Bumblebee species 'in trouble': U.S. study

Four of the 50 species of bumblebees found in the U.S. are "significantly in trouble," University of Illinois entomology professor Sydney Cameron said Tuesday.

Cameron,lead author ofthe first in-depth national study of wild bees in the U.S., said the analysis only covered eight species, so "this could be the tip of the iceberg."

The finding echoes similar ones in other reports that documented huge declines in honeybee populations.

Using historical records from the late 1800s, Cameron and her colleagues found the relative abundance the proportion of the studied speciesout of all bumblebees of the four species decreased by up to 96 per cent since that period, and their geographic range contracted by between 23 and 87 per cent.

The study said that the declining populations had significantly higher infection levels of the pathogen Nosema bombi than unaffected populations. Separate research has shown that the parasite can renderbumblebees helpless and unable to function, and eventually kill them.

The infected populations also had lower genetic diversity.

"Higher pathogen prevalence and reduced genetic diversity are, thus, realistic predictors of these alarming patterns of decline in North America, although cause and effect remain uncertain," the abstract of the study said.

Research last year on colony-collapse disorder, whichled to themass deaths of honeybee colonies,suggests the collapse mighthave beencaused by a combination of viruses and the fungi Nosema apis and Nosema ceranae.

Cameron said there is no proven cause of the bumblebee declines, butclimate change has contributed to European losses andhabitat loss may affect certain specialized species.

The Committee on the Status of Endangered Wildlife in Canada last May said the rusty-patched bumblebee should be listed as endangered. Its rapid declineis a mystery, but pesticides, disease and a loss of habitat could becontributing factors.

The three-year U.S. study compared more than 73,000 museum records with recent U.S. national surveys of more than 16,000 specimens from about 400 sites.

The report was published in the Proceedings of the National Academy of Sciences.