Scientists at the University of Illinois say bees with declining populations show lower genetic diversity than species with healthy numbers, and are more likely to be infected with Nosema bombi, a parasite known to afflict some species of bumble bees in Europe, a university release said Monday.
"We have 50 species of bumble bees in North America. We've studied eight of them and four of these are significantly in trouble," said UI entomology professor Sydney Cameron, who led the study. "They could potentially recover; some of them might. But we only studied eight. This could be the tip of the iceberg."
The study found the relative abundance of four of the analyzed species has declined by as much as 96 percent and their surveyed geographic ranges have shrunk by 23 percent to 87 percent.
Some of the contractions have occurred in the last two decades, researchers say.
Climate change appears to play a role in the declines in some bumble bee species in Europe, Cameron said, while habitat loss may contribute to the loss of some specialist species, and low genetic diversity and high infection rates of the parasite must be considered suspects in the declines.
"Whether it's one of these or all of the above, we need to be aware of these declines," Cameron said. "It may be that the role that these four species play in pollinating plants could be taken up by other species of bumble bees.
"But if additional species begin to fall out due to things we're not aware of, we could be in trouble."