US bumblebee population plummets.

http://www.abc.net.au/news/stories/2011/01/04/3105930.htm?site=news


US bumblebee population plummets

Posted Tue Jan 4, 2011 10:25am AEDT


Weakened by inbreeding and disease, bumblebees have died off at an astonishing rate over the past 20 years, with US populations diving more than 90 per cent, a study said.

The findings are of concern because the bees play a crucial role in pollinating crops such as tomatoes, peppers and berries.

Similar declines have also been witnessed in Europe and Asia, said University of Illinois entomologist and study leader Sydney Cameron.

"The decline of bumblebees in the US is associated with two things we were able to study: the pathogen Nosema bombi and a decline in genetic diversity," he said.

"We are not saying Nosema is the cause; we don't know. It's just an association. There may be other causes."

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

The study examined eight species of North American bumblebees and found the "relative abundance of four species has dropped by more than 90 per cent, suggesting die-offs further supported by shrinking geographic ranges".

"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," the study said.

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.

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

The findings of the three-year study were published in the Proceedings of the National Academy of Sciences.

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