The effects of transgenic rape pollen on bees

Summary

All of the bee species under investigation collected transgenic rapeseed pollen from the test sites and fed it to their broods. While the proportion of transgenic pollen collected by the honeybee and the earth bumblebee was around three percent, the mason bee collected up to eleven percent transgenic pollen. The research also showed that a buffer strip of conventional rapeseed is not enough to limit the distance that pollen spreads.

Even at a distance of 100 metres, 30 percent of the brood cells of the mason bee contained transgenic rapeseed pollen, which means that bees collect pollen from distant fields. The proportion of transgenic pollen in the diet of mason bee larvae feed amount to 1.6 percent at a distance of 25 metres and 0.8 percent at a distance of 100 metres.

Experiment description

Colonisation by bees

At the beginning of the experiment, earth bumblebee and mason bee hives were established with nest boxes at a field trial site in Dahnsdorf, Brandenburg.

Transgenic rapeseed pollen in the bees’ diet

Pollen was collected for analysis either by taking samples of the pollen brought into the hives or by removing pollen from foraging bees. Samples were taken at three time periods: at the start of rapeseed flowering, during peak flowering, and near the end of the flowering period. The pollen was prepared for analysis and checked with a microscope to determine the proportion of the pollen that came from rapeseed. When rapeseed pollen was identified, the respective proportion of transgenic pollen was determined by transgene targeted quantitative PCR . A higher proportion of transgenic DNA increases the likelihood of gene transfer to microorganisms in the digestive tract of bees.

Further research was carried out into the effects of a 7.5 metre buffer strip of conventional rapeseed surrounding the GM planting. In 2003, mason bee colonies were established at distances of 25 and 100 metres from the transgenic rapeseed planting. Brood cells were tested to see if the buffer strip was effective at reducing the proportion of transgenic pollen contained in the diet of larvae.

Tests for horizontal transfer

In addition, part of the digestive tract of collected bee larvae and adults (fully grown bees) were to be prepared for tests on horizontal gene transfer to microorganisms. 

Results

From 2001 to 2003, several honeybee, bumblebee, and mason bee colonies were set up in close proximity to a transgenic rapeseed test planting. ollen, larvae, and foraging adults that were collected for study.

Transgenic rapeseed pollen in the diets of bees

The proportion of transgenic rapeseed pollen in the diet of the bees varied depending to the phase of flowering and the bee species.

Only a few individuals among the honeybees and the earth bumblebees collected pollen from the transgenic rapeseed planting. Many of them flew to more distant fields. Only a maximum of 30 percent of pollen sacks contained transgenic pollen.

When present, the transgenic pollen represented varying proportions of the pollen in an individual’s pollen sack. Even with honeybees, which tend to stick to a particular area, there were no pollen sacks that contained exclusively transgenic pollen. This can be attributed to the small size of the test planting, one third of which was planted with conventional rapeseed. The researchers came up with an average proportion of rapeseed pollen brought back to the colonies for each of the species. For the honeybee, transgenic rapeseed pollen accounted for 0.1 to 0.3 percent of the pollen brought back to the hive. For the bumblebee, it accounted for 3.4 percent of the total pollen.

In contrast, the feed in the individual brood cells of mason bees showed a much higher presence of transgenic rapeseed pollen. It was found in up to 90 percent of the cells, which required an average of 12 to 34 collection flights to fill. Transgenic pollen collected by the mason bees came to between 0.6 and 11 percent of the total pollen, depending on the year and the time of collection.