Bee Colony Collapse Not Due to Inbreeding

Friday, 28 September 2012

Anna Salleh ABC

The mysterious and widespread collapse of bee colonies in many parts of the world is not due to a lack of genetic diversity, a new study has found.

The study by Brock Harpur, of York University in Canada, and colleagues, is reported in a recent issue of Molecular Ecology.

"The relationship between genetic diversity and honey bee declines is tenuous given that managed bees have more genetic diversity than their progenitors and many viable domesticated animals," write the researchers.

In recent years, bee colonies in Europe and North America have been suffering widespread collapse.

Just as the process of domestication with other animals often brings about a decline in genetic diversity, some scientists believe this has occurred in managed bees and is the cause of colony collapse.

"The honey bee, Apis mellifera, has been managed by humans for centuries for both honey and wax production and crop pollination," write Harpur and colleagues.

"Human management and selective breeding are believed to have caused reductions in genetic diversity in honey bee populations, thereby contributing to the global declines threatening this ecologically and economically important insect."

But in their genetic study, Harpur and colleagues found evidence against this.

"We found that managed honey bees actually have higher levels of genetic diversity compared with their progenitors in East and West Europe," they write.

Professor Ben Oldroyd of the University of Sydney welcomes the latest study on the genetic diversity of managed bees.

"[Harpur and colleagues] were using a new genetic marker ... So they got a really good handle on it," says Oldroyd, who studies the behavioural, evolutionary and population genetics of bees.

Oldroyd has also found similar genetic diversity of managed bees in Australia, which to date does not have colony collapse disorder.

He says diversity in managed bees can be explained by the fact that beekeepers' regularly import new queen bees from many parts of the world, and then these queens mate with feral bees.

This is quite different from what happens in the domestication of many other animals.

"In cattle there's this big thing about staying within the breed but beekeepers don't do that. Bees are a mongrel lot, like humans," says Oldroyd.

Colony collapse - something new?

Oldroyd says in the past he has been a skeptic of whether the collapse of colonies is a new development in the history of bees.

"There's been occurrences throughout history, going back as far as the 10th century where there's been massive die offs of bees," he says.

"There was a big die off in 1910 in England when just about every colony died."

But, Oldroyd says his view is shifting as time goes on, given the world-wide scale of colony collapse, and number of colonies involved.

He says there are many other theories for the problem ranging from the effect of mobile phone towers (popular in India) to the stress of bees from overwork in industrial-scale beekeeping.

"The typical pattern in the United States is the bees are overwintered in Florida, driven to California for almond pollination and then they're driven up to the north west to New York for pollinating apples and then maybe they'll even get a honey crop in Canada," says Oldroyd.

"They work them hard. Particularly the queens get a hard time because they have got to be laying one to two thousand eggs a day for most of the year instead of for a few months."

But, he says the most likely cause of colony collapse disorder is pesticides, including, neonicotinoids that disorient bees so they can't get back to their nest.

"If there was any one thing that was supposed to be the cause of colony collapse I suppose that's the most likely one," says Oldroyd. "I think the evidence is mounting on that."

Source: ABC Science