European dark bee. Video: WUR
A remarkable species is kept frozen at the Centre for Genetic Resources (CGN) of Wageningen University & Research: the European dark bee. In collaboration with various other organisations, the CGN strives to preserve the only indigenous bee species in the Netherlands, for a future with robust agriculture and a high degree of biodiversity.
Bees are one of the few production animals that also have a presence in the wild. The foreign and specially bred subspecies that are popular with beekeepers feature the characteristic dark and yellowish stripes and are highly industrious producers of honey. While these bees are not native to the Netherlands, they are now universally present. The island of Texel is an exception to this rule, since the beekeepers there keep a different species: Apis mellifera mellifera, also known as the European dark bee. he European dark bee is a subspecies of the Western honey bee (Apis mellifera), which has a total of 25 subspecies all over the world. The European dark bee is indigenous to a wide strip running from France to the depths of Russia, and was kept by beekeepers until the middle of the 19th century. After this, many foreign, specially bred subspecies were introduced in the Netherlands, two of which now dominate the Dutch beekeeping sector: the Carniolan honey bee, which traces its origins to the Balkan, and the Buckfast bee, bred by an English beekeeper. Meanwhile, only about 150 out of 90,000 bee colonies in the Netherlands are made up by the European dark bee.
Left: Sections of the honeycomb containing the drones are cut out at the beekeepers' hives on Texel. Photo: WUR Right: In the lab, researchers remove the drone pupae from the comb and isolate the DNA. Photo: WUR
For most livestock, the species kept by your neighbour doesn’t present much of a problem. Things get a little more complicated with bees, though. After all, they can fly. All subspecies of the honey bee can successfully cross-breed. Due to the resulting hybrids, the unique DNA of the European dark bee is lost, as are its characteristic properties. According to Annemieke Rattink of the Centre for Genetic Resources (CGN), part of WUR, this is a serious problem. ‘The European dark bee has adapted to our indigenous flora and fauna and plays an important role in pollinating flowers. This means this little critter is important for our biodiversity.’
Frozen biological heritage
The Centre for Genetic Resources stores the DNA of dozens of species of rare domestic animals, crops, bushes, trees, shellfish and fish, often in the form of frozen sperm. The oldest container of sperm dates from 1959. The freezing process keeps the sperm cells viable, so they can be reused in research or breeding projects at a later date. For example, the sperm of a bull, frozen in 1970, was successfully used over fifty years later for the conception of a healthy calf.
'The European dark bee is therefore important for our biodiversity'
The dark bee is a native bee species that used to be universal to the Netherlands, but can nowadays only be found on Texel. The preservation of this species is important for biodiversity conservation. But how pure is the Texel bee really? Researchers of the Centre for Genetic Resources, part of Wageningen University & Research, are currently investigating this.
‘At the CGN, we store our biological heritage’, Rattink explains. ‘Back in the day, there was far greater variation in domestic animals, with species that were well adjusted to life in various landscapes. These days, agriculture has become highly uniform, which means most dairy farmers keep the same type of cow. This makes our agricultural sector more susceptible to disease and the effects of climate change.’ Over the past years, the government’s vision regarding agriculture has been changing. ‘In the future, the interests of nature and agriculture should align more. This means the older species may become more interesting to farmers operating in the native areas of those species.’
A strong population is both pure and diverse
he European dark bee is the first insect in the collection of the CGN. That’s why Rattink and her colleagues now seek to find out whether there are still any pure dark bees in the Netherlands, i.e. bees without any DNA from other subspecies. This brought them to Texel, where the municipal council has been working to preserve the dark bee for 40 years. The sea surrounding the island already formed a natural barrier, and an import ban on foreign bee species was declared to keep out bee diseases. As a result of this, they managed to preserve the European dark bee in the Netherlands. To this day, beekeepers on Texel are only allowed to keep European dark bees. In the spring of 2024, Rattink and her colleague, Menno Diersmann, travelled to Texel to gather DNA from European dark bees on the island. They took some larvae from each of the colonies kept by the island’s 17 beekeepers and delivered them to the CGN for genetic analysis. ‘Genetic research is needed to find out how pure the European dark bee on Texel actually is’, Rattink explains. ‘On top of this, we are trying to find out more about the diversity of the population, and if there are signs of inbreeding. The queens on Texel may be closely related, which weakens the population.’ At the beginning of 2025, the researchers expect to be able to provide a definitive answer.
‘At the CGN, we store our biological heritage’
Left: Ultimately, the sperm from the most genetically diverse populations will be stored in the CGN gene bank, in tanks with liquid nitrogen. Photo: WUR
The next step is selecting the most diverse and pure colonies from which to collect bee sperm. However, before this can be done, the researchers need to find out the best way to freeze bee sperm. Rattink: ‘The protocol for freezing sperm is different for each species. There is very little margin for error here, or you risk killing the sperm cells and making them unusable.’ As soon as the protocol is established, the researchers will once more travel to Texel to capture several drones from the selected colonies and harvest their sperm.
Nature-inclusive agriculture works better with indigenous species
For this project, Rattink is collaborating with the Nederlandse Bijenhoudersvereniging (Dutch Beekeeper’s Association), the Stichting Duurzame Bij (Sustainable Bee Foundation) and the Stichting Zeldzame Huisdierrassen (Rare Domestic Animals Foundation) (SZH), which supports keepers of rare domestic animals and tries to motivate new ones. Nonja Remijn, office coordinator of SZH, explains why: ‘Some old agricultural species are only kept by a small number of people. It would be a shame if they were to disappear. The old agricultural species are often a good fit for organic farming, for farmers whose animals graze in nature reserves and for farmers aiming to make their business more circular. The opportunities for these indigenous species in nature-inclusive agriculture are growing ever larger.’ An example? ‘Some cattle breeds and certain chickens thrive in orchards. As a honey bee and pollinator, the European dark bee is the perfect addition to this little ecosystem.’
Right: Dark bee. Photo: Shutterstock
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