As Pollinators Decline, Plants Could Go It Alone
The yellow monkey flower, Mimulus guttatus, can quickly adapt to fewer pollinators in a few generations by changing its flowers to self-fertilize.
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A bee flies from plant to plant while feeding on a flowering Anigozanthus, also known as Kangaroo Paws, at a nursery in San Gabriel, California on March 25, 2013.
A sailing ship is visible on the Bodensee lake near Ueberlingen, Germany, on May 1, 2013. Flowers at the lakeside are visible in the front.
Visitors enjoy watching the Blue Nemophila flowers bloom during the Golden Week holidays, at Hitachinaka Kaihin Park on May 5, 2013 in Hitachinaka, Ibaraki, Japan.
A field of tulips at Magdeburg Börde in Schwaneberg, Germany, on May 3, 2013. Different species of the spring flowers are grown on more than 40 hectars.
A visitor looks at blooms at the Rhododendron Park in Bremen, Germany, on May 10, 2013. Nature is catching up after the unusually long winter. One effect is that rhododendrons normally bloom in succession, but now all of the flowers are blooming at once.
Villagers trim the tulip blossoms at a planting base in Qushui County, Lhasa City, capital of southwest China's Tibet Autonomous Region, May 9, 2013. The seed bulbs of tulip flowers were introduced into Lhasa from Yunnan Province.
Blossoms of a peach tree are visible in a garden in Eichwalde, Germany, on April 29, 2013.
A bee approaches cherry tree blossoms during a sunny spring day at a park in Brussels on April 14, 2013.
A woman meditates under a blooming cherry tree on the edge of the Potomace river in Washington D.C., on April 9, 2013.
A bee sits on a blooming Japanese cherry tree at the castle gardens in Schwetzingen, Germany, on April 15, 2013.
Different colored pansies are grown at a nursery near Kitzingen, Germany, 26 March 2013.
The sun shines through a blooming syringa bush in Berlin, Germany, on May 12, 2013.
The Guinness Book of World Records this spring certified this wisteria vine -- blooming at a Sierra Madre home on March 14, 2013, near Los Angeles -- as the world's largest blossoming plant. The wisteria vine is more than one acre in size and weighs 250 tons. It has more than 1.5 million blossoms every year with 40 blooms per square foot. The branches of this wisteria vine reach an 500 feet long. Horticultural experts have estimated the branches can grow 24 inches in 24 hours. The wisteria vine is a Chinese variety. It was planted in 1894 by William and Alice Brugman.
Blossoms of a Magnolia tree are visible on a sunny day with a clear blue sky in Dresden, Germany, 26 April 2013.
A bee seeks nectar on a ceanothus shrub at the Fullerton Arboretum in California.
White flowers on branches of the North American Cornus 'Florida', Flowering Dogwood.
The global decline in pollinators -- both wild and domesticated -- has scientists wondering if plants will adapt or die -- and the fate of a lot of our food hangs in the balance.
Some plant scientists now propose that many flowering plants could rapidly evolve strategies to avoid sinking with the pollinators, including self pollination and building tighter bonds with those pollinators that are still around.
"We consider two evolutionary scenarios that can occur in plant populations where cross-fertilization is made difficult" because of fewer pollinators, said researcher Pierre-Olivier Cheptou of UMR's Centre d'Ecologie Fonctionnelle et Evolutive in Montpeillier, France. Cheptou is a coauthor of a paper analyzing the two scenarios in the May 18 issue of the journal Trends In Plant Science.
Some plants, just because of their evolutionary history, have within their genes what amounts to a tool box of potential quick changes that can make, Cheptou explained. One of them is to decrease the distance between the fertile male and female sexual organs of the flower -- making it possible to self-fertilize. This is a good way to avoid immediate extinction, but it has serious drawbacks, since it amounts to extreme inbreeding which can magnify lethal genetic problems.
But many plants are unable to self-fertilize even when pollinated by hand. For these plants a more likely adaptation is to improve its attractiveness to pollinators by, for instance, increasing the size of the flower petals, or some other change that brings them crowding in.
"My plants did a little of both," said plant researcher Sarah Bodbyl of Michigan State University's W. K. Kellogg Biological Station. She has conducted experiments with an Oregon monkey flower, Mimulus guttatus, to see if they would tend, after a few generations, towards self-pollination with fewer pollinators around -- which they did. They also, perhaps coincidentally, got slightly larger flowers.
In some cases wooing pollinators better could help the pollinators too, Cheptou pointed out. If, for instance, more pollinators are coming because they get more nectar from certain plants, that would be good for the pollinators. But if all they get is a flashier flower to look at, it's more difficult to see any advantage for pollinators, he said.
And then, of course, there is a third evolutionary direction: extinction.
"If you lose your pollinator and can't adapt fast enough, you go extinct," said Bodbyl, adding that this is probably the most common scenario in the real world.
"For (some) plant populations adaptation to pollinator decline could not be possible at all because of the lack of genetic variance," agreed Cheptou. "We don't know what proportion of flowering plants could indeed adapt to the loss of pollinators." In other words, scientists are only beginning to understand how plants could adapt or die to the falling numbers of pollinators worldwide.