[Pollinator] Flowers Evolve to Suit Birds and Bats

[Ladadams at aol.com]

Flowers Evolve to Suit Birds and Bats

By Heather Whipps
Special to LiveScience
posted: 20 April 2007
11:37 am ET

The varying shapes of flowers found in tropical forests, from broadly 
blooming to delicately narrow, may have to do with what has stuck its nose in there 
to pollinate in past evolutionary eras.  
 Different species of birds and bats may have encouraged flowers to evolve to 
fit the shape of their snouts or beaks, new findings suggest.  
 Flowers seem to respond to whatever is available and doing the best job of 
spreading pollen, said study leader Nathan Muchhala, a University of Miami 
biologist. Birds and bats have also changed their body shapes over time to adapt 
to available food sources and flower and plant shapes, but flowers have done so 
more aggressively, he said.  
 "Basically, the flowers are making an evolutionary decision," he told 
LiveScience. "Organisms can specialize in something (like having wide or narrow 
openings), but they have to make the tradeoff to be good at one or the other."  
 The findings are detailed in this month's issue of the American Naturalist. 
 
 If the snout fits  
 Biologists have long observed that pollinators such as birds and bats seem 
to favor different shapes and species of flowers. However, there has never been 
evidence to support the idea that flower diversity is a direct result of the 
need to "choose" one shape over another depending on the pollinator.  
 To test this, Muchhala and his team captured (and later released) a species 
of nectar bat and hummingbird in the rainforests of Ecuador and brought them 
together with a variety of artificial flowers—filled with honey water—like the 
ones found locally.  
 Flower-pollinator fit was crucial in successful pollination, the results 
showed.  
 The hummingbirds, with their long and thin beaks, were better guided by 
flowers with similarly narrow shapes. On the other hand, the much larger bats made 
better contact with flowers that had wider openings.  
 Lots of pollen dropped to the ground and was wasted by each animal when the 
reverse was tested, Muchhala said, and also forced the animals to fly in at odd
—and probably uncomfortable—angles.  
 It has probably been a bit of a give and take relationship over the years, 
Muchhala said, with the flowers doing most of the evolutionary work.  
 "There is definitely some degree of co-evolution (simultaneously adapting 
together), which you can see just in the fact that flower visiting bats and 
birds have longer snouts than other bats and birds," he said. "However, flowers 
seem to respond faster."  
 There isn't just one flower species per bat or bird, Muchhala clarified.  
 "This is a common misconception—that is, that each flower has its bat/bird 
specialist, and they are tightly interdependent," he said. "The one exception 
is a bat with an extremely long tongue (140 percent of body length!) that I 
recently discovered in Ecuador—a flower with a matching tube length is 
exclusively specialized to this bat," he said.  
     •      How Flowers Know Spring Has Sprung

     •      Human Affection Altered Evolution of Flowers

     •      The Bizarre Sex Life of an Orchid

Close up of a hummingbird feeding at the artificial flower. Credit: Nathan 
Muchhala, Department of Biology, University of Miami, Florida

> Click to View


Nathan Muchhala working on the artificial flower with a bat hovering by his 
leg in mid-air. Credit: Nathan Muchhala. Department of Biology, University of 
Miami, Florida

> Click to View





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