Farmed bees used to pollinate crops in commercial greenhouses are interbreeding with the local bees – and the potential consequences could be dire.

Every year, more than 1 million commercially reared bee colonies are used in greenhouses around the world to help pollinate crops. But these are typically non-native bees and introducing them to new areas is risky. If they escape, they can compete with local bees for food and nesting resources. They can also spread mites, viruses and other diseases to native populations, says Sevan Suni at the University of San Francisco, California.

On top of all that, Ignasi Bartomeus at the Doùana Biological Station in Seville, Spain, and his colleagues suspected that the farmed bees may also interbreed with local bees and that this could cause further trouble. To investigate, the researchers captured 66 bees in the wild in Andalucía, Spain, and analysed their genes.

This showed that 63 per cent of the bees had hybridised with the commercial bees. Some of them were found 60 kilometres from the nearest greenhouse. This suggests that native and commercially bred bees are readily interbreeding.

The hybridisation can threaten the long-term survival of the native bees, says Bartomeus. “Diversity is the best insurance against [environmental] perturbations because it creates variability from which to adapt to new situations,” he says. “If we homogenise the genetic diversity of some species, we are losing this insurance.”

Bartomeus says that the commercial bees hibernate in the winter, while the native bees go into dormancy in the hot Mediterranean summer. “A potential threat is that southern bumblebees may lose their adaptations to warm environments – which is really critical given the climate warming trend we are experiencing,” he says.

Bartomeus reckons that simply farming local species of bees and using those as pollinators instead of foreign ones would be one way to help prevent these problems.

Suni agrees that native bees can fill the pollinator role on farms. “We need to conserve and establish natural habitat around agricultural areas so that wild bees will have nesting sites, and so that they can contribute to agricultural pollination,” she says.

Reference:

The evidence has been mounting for years that the world’s most widely used pesticides, neonicotinoids, harm bees and other pollinating insects. Now it seems the problem isn’t limited to Europe and North America, where the alarm was first sounded. It’s everywhere.

In 2013 the EU temporarily banned neonicotinoids on crops that attract bees, such as oilseed rape. In November, the European Food Safety Authority will decide . .

Starting in 2012, a team led by of the University of Neuchâtel, Switzerland, asked travelling colleagues, friends and relatives to bring back honey when they went abroad. In three years they amassed 198 samples from every continent except Antarctica, and tested them for neonicotinoids.

They found that three-quarters of the samples contained at least one of the five neonicotinoid pesticides. Of those, nearly half contained between two and five different neonicotinoids.

Most worryingly, in 48 per cent of the contaminated samples, the neonicotinoids were at levels that exceeded the minimum dose known to cause “marked detrimental effects” in pollinators. “The situation is indeed bad for pollinators,” says Aebi.

It’s all around us

“Finding neonicotinoids in honey is perhaps not surprising,” says of the University of Dundee, UK. After all, the pesticides are widely used. “But to find neuroactive levels, in so many samples at many global sites, is shocking.”

Bees survive the winter by eating honey, so the results imply they are chronically exposed to neonicotinoids. “Recent scientific evidence showed an increased sensitivity to neonicotinoids after frequent or long-term exposure,” says Aebi.

The fact that the honey contained cocktails of neonicotinoids may also be a problem. They all act on different receptor proteins in the nervous systems of the insects. Some chemicals can boost each others’ toxic effects over time, says Connolly. However, there is only indirect evidence of this happening with the neonicotinoids so far.

Frustratingly, we have the data to figure out how real-world levels of the pesticides affect bees, but not in a useful form. Farmers in Europe and North America record their use of neonicotinoids, says Connolly, but this data needs to be gathered into geographical databases. Such databases could reveal local correlations between pesticide use and insect health. Aebi and his team are now urging governments to start collecting the data.

Infection protection

Apple trees pollinated by bumblebees exposed to neonicotinoid pesticides contained 36 per cent fewer seeds than those pollinated by unexposed bees.

The results are the first to show that neonicotinoids impair the insects’ ability to pollinate plants.

Previous studies have found that the controversial pesticides can affect bees and bumblebees, but haven’t measured whether it disrupts their ability to pollinate plants.

About 30 per cent of agricultural crops depend on pollination by insects or other animals, with an estimated global value to farmers of $360 billion a year.

“Our work highlights the importance of pollination services, and including that in the debate about whether to ban or restrict neonicotinoids is very important,” says of Royal Holloway, University of London.

Pollen decline

Stanley and her colleagues exposed colonies of bumblebees to nectar that either contained a type of neonicotinoid known as thiamethoxam at levels typically found in nectar and pollen from treated crops and contaminated wild flowers. The bees exposed to neonicotinoids collected less pollen from apple trees and visited apple flowers less frequently than the other group.

This behaviour resulted in a reduction in the number of seeds found in the apples, an important indicator of the extent of pollination.

For several years, debate has raged about the size of the effect neonicotinoids have on bees. A temporary moratorium on their use on certain crops pollinated directly by bees – such as oilseed rape – is in place in Europe while the European Food Safety Authority undertakes a review of all the evidence.

In the US, a court ruling in September overturned the US Environmental Protection Agency’s earlier approval of a newer type of neonicotinoid.

“With apples, we consumers don’t care if it has fewer pips, but it’s very important for apple growers as there is evidence linking the number of seeds with apple quality,” says Stanley. And if neonicotinoids are disrupting pollination of apples, they are likely to also be disrupting pollination of many other crops, including strawberries, raspberries, oilseed rape, field beans and peas, as well as wild flowering plants.

Artificial conditions

“The obvious conclusion is that farmers using these chemicals could potentially experience reduced crop yields, as could their neighbours who may not be using the chemicals,” says Dave Goulson of the University of Sussex, UK. “There may also be knock-on effects for pollination of wild flowers growing on or near farms.”

Syngenta, a company that manufactures thiamethoxam, says the design for the experiment, with bee colonies only allowed to forage for an hour a day and apple trees placed in experimental tunnels, didn’t represent real-life conditions.

This means the results are not conclusive, says Peter Campbell of Syngenta. “They are premature and only representative of a single experiment conducted under artificial conditions both for the apple trees being pollinated and the method of exposing the bumblebees,” he says.

Another paper published this week by French researchers found that while neonicotinoid pesticides harm individual honeybees, whole colonies were able to recover in the wild.

Mickael Henry of the French National Institute for Agricultural Research in Avignon and his team found that honeybees foraging around treated crops die off at a faster rate than normal – but colonies were able to make up by boosting the number of worker bees in the hive.

Journal reference: Nature, DOI: ; Royal Society journal Proceedings B; DOI:

Read more: “ Bitter sweet nectar: Why some flowers poison bees“; “Why insects are the real rulers of the world”

Image credit: Victoria Wickens

Evolving a knack for more compact flowers (Image: Christine Carson)

Two alpine bumblebee species, formerly picky eaters, are expanding their palates – by shortening their tongues.

As the climate warms, their homes near the peaks of the Rocky Mountains have fewer flowers than before. At Pennsylvania Mountain in Colorado, for example, the number of flowers the bees feed on has dropped by 60 per cent since the 1970s.

So the bees have become less choosy, evolving to sip nectar from a wider variety of flowers: Bombus balteatus and B. sylvicola tongues have become 25 per cent shorter over the last 40 years or so.

“Natural selection can give them running shoes to keep up with climate change,” says of the University of Missouri in Columbia, whose team compared bumblebees collected in 2012-2014 with museum specimens from 1966 to 1980.

They found that the shortening of tongues was not the result of bees or flowers getting smaller, but because flower numbers have dropped dramatically as warmer temperatures linked to less prolific blossoming have become more common.

Long tongues originally helped the bees specialise on those flowers whose nectar was out of reach for insects with shorter tongues.

Long straw, small cup

But long tongues come with a cost: they take extra energy to grow and can be cumbersome for feeding on shorter flowers. “Imagine you have a really long straw and you’re trying to stick it in this really small cup,” says at North Carolina State University.

In recent years the bumblebees have had to rely more and more on those shorter flowers. The costs of sporting long tongues now seem to outweigh the benefits, so natural selection has favoured bees with shorter tongues.

Their ability to adapt in these alpine habitats is good news, because bumblebees’ natural habitats are being squeezed by climate change.

Bumblebees are especially important pollinators as they can live in places that honeybees cannot, such as at high elevations. Also, because bumblebees are much fuzzier than honeybees – Irwin likens them to a furry animal you could pet – they carry more pollen and are more efficient pollinators.

Irwin says bumblebees are vital to the grass-fed beef and dairy industries. “Our native bees are critically important to conserve,” she says.

Galen says the work shows that evolution can equip bumblebees with tools to survive in a changing climate, if they are able to find a haven free from pesticides and habitat disruption.

Journal reference:

Bumblebees, including the red-belted bumblebee, don’t do well in the heat (Image: Jeremy T Kerr)

Bumblebee habitat in North America and Europe is rapidly being lost. What’s more, the cool-loving insects are succumbing to rising temperatures in the south without shifting north.

The fear is that many species vital for pollinating crops and wild plants on which entire ecosystems depend may be pushed to extinction.

“We are looking at what we think is a first for global warming, that in the north, bumblebee species are failing to extend their range northward while their southern range contracts,” says of the University of Ottawa in Ontario, Canada.

“Their distribution has run up against a kind of wall, because they’re not establishing new territory fast enough to track the rapid changes in temperature.”

Other species manage

Kerr says that many other species including fish and butterflies have successfully managed to shift their ranges northward, but bumblebee ranges across Europe and North America have receded by 300 kilometres in the south in the past three decades without a corresponding increase to the north.

“It’s crushing bumblebee species in a kind of climate vice,” says Kerr.

Kerr and his colleagues say that the situation is so dire that governments and conservation agencies should consider artificially creating colonies to the north to help them spread, a process called assisted migration. “We need governments to lead strongly on this, and we need it immediately,” says Kerr.

Kerr and his colleagues analysed more than 420,000 records of bumblebee sightings and activity between 1901 and 2010, and covering 67 species – 31 in North America and 36 in Europe.

They used the data from 1901 to 1974 as a baseline to see how rapidly rising temperatures since then had affected ranges.

Despite a significant rise in temperatures, bumblebees have failed to track north to escape the heat further south, clipping an average of 300 kilometres from the southern limits of their ranges as a result compared with the baseline.

Kerr thinks that bumblebees are being wiped out in the southern limits of their range before they can migrate.

Besides changes in climate, the team also considered the potential impacts of habitat loss and insecticides, including neonicotinoids, on bumblebees.

Governments must act

Unlike other insects such as butterflies, which evolved in the tropics and can handle heat, bumblebees evolved in temperate environments and simply don’t have the bodily machinery to survive the heat waves becoming more common as the planet warms up.

“They don’t have the capacity to withstand heat shock and so are fairly intolerant to sustained hot conditions,” Kerr says.

“They’ve had plenty of opportunity to move northwards, so it’s very hard to see why they haven’t,” says , a bee specialist at the University of Sussex, UK. “My guess is that the habitat they need is not available.”

The failure to relocate is a big puzzle, says Kerr. It might be that the bees do head north, but cannot grow their populations fast enough to establish, he thinks.

That is why he thinks they need human help to relocate.

“We’re only talking about moving species a little further north,” he says, arguing that a small shift would not amount to making the bees into invasive species.

Journal reference: Science, DOI: 10.1126/science.aaa7031

I could really do with a drink (Image: Prisma Bildagentur AG / Alamy)

They like their meat, genets and mongooses do, but they also like to wash it down with a slug of flower nectar every now and then.

, from the University of Cape Town, South Africa, and her team set up multiple motion and infrared sensor cameras in the shrubland of the Western Cape, to monitor how mammals interact with the flowers of the sugarbush plant.

Rhabdomys: a frequent visitor to sugarbush plants (Image: Alice Balmer)

There are around 30 species of sugarbush or Protea and they are pollinated by small ground-dwelling mammals, such as rodents and elephant shrews, which the team recorded visiting the flowers, alongside birds.

But the large-spotted genets and Cape grey mongooses were something of a surprise. The genets accounted for around 7 per cent of all recorded visits to the flowers by mammals and bird, and the mongoose for around 4 per cent.

“These genets and mongooses appeared quite keen on the nectar and visited flowers repeatedly, even if it meant climbing a few branches or foraging during light snow,” says Steenhuisen.

Both animals, though, are mainly meat and arthropod eaters, even though they occasionally feed on plants. Steenhuisen thinks they visit flowers for the sugar kick.

Sugary snacks

“These flowers produce nectar containing over 30 per cent sugar by weight, a rich sugary snack for any visitor,” she says.

Her team also observed pollen on the carnivores’ snouts and think the carnivores are pollinating the flowers, so the behaviour benefits both the animals and plants.

Given that their visits to flowers are rare compared with visits of other animals, from the University of DĂźsseldorf, Germany, thinks these animals only play a minor part in pollination, if at all.

But Steenhuisen says these larger species regularly travel longer distances than small rodents, so they may help disperse pollen further away. “Their home ranges are much larger than those of rodents, the more common visitors to these plants. So, although their visits may be infrequent, they may play a small important part in out-crossing plants far away from each other,” she adds.

The remaining puzzle is what makes the sugarbush flowers so attractive to all these different mammals – rodents, elephant shrews, genets, mongooses – with diets ranging from seeds, insects and meat.

“These unrelated animals have different diets, so it’s a puzzle as to what kind of common attractive signal is being emitted by these plants,” says Steenhuisen.

The flowers have a strong fermented smell, resembling sour milk or cheese. So, she thinks one possibility is that compounds in the smells that signal a source of fermenting sugar or protein may be innately attractive to all these mammals.

Journal reference: African Journal of Ecology, DOI:

European allergy sufferers resigned to the perennial springtime blitz on their noses may need to keep their tissues handy later in the year too. An invasive plant from North America that releases copious amounts of allergenic pollen in the autumn looks set to massively expand its range in Europe.

What will drive the spread of common ragweed (Ambrosia artemisiifolia) is a combination of climate change and accidental dispersal of its seeds.

In Europe, ragweed is most commonly reported in areas of northern Italy and southern France. But computer modelling predicts that by 2050 it will be found in parts of eastern and northern Europe, including Germany, Ukraine, Romania, the UK and the rest of France.

“Ragweed will continue to invade Europe, and the airborne pollen concentrations will by 2050 increase by a factor of 4 on average,” warns Lynda Hamaoui-Laguel of the Laboratory of Climate Science and the Environment in Gif-sur-Yvette, France, whose team produced the computer simulations. “Seed dispersal will increase mainly through transport – mainly along roads by agricultural equipment – and also via waterways and by contaminating consignments of commercial seeds,” she says.

Meanwhile, rising temperatures will also make areas of eastern and northern Europe ripe for a ragweed invasion. Longer summers will mean more ragweed plants will complete their life cycle and produce mature seeds, and extra carbon dioxide in the atmosphere will nourish the plants, helping them produce even more pollen.

Ragweed is abundant in North America, where a quarter of the population are sensitised to it. It is the third largest allergy trigger, fractionally behind dust mites and rye grass pollen. As few as 20 ragweed pollen grains per cubic metre of air can provoke an allergic response, and actual concentrations can be 10 times that.

“It’s most likely to affect those who already suffer from hay fever and react to pollen from our native trees, particularly birch, and to grass and weed pollens,” says Maureen Jenkins, clinical director of the charity, Allergy UK. “This would add to the severity of their symptoms and will extend the length of time they suffer the debilitating effects of this disease.”

Hamaoui-Laguel says the only way to prevent ragweed’s advance through Europe is through a coordinated program of uprooting and destroying as many of the plants as possible before they flower.

Journal reference: