September 8, 2010

The Mysterious Collapse of the American Honeybee

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Four years ago, a commercial beekeeper, who had trucked thousands of his honeybee colonies to winter in Florida, discovered that all the bees had disappeared. There were no skeletons, so to speak. The bees were just gone.

This occurrence, known as colony collapse disorder, was a natural one because, in order to survive through cold weather, colonies need to store a certain amount of nectar and pollen.

“Some proportion of colonies aren’t able to do that, so they die off,” explained Prof. Bryan Danforth, professor, entomology. Colony collapse disorder only became the subject of widespread concern four years ago because instead of the steady 20 to 30 percent loss in colonies every year, beekeepers began reporting a 40 to 50 percent loss.

Many explanations were given: pathogens, viruses, pesticides (which kill insects, including bees), being fed high fructose corn syrup (instead of honey and pollen), being transported – literally – across the country (which induces stress and facilitates the transmission of diseases), and consequently being treated with antibiotics for diseases.

No one explanation fully explains the sudden rise in colony collapse disorder, and Danforth’s opinion is that the answer is a combination of factors.

He emphasized, though, that the concern over Apis mellifera, the Western honeybee, is an economic, not environmental, one. Honeybees are not native to North America.

“If the honeybee goes extinct in North America, frankly, I don’t think that’s a sign of some environmental catastrophe,” Danforth said.

Honeybees are cultivated in the U.S. to pollinate the nation’s vegetables, fruits, and quite profitably, almonds. Half of the honeybees in the U.S. (1.25 million) are loaded onto trucks and driven to California every February to pollinate almonds.

Although Apis mellifera is only one of 20,000 species of bees in the world, it is the celebrity and moneymaker of the bee kingdom, highly valued for its ability as a “social insect,” an insect raised to be used commercially and to communicate with each other about crop locations. In contrast, most native bees are solitary, difficult to commercialize, and largely unprofitable.

While colony collapse disorder has intensified the research on honeybees, it has also attracted attention to the 4,000 species native to North America, which may turn out to be the American agriculture industry’s “Plan B” for pollination.

“So much of the focus on bees and on bees as pollinators has been on honeybees,” Danforth said. Yet, the contribution of native bees versus the honeybee to pollination is little studied and largely unknown despite native bees being widely distributed and effective pollinators.

Danforth intends to help promote the study of native bees through his lab’s participation in the National Science Foundation-funded bee database, which is synthesizing the data from 10 U.S. institutions. The university’s collection began in the 1870s with John Henry Comstock, and has since expanded to 250,000 specimens.

The bee database project will pool the data and make it available through the Discover Life website. The website, accessible by researchers as well as the general public, gives information and a distribution map for each species.

“Given that the honeybees are in trouble and given that we need to know more about what the native bees are doing,” we need to be tracking bee distributions over time, Danforth said.

Danforth, a native New Yorker, is further contributing to knowledge of native bees by studying their role in the pollination of New York apple orchards. He and Mia Park grad have been conducting a long-term survey of orchards in the Finger Lakes area.

They found that 40 to 50 percent of apple growers no longer pay to be supplied with honeybee colonies. This is especially true for smaller orchards.

“You can rely on native bees because you probably have a lot of relatively natural habitat surrounding your orchards,” Danforth explained.

For orchard larger than 100 acres, there would not be enough native bees to sustain the needs of the crop.

In the 20 orchards they visited, Danforth and Park identified 80 species of native bees, double their intial expectation. One genus, Andrena, is a particularly abundant pollinator, accounting for half of the specimens collected.  They outnumber honeybees in collections.

Park identified several characteristics that make species of Andrena more effective pollinators than honeybees. The physical and behavioral biology of these native bees better equips them to hold onto pollen and transfer it, and Andrena bees concentrate their efforts on pollen, whereas honeybees collect both pollen and nectar. Within apple orchards, which require cross-pollination, Andrena bees have also been observed to be more widely dispersed.

Andrena bees seem to have an affinity for apples, and indeed, orchards provide them with a stable habitat. They are ground-nesting bees, and apple growers do not till the land, which would disturb Andrena nests, or apply a great deal of pesticides.

Perhaps most importantly, apples are an annual crop, and the two to three weeks every spring when native bees are active coincides with the apple blooming season. Honeybees, Park pointed out, live for the entire growing season and consequently, must be generalists to maintain a steady food source.

For apple crops in New York State alone, Danforth’s lab found that native bees are just as, if not more, important in pollination.

“Ten years ago.  If someone wanted to estimate the economic value of the honeybee, they’d add up the economic value of pollination. That means they’re assuming the honeybee is pollinating everything. That’s not a fair assumption at all,” Danforth said.

Original Author: Jing Jin