and wings to shake pollen out of  flowers for 
food in a process called buzz pollination. 
 
 
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Earl Wilson/The New York Times
Carl Zimmer 

 
Bumblebees and other insects use buzzing to shake  pollen out of flowers 
for food — and they fertilize flowers along the way.  Scientists are exploring 
this acoustic feat to figure out how it has evolved,  and how it helps 
sustain our own food supply.  
Flowering plants typically reproduce by delivering  pollen to each other to 
fertilize seeds. Some flowers, like corn and ragweed,  cast their pollen to 
the wind. Others depend on animals like bees, bats or birds  to do the job. 
 
In many cases, these flowers lure an animal with the  reward of nectar. As 
the pollinator sips the plant’s sugary liquid, it gets  covered in pollen. 
It then travels to another flower in search of nectar and  delivers the 
grains.  
But 20,000 plant species — including familiar ones  like tomatoes, potatoes 
and cranberries — strike a different deal. They offer  pollen itself as 
food. These flowers don’t simply put the protein-rich pollen  out for any 
animal to eat, however. They keep it tucked deep inside special  tubes.  
Only bumblebees and certain other insects can get this  pollen out. In 
every case, the method is the same: the pollinator grabs the tube  with its jaws 
and starts vibrating hundreds of times a second.  
“It has to hold on, because the vibrations are so  strong that otherwise it 
could come flying off the flower,” says Mario  Vallejo-Marín of the 
University of Stirling in Scotland, who recently  co-authored a _review_ 
(http://www.sciencedirect.com/science/article/pii/S1369526613000630?via=ihub)   of this
 behavior in the journal Current Opinion in Plant Biology.  
The animals produce a peculiar buzz with this  technique. “It sounds like a 
bee is giving you a raspberry,” said Stephen  Buchmann of the University of 
Arizona. In fact, they’re creating resonating  vibrations to loosen the 
pollen grains inside the tubes. “The bees are turning  themselves into living 
tuning forks,” said Dr. Buchmann.  
The bees cause the pollen grains to bounce up and down  in the tube and 
then gain so much energy they blast out in a cloud that coats  the bee. As it 
flies off, the insect gathers the grains out of its fur and tucks  most of 
them in wet clumps on its legs. It can later feed the clumps to larvae  back 
at its hive.  
“Fortunately, they’re a little bit messy,” said Dr.  Buchmann. When the 
bee visits another flower for a buzz, the extra pollen still  on its body can 
fertilize the plant.  
“It seems so unlikely — it would never work if you  were designing a plant,
” said Anne Leonard, an ecologist at the University of  Nevada at Reno. “
But it’s evolved many times.”  
Dr. Leonard belongs to a small coterie of scientists  who are trying to 
understand the evolution of so-called buzz pollination.  
The transformation probably starts when a plant  species shifts to using 
pollen as a lure instead of nectar. If the flowers  simply put out the pollen 
like cookies on a table, an assortment of insects may  steal it and never 
pass on any grains to another flower. Growing a tube to store  away the pollen 
gives flowers control over who can eat it — and the power to  dust visitors 
with it, as well.  
Once flowers hide away their pollen this way, natural  selection favors 
bees that can give the flowers a harder shake. The harder the  bees shake, Dr. 
Vallejo-Marín and his colleagues _have  found_ 
(http://link.springer.com/article/10.1007/s00442-012-2535-1) , the more food they can bring home. Bees 
experience forces 30 times  greater than gravity as they buzz for pollen — 
near the limit of human  endurance.  
That can be too much of a good thing for the flower,  though. If a bee 
shakes out a plant’s entire pollen supply, it carries the  flower’s whole 
reproductive future with it. “The risk of a failure can be very  high,” said Dr. 
Vallejo-Marín.  
Dr. Vallejo-Marín suspects that this risk of failure  drove the continued 
evolution of the flowers. The shape of the tubes changed so  that even harder 
buzzing could only free a fraction of the pollen, meaning a  single greedy 
bee couldn’t exhaust a plant’s supply. Instead, the flowers have  enough 
pollen to spread over several bees, raising the odds that their genes  will 
get into the next generation.  
There’s a lot more that scientists have left to learn  about buzz 
pollination. Are flowers tuned to particular species of bees, for  example? Why can 
bumblebees buzz pollinate, but honeybees can’t?  
Understanding buzz pollination is not just interesting  in its own right, 
but a matter of pressing importance. Bumblebees and other buzz  pollinators 
are suffering _worrying_ (http://www.pnas.org/content/108/2/662)  _declines_ 
(http://www.sciencemag.org/content/339/6127/1611.full) ,  probably due to a 
combination of threats like diseases, pesticides and  destruction of their 
habitat. Their decline threatens the many wild plants that  have evolved to 
depend on their buzz. And a lot of food on our dining room table  depends on 
the buzz as well.  
“We could live just on wind-pollinated plants like  wheat and barley and 
millet,” said Dr. Buchmann, wearily listing each food, “but  it would be a 
pretty bland, nasty diet.”  
 
Carl Zimmer’s “Matter” column appears on Thursdays. Follow him on Twitter: 
_ at carlzimmer_ (https://twitter.com/carlzimmer) .







 
 
 
 
 
 
 
Laurie Davies  Adams
Executive Director
Pollinator Partnership
423 Washington St.  5th Fl.
San Francisco, CA 94111
T: 415.362.1137
F: 415.362.0176

Follow up on _Twitter_ (http://twitter.com/#!/Pollinators)  and _Facebook_ 
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