It seems bees have their own special brand of workplace bullying, with queens able to effectively control the fertility of their workers.

But how can it happen?

Kiwi scientists have just discovered that an ancient cell-signalling pathway called "Notch" has been cleverly used by queen bees control their workers' reproduction.

It has long been known that worker bees have a very limited ability to reproduce in a hive with a queen and brood present, but in their absence, a third of them will activate their ovaries and lay eggs that hatch into fertile male drones.


It is queen pheromone that represses worker bee fertility, but how it achieves this has remained unclear.

Now, genetics researchers at Otago University have identified that the pathway Notch, which plays a major role in regulating embryonic development in all animals, has been co-opted to also constrain reproduction in worker bees.

In research just published in the journal Nature Communications, authors Professor Peter Dearden, Dr Elizabeth Duncan and Otto Hyink have demonstrated that chemically inhibiting Notch signalling can overcome the effect of queen mandibular pheromone (QMP) and promote ovary activity in adult worker bees.

Professor Dearden said they were surprised to find that Notch signalling acted on the earliest stages of egg development in the ovary, perhaps even on the stem cells that make the ovary, and that in the absence of QMP, the Notch receptor in a key region of worker bee ovaries became degraded.

"Without active Notch signalling taking place, the worker bee eggs are now able to mature," he said.

"This contrasts with its role in fruit fly reproduction in which the signalling is vital for fertility."

It was not yet clear whether QMP worked directly on ovaries or was acting via signalling between the brain and antennae.

"However it is acting, the outcome is that Notch signalling's fundamental role in the ovary has been modified and transformed in honeybees into social control of worker bees' reproduction."

Honeybee loss would bring a big financial sting

Meanwhile, another new study has shown New Zealand agriculture stands to lose between $295 and $728 million each year if the local honeybee population continues to decline.

One of the co-authors of the study, Professor Stephen Wratten of Lincoln University's Bio-Protection Research Centre, said it was well known that a global decline in the populations of insect pollinators posed a major threat to food and nutritional security.

"We've lost most of our wild bees in New Zealand to varroa mite, and cultivated bees are becoming resistant to varroa pesticides," he said.

"Functioning beehives are becoming increasingly expensive for farmers to rent.

"We know the decline in bee populations is going to have a major impact on our economy, but we wanted to measure the impact."

Previous methods of estimating the economic value of pollination had focused on desktop calculations around the value of crops and the dependency of those crops on pollinators.

Professor Wratten said the experimental manipulation of pollination rates was a more direct estimation of the economic value of pollination, or ecosystem services (ES).

A study was conducted in commercial fields producing pak choi for seed production.

Some of the plants were covered with thin white mesh bags for varying time periods, preventing honeybees and fly species, which were key pollinators for the crop, from accessing the plants.

Changes in seed yield, seeds per pod and proportion of unfertilised pods as a result of changing pollination rates were identified.

The economic impact of varying pollination rates was then extrapolated to the main 18 pollination-dependent crops in New Zealand.

The economic impacts of loss of pollinators included higher prices for consumers as crop yields are reduced and food production costs increase.

"It's critical to understand marginal changes in ES and their economic consequences in order to identify appropriate policy responses and avert further losses," Professor Wratten said.

"Modifying existing agricultural systems to enhance ES requires a range of mechanisms, such as payments for ES.

"Current policies at a national and global level continue to largely ignore the value of ES contributions such as biological control and pollination."

Across the world, farmers needed help to put appropriate diversity back into their lands, he said.

"There is a lot of scientific knowledge accumulating but this has to be turned into 'recipes' for end users like farmers to understand and implement.

"The big challenge is to have a recipe that works. Give farmers the right seeds to plant. Make sure the bees get what they need.

"It's not about planting pretty flowers. It's the science that counts.

"The best way to deliver this is through what we might call 'farmer teachers' � farmers who understand and use the recipe, who will get out into the paddock and be listened to by other farmers."