US sees massive drop in bumble bees: study

Yahoo News 3 Jan 11;

WASHINGTON (AFP) – Weakened by inbreeding and disease, bumble bees have died off at an astonishing rate over the past 20 years, with some US populations diving more than 90 percent, according to a new study.

The findings are of concern because bees play a crucial role in pollinating crops such as tomatoes, peppers and berries, said the findings of a three-year study published in the Proceedings of the National Academy of Sciences (PNAS).

Similar declines have also been seen in Europe and Asia, said Sydney Cameron, of the Department of Entomology and Institute for Genomic Biology at the University of Illinois, the main author of the study.

"The decline of bumble bees in the US is associated with two things we were able to study: the pathogen Nosema bombi and a decline in genetic diversity. But we are not saying Nosema is the cause. We don't know," said Cameron.

"It's just an association. There may be other causes."

He added that the decline is "huge and recent," having taken place in the last two decades.

Nosema bombi is a bee pathogen that has also afflicted European bumble bees.

Researchers examined eight species of North American bumble bees and found that the "relative abundance of four species has dropped by more than 90 percent, suggesting die-offs further supported by shrinking geographic ranges," said the study.

"Compared with species of relatively stable population sizes, the dwindling bee species had low genetic diversity, potentially rendering them prone to pathogens and environmental pressures."

Their cousins, the honey bees, have also experienced catastrophic die-offs since 2006 in a phenomenon known as "colony collapse disorder," though the causes have yet to be fully determined.

Bumble bees also make honey, but it is used to feed the colony, not farmed for human consumption.

They are however raised in Europe for pollinating greenhouse vegetables in a multi-billion-dollar industry that has more recently taken off in Japan and Israel and is being developed in Mexico and China, Cameron said.

"We need to start to develop other bees for pollination beside honey bees, because they are suffering enormously," he added.

There are around 250 species of bumble bee, including 50 in the United States alone.

Researchers Find "Alarming" Decline In Bumblebees
Maggie Fox PlanetArk 4 Jan 11;

Four previously abundant species of bumblebee are close to disappearing in the United States, researchers reported Monday in a study confirming that the agriculturally important bees are being affected worldwide.

They documented a 96 percent decline in the numbers of the four species, and said their range had shrunk by as much as 87 percent. As with honeybees, a pathogen is partly involved, but the researchers also found evidence of inbreeding caused by habitat loss.

"We provide incontrovertible evidence that multiple Bombus species have experienced sharp population declines at the national level," the researchers reported in the Proceedings of the National Academy of Sciences, calling the findings "alarming."

"These are one of the most important pollinators of native plants," Sydney Cameron of the University of Illinois, Urbana, who led the study, said in a telephone interview.

In recent years, experts have documented a disappearance of bees in what is widely called colony collapse disorder, blamed on many factors including parasites, fungi, stress, pesticides and viruses. But most studies have focused on honeybees.

Bumblebees are also important pollinators, Cameron said, but are far less studied. Bumblebees pollinate tomatoes, blueberries and cranberries, she noted.

"The 50 species (of bumblebees) in the United States are traditionally associated with prairies and with high alpine vegetations," she added.

"Just as important -- they land on a flower and they have this behavior called buzz pollination that enables them to cause pollen to fly off the flower."

POLLINATING TOMATOES

This is the way to pollinate tomatoes, Cameron said -- although smaller bees can accomplish the same effect if enough cluster on a single flower.

Several reports have documented the disappearance of bumblebees in Europe and Asia, but no one had done a large national study in the Americas.

Cameron's team did a three-year study of 382 sites in 40 states and also looked at more than 73,000 museum records.

"We show that the relative abundance of four species have declined by up to 96 percent and that their surveyed geographic ranges have contracted by 23 percent to 87 percent," they wrote.

While no crops are in immediate danger, the results show that experts need to pay attention, Cameron said. Pollinators such as bees and bats often have specific tongue lengths and pollination behaviors that have evolved along with the species of plants they pollinate.

Bumblebees can fly in colder weather than other species, and are key to pollinating native species in the tundra and at high elevations, Cameron said.

Genetic tests show that the four affected bumblebee species are inbred and other tests implicate a parasite called Nosema bombi, Cameron said.

"This is a wake-up call that bumblebee species are declining not only in Europe, not only in Asia, but also in North America," she said.

(Editing by Vicki Allen)

Four Bumblebee Species on the Decline in North America
Wynne Parry LiveScience.com Yahoo News 3 Jan 11;

The populations of four species of North American bumblebee have declined, a new study has confirmed. The study also found that fungal infections are more likely to plague these bees than other, more stable bumblebee species.

Although perhaps not as dramatic as the sudden disappearance of honeybees, a phenomenon dubbed colony collapse disorder, reports of vanishing bumble bees have appeared in recent years in North America and Europe.

Until now, however, the North American reports were isolated and small-scale, according to Jeffrey Lozier, a study researcher and postdoctoral researcher at the University of Illinois.

"What we wanted to do is say 'If you look at the entire country, do these patterns hold up?'" Lozier said. "We picked these target species because they sort of were canaries in the coal mine."

What they found added credence to worries of coast-to-coast declines in some - but not all - bumble bees and more evidence of trouble for pollinators that fertilize both wild plants and crops. The cause remains unclear and may be complex.

"We need to keep a general view that pollinators seem to be declining, but each bumblebee species may be responding to different pressures that are causing declines," said James Strange, a study author and a research entomologist with the U.S. Department of Agriculture. "Not all the bees are disappearing. It turns out there may be winners and there may be losers."

Bee collecting

Like honeybees, bumblebees are employed to pollinate agricultural crops. Though they are less numerous, their high-frequency buzz gives them an advantage, as the sound waves free more pollen than a honeybee's buzz, and their large size allows them to continue working in colder temperatures, according to Lozier.

The study focused on the western bumblebee, the American bumblebee, the rusty-patched bumblebee, and the yellowbanded bumblebee. Collectively, their ranges span the continental United States, while the researchers trapped bumblebees at 382 locations across the country. They also collected data on four species of bumblebee believed to be stable, and their results indicated that these were indeed doing fine.

To get a sense of how the abundance and distribution of the bees may have changed, the researchers looked at bumblebees preserved in museum collections from 1900 to 1999, compiling a database of more than 73,000 historical specimens.

Their findings revealed that among the bees collected in the field from 2007 through 2009, the four target species made up much smaller portions of the total catches than they had historically. These changes in relative abundance began to appear within the last 20 to 30 years, according to the research published Jan. 3 (Monday) in the journal the Proceedings of the National Academy of Sciences.

Based on this data, the researchers estimated that the four target species had also seen their ranges decline. For example, the researchers collected western bumblebees in the Rocky Mountains and the intermountain west (between the Rockies and the Pacific coast), but it was largely absent from the western portion of its historical range, closer to the Pacific coast.

The survey found only 22 rusty-patched bumblebees and 31 yellow-banded bumblebees.

Cause still unknown

The researchers also looked for infections by a fungus - Nosema bombi - and at the level of genetic diversity among the eight bumblebee species. They found that 37 percent of the western bumblebees they collected carried the fungus, and 15 percent carried it among the American bumblebee, significantly higher infection rates than those seen among the four stable species. Although there was evidence of higher infection rates among the other two target species, too few were collected to provide any definitive results.

While these findings indicate an association between the fungus and declining populations, they don't necessarily show that the fungus is driving the declines, Lozier said.

For the American and western bumblebee, researchers found that populations also had less genetic diversity than stable species. (Once again, too few samples were collected from other two species.) This is significant because genetic diversity enables a population to respond to changing environments or novel threats like disease, according to Lozier.

"The amazing thing we did find is gene flow appears very high," Lozier said. For example, American bumblebees caught in Texas were genetically indistinguishable from those from South Dakota, suggesting the bees are reproducing (and spreading genes) across wide swaths of the United States.

"If gene flow is really this high, it could prove a potential mechanism for the spread of the pathogen," he said.

The puzzle of pollinator declines

The origin of the fungus and how it spread isn't completely clear, but there are theories. It has been theorized that, after decimating commercial bumblebee facilities in California, N. bombi escaped and became responsible for declines among wild populations in the Pacific Northwest, according to these researchers.

The elevated N. bombi infections among struggling bumblebees, and the possibility that the fungus was introduced from Europe, calls to mind reports of other introduced fungal pathogens decimating species - like the chytrid fungus killing amphibians on multiple continents and Geomyces destructans, which is wiping out some North American bats, they write.

Two papers published in December in the journal PLoS ONE explored the plethora of infections faced by honeybees. One paper found that a certain type of virus implicated in colony collapse disorder may be transmitted by pollen and can infect other pollinators such as bumblebees and wasps. Another study linked a viral-fungal tag team to the disorder. The researchers of those studies found that infection becomes more lethal when the virus and fungus infected the same bee together.