Plants use advertising-like strategies to attract bees with colour and scent


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A honeybee (left), a scarab beetle (middle), and a fly (right) feeding on flowers of the white rock rose in a Mediterranean scrubland.
Aphrodite Kantsa., Author provided

Aphrodite Kantsa, University of the Aegean and Adrian Dyer, RMIT University

Watching plants and pollinators such as bees can teach us a lot about how complex networks work in nature.

There are thousands of species of bees around the world, and they all share a common visual system: their eyes are sensitive to ultraviolet, blue and green wavelengths of the light spectrum.

This ancient colour visual system predates the evolution of flowers, and so flowers from around the world have typically evolved colourful blooms that are easily seen by bees.

For example, flowers as perceived by ultraviolet-sensitive visual systems look completely different than what humans can see.

However, we know that flowers also produce a variety of complex, captivating scents. So in complex natural environments, what signal should best enable a bee to find flowers: colour or scent?

Our latest research uncovered a surprising outcome. It seems that rather that trying to out-compete each other in colour and scent for bee attention, flowers may work together to attract pollinators en masse. It’s the sort of approach that also works in the world of advertising.




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Daunting amount of field work

Classic thinking would suggest that flowers of a particular species should have reasonably unique flower signatures. It makes sense that this should promote the capacity of a bee to constantly find the same rewarding species of flower, promoting efficient transfer of pollen.

So a competition view of flower evolution for different flower species with the same colour – for example purple – would suggest that each flowering plant species should benefit from having different scents to enable pollinator constancy and flower fidelity. By the same logic, flowers with the same scents should have different colours so they’re easily distinguished.

To know for sure what happens requires a daunting amount of field work. The challenges include measuring flower colours using a spectrophotometer (a very sensitive instrument that detects subtle colour differences) and also capturing live flower scent emissions with special pumps and chemical traps.

A wild bee of the genus Anthophora upon making the decision to visit the flowers of purple viper’s bugloss, in a Mediterranean scrubland in Greece.
Aphrodite Kantsa.

At the same time, in order to record the actual pollinator “clientele” of the flowers, detailed recordings of visits are required. These data are then built into models for bee perception. Statistical analyses allow us to understand the complex interactions that are present in a real world evolved system.

Not what we thought

And what we found was unexpected. In two new papers, published in Nature Ecology & Evolution and in Nature Communications, we found the opposite to competition happens: flowers have evolved signals that work together to facilitate visits by bees.

So flowers of different, completely unrelated species might “smell like purple”, whilst red coloured species share another scent. This is not what is expected at all by competition, so why in a highly evolved classical signal receiver has this happened?

The data suggests that flowers do better by attracting more pollinators to a set of reliable signals, rather than trying to use unique signals to maximise individual species.

By having reliable multimodal signals that act in concert to allow for easy finding of rewarding flowers, even of different species, more pollinators must be facilitated to transfer pollen between flowers of the same species.




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Lessons for advertising

A lot of research on advertising and marketing is concerned with consumer behaviour: how we make choices. What drives our decision-making when foraging in a complex environment?

While a lot of modern marketing emphasises product differentiation and competition to promote sales, our new research suggests that nature can favour facilitation. It appears that by sharing desirable characteristics, a system can be more efficient.

This facilitation mechanism is sometimes favoured by industry bodies, for example Australian avocados and Australian honey. En masse promotion of the desirable characteristics of similar products can grow supporter base and build sales. Our research suggests evolution has favoured this solution, which may hold important lessons for other complex market based systems.

A successful colour–scent combination targeted at attracting bees can be adopted by several different plant species in the same community, implying that natural ecosystems can function as a “buyers markets”.




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We also know from research that flowers can evolve and change colours to suit the local pollinators. Colours can thus be changed by flowers if instead of bees pollinating flowers, flies, with different colour perception and preferences, dominate the community.

These findings can also prove useful for identifying those colour-scent combinations that are the most influential for the community. This way, the restoration of damaged or disrupted plant-pollinator communities can become better managed to be more efficient in the future.

The ConversationWhen next enjoying a walk in a blooming meadow, remember plants’ strategies. The colourful flowers and the mesmerising scents you experience may have evolved to cleverly allure the efficient pollinators of the region.

Aphrodite Kantsa, Postdoctoral Researcher, University of the Aegean and Adrian Dyer, Associate Professor, RMIT University

This article was originally published on The Conversation. Read the original article.

Pesticide bans might give us a buzz, but they won’t necessarily save the bees


Caroline Hauxwell, Queensland University of Technology

Public pressure is growing in Australia to ban the sale of pesticides called neonicotinoids because of their harmful effects on bees.

The retail chain Bunnings will stop selling the Confidor pesticide brand for homes and gardens by the end of 2018.




Read more:
Ten years after the crisis, what is happening to the world’s bees?


Neonicotinoids along with fipronil, another systemic insecticide that has also been blamed for bee deaths, are widely used in Australia on major crops such as maize, canola and cotton.

Between them they account for up to 30% of global insecticide sales. Will banning these insecticides stop the decline of bees worldwide?

Mites and disease

Insects are in trouble. A recent study found an 80% decline in flying insects, including butterflies, moths and wild bees, in German nature reserves. This has prompted questions about the impact of large-scale intensive agriculture.

Colony collapse disorder, in which worker bees dramatically disappear from honey bee hives, increased hugely in the decade up to 2013, particularly in the United States and Europe. This caused international concern and led to a ban on neonicotinoids and fipronil by the European Union in 2013.




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However, there are no reports of colony collapse disorder in Australia, according to the Australian Pesticides and Veterinary Medicines Authority, which regulates the use of pesticides and monitors the effect of insecticides on bees. Why not?

We don’t fully understand the causes of colony collapse in honey bees, but it appears that a likely culprit is the Varroa mite and the lethal viruses it transmits. This parasite feeds on both larvae and adult bees, and has been blamed for infecting vast numbers of bees with several viruses including deformed wing virus.




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Australia’s honey bees, in contrast to the rest of the world, are still free of Varroa mites. A CSIRO survey of 1,240 hives across Australia found that deformed wing virus is also not present. The absence of both the mite and the viruses it carries may help to explain why colony collapse has not (yet) been observed in Australia.

Pesticide and fungicides, oh my!

While there is clear evidence of harm to bees from the use of neonicotinoids and fipronil, particularly from drift during application, their role as the direct cause of colony collapse is not proven.

And while they can be harmful, neonicotinoids are not necessarily the biggest chemical threat to bees. Perhaps surprisingly, fungicides appear to be at least as significant.

One study found that bees that eat pollen with high levels of fungicide are more likely to be infected with a pathogen called Nosema. Other research showed that presence of the fungicide chlorothalonil was the best predictor of incidence of Nosema in four declining species of bumblebees. What’s more, the toxicity of neonicotinoids to honey bees doubles in the presence of common fungicides.

This is not to say that Australian bees are safe, or that neonicotinoids are not harmful. Australia has more than 5,000 native bee species, and studies suggest that the main impacts of neonicotinoids are on wild bees rather than honey bees in hives. The combination of widescale use of multiple agrochemicals, loss of plant and habitat diversity, and climate change is a significant threat to both wild and domesticated bees.

And if the Varroa mite and the viruses it carries were to arrive on our shores, the impact on Australia’s honey bees could be catastrophic.

Banning pesticides affects farmers

The EU insecticide ban left Europe’s farmers with few alternatives. Surveys of 800 farms across the EU suggest that farmers have adapted by increasing the use of other insecticides, particularly synthetic pyrethroids, as well altering planting schedules to avoid pests, and increasing planting rates to compensate for losses. Most farmers reported an overall increase in crop losses, in costs of crop protection and in time needed to manage pests.

A ban on fipronil and neonicotinoids would create similarly significant problems for Australian farmers, increasing costs and reducing the efficacy of crop protection. As in Europe, they would potentially increase use of synthetic pyrethroids, organophosphates and carbamates, many of which are even more harmful to bees and other insects.




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Reliance on a more limited range of insecticides could also worsen the incidence of insecticide resistance and destabilise Australia’s efforts to balance resistance management and pest control with preserving beneficial insects.

Further development of these sophisticated pest management strategies, with emphasis on the use of less harmful alternatives such as microbial and biological controls, offers a route to a more effective, long-term solution to the decline in insects and bee health.

The ConversationA ban on neonicotinoids might give campaigners a buzz, but it might not save the bees.

Caroline Hauxwell, Associate Professor, Queensland University of Technology

This article was originally published on The Conversation. Read the original article.

Ten years after the crisis, what is happening to the world’s bees?



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Bees have been living with the mysterious Colony Collapse Disorder for a decade.
Simon Klein, Author provided

Simon Klein, Université de Toulouse 3 Paul Sabatier and Andrew Barron, Macquarie University

Ten years ago, beekeepers in the United States raised the alarm that thousands of their hives were mysteriously empty of bees. What followed was global concern over a new phenomenon: Colony Collapse Disorder. The Conversation

Since then we have realised that it was not just the US that was losing its honey bees; similar problems have manifested all over the world. To make things worse, we are also losing many of our populations of wild bees too.

Losing bees can have tragic consequences, for us as well as them. Bees are pollinators for about one-third of the plants we eat, a service that has been valued at €153 billion (US$168 billion) per year worldwide.

Ten years after the initial alarm, what is the current status of the world’s bee populations, and how far have we come towards understanding what has happened?

The current status of bees worldwide

Since the alarm was first raised, many countries have created new monitoring methods to judge the status of their bee stocks. As a result we have much more data on bee populations, although coverage is still patchy and differences in survey methods make it hard to compare between continents.

It is clear that bees in the United States are still struggling. Beekeepers can tolerate up to 15% losses of colonies over winter, but the US is massively above this threshold, having lost 28.1% of colonies over the 2015-16 winter.

Canada, by contrast, reported 16.8% losses. This is better, but still above the level of losses at which beekeepers can easily restock.

Only recently have we had data from central Europe. There, honey bees seem to be doing better: 11.9% losses in 2015-16. Meanwhile, in New Zealand surveys only began in the last year and have reported winter loss of 10.7%. Australia does not yet have a countrywide survey of the state of bee colonies.

Fortunes are mixed for bees around the world.
Simon Klein, Author provided

Honey bees are not the only bees that we should care about: wild bees are vital pollinators too. Some plants are pollinated by only one wild bee species, such as the macropis bees that forage on the loosetrife plant.

Unsurprisingly, we have much less data on wild bees than honey bees, and those data we do have point to bigger concerns. For our wild bees we only really have good data for populations that are endangered or that have completely disappeared. Between 2008 and 2013, wild bee diversity in the US dropped by 23%, and a previously common bumblebee species was recently listed as endangered.

Do we understand why?

The good news is that the past decade has seen plenty of progress in understanding the mystery of Colony Collapse Disorder. The bad news is that we now recognise it as a complex problem with many causes, although that doesn’t mean it is unsolvable.

For all bees, foraging on flowers is a hard life. It is energetically and cognitively demanding; bees have to travel large distances to collect pollen and nectar from sometimes hard-to-find flowers, and return it all to the nest. To do this they need finely tuned senses, spatial awareness, learning and memory.

Anything that damages such skills can make bees struggle to find food, or even get lost while trying to forage. A bee that cannot find food and make it home again is as good as dead.

Because of this, bee populations are very vulnerable to what we call “sublethal stressors” – factors that don’t kill the bees directly but can hamper their behaviour.

For solitary species such as the blue-banded bee, difficulty foraging can be a very serious problem.
Simon Klein, Author provided

In a recently published review, we argue that modern agriculture and industry have created a host of sublethal stressors that damage bees’ cognition. For example, diesel fumes and neonicotinoid pesticides both reduce bees’ foraging efficiency by disturbing chemical communications in their brains. Modern intensive agriculture disturbs bee nutrition, which impairs their brain. Climate change interferes with the relationship between bees and the plants on which they feed.

In addition, managed honey bees are afflicted by a range of pests, viruses and predators that have been spread around the world as a side-effect of international trade. The worst is the ominously named Varroa destructor mite, which causes brain development disorders.

What can we do?

At the global level, to preserve our bees we have to improve the environments in which they collect food. Every small action can make a difference. Planting flower borders with bee-friendly flowers in your garden can provide food for both wild and domestic bees. You can reduce or eliminate the use of herbicides or pesticides when gardening. Even mowing the lawn less often can help bees out.

You could install a native bee hive or insect hotel. Another tempting option is to buy local honey, which often has a more distinctive flavour than mass-produced versions.

In Australia, we are fortunate in that our bees seem to be doing better than many other parts of the world. The Varroa mite has not yet invaded our shores, and in many areas bees can access pesticide-free bushland (although unlike Europe, Australia has not yet banned use of neonicotinoids in agriculture).

Australia also has an incredibly rich diversity of wild native bees: up to 1,600 different species, including our emblematic stingless bees. Even so, to protect this diversity we need better surveys of how these species are doing.

Ten years on from the alarm over disappearing bees, it is fair to say we now know the nature of the problem and what can be done to fix it. It’s up to us to take the steps needed to sustain these precious pollinators of our food for the future.

Simon Klein, Doctorant, Université de Toulouse 3 Paul Sabatier and Andrew Barron, Associate Professor, Macquarie University

This article was originally published on The Conversation. Read the original article.

Ants, bees and wasps: the venomous Australians with a sting in their tails


David Yeates, CSIRO

The prize for the most painful and sometimes deadly (more on that later) stings in the insect kingdom goes to … wasps, bees and ants.

There are many insects that bite, such as beetles and dragonflies, or suck your blood with long hypodermic mouthparts (mosquitoes, for instance, and sandflies). But none of these are deadly in themselves.

Mosquitoes do transmit deadly diseases, such as malaria and dengue. But it’s not the mosquito bite as such that kills; it’s the tiny parasitic microorganism that the mosquito transmits.

It’s really bees, wasps and ants – a group known as Hymenoptera – that can claim the title of deadliest insects. How did they evolve to be so painful?

How insects stings evolved

Many wasps are parasitic and developed long pointy hypodermic needles (or ovipositors) to inject their eggs into their hosts. Over evolutionary time, some of these parasitic wasps changed their lifestyle and became predatory. Some even went on to feed on pollen and nectar (bees).

A worker bee can sting a person only once.
吉輝 温/Flickr, CC BY-NC-ND

What happened to the ovipositor when wasps no longer needed to inject eggs? It became a pointy sting, a device for subduing prey with venom, as well as laying eggs.

It’s important to remember that only female wasps, bees and ants can sting; males don’t have the right apparatus.

Many of these stinging wasps, bees and ants have also become highly social insects. This means they live in large colonies such as honeybee hives, or ant nests. In these colonies, generally only a pair (a queen and a male drone, in the case of honeybees) or a few individuals reproduce.

All the rest are genetically and anatomically sterile females, and they do all the work inside and outside the hive or nest. These workers no longer need an ovipositor to lay eggs and it has become their primary weapon of choice, solely devoted to defence of the nest.

Workers use the sting to defend the wasp or bee nest, or ant colony. Queen bees lay eggs with their ovipositor and can also sting, but are usually tucked away in the nest far from harm.

Worker bees can sting humans only once – their barbed sting lodges in our skin and doesn’t retract, so the entire sting and the poison gland breaks free from the bee when it stings. The worker bee dies soon after and releases alarm pheromone, which alerts other workers that the nest is under threat.

A very good way of provoking a large number of European (or any other) wasps is to disturb their nest.
Ziva & Amir/Flickr, CC BY-NC-ND

More bees sting and release more alarm pheromones, attracting more alarmed bees … you get the picture. If you’re stung, remove the sting as soon as possible – this minimises the amount of venom injected.

A very small number of people (about one or two in every 100) can become hypersensitive after a bee sting. They become allergic to the venom, and their reaction becomes stronger when stung in future.

A highly allergic person may suffer anaphylactic shock from the sting, which can be life-threatening and requires medical treatment. A self-injecting EpiPen containing adrenalin is used to treat anaphylactic shock.

The most painful

Another common introduced stinger in Australia is the European wasp, Vespula germanica. This wasp’s sting doesn’t get stuck in our skin, so they can inflict multiple stings when annoyed or provoked. A very good way of provoking a large number of European (or any other) wasps is to disturb their nest – never do this.

A very small percentage of people can also develop an allergic reaction to European wasp stings, just like honeybee stings. In severe cases, this can cause anaphylactic shock.

Arizona entomologist Justin O. Schmidt developed the Schmidt Pain Index 30 years ago to rank the painfulness of wasp, bee and ant stings on a four-point scale.

Zero on the Schmidt pain index is the feeling of an insect that can’t sting you, such as Australia’s native stingless bees. Two is the familiar pain of a honeybee. Four is reserved for just a few heavy hitters, such as a very large spider-killing wasp, or the infamous bullet ant (Paraponera clavata) of South America.

The notorious and excruciating pain of the bullet ant lasts for 24 hours. Schmidt has been stung by more than 100 insects to create his scale, and was awarded the 2015 Ig Nobel Biology Prize for his efforts.

Some of the most common painful stingers in the Australian bush are native bulldog ants of the genus Myrmecia. These are some of the largest ants in the world and combine a painful sting with an aggressive, take-no-prisoners attitude. On top of this, many species can jump. They rate up to three on the Schmidt Pain Index.

Bulldog or jack-jumper ants have impressive long, toothed and curved jaws, but it’s the sting at the end of their abdomen that does the damage.

My most painful memory as a boy was annoying a bulldog ant nest in the Sydney bushland with a stick. Eventually a huge worker bulldog ant crawled up out of sight underneath my stick and gave me a sting on the thumb I thoroughly deserved – and will never forget.


This article is the last of our series Deadly Australia. You can see the whole series here.

The Conversation

David Yeates, Director of the Australian National Insect Collection, CSIRO

This article was originally published on The Conversation. Read the original article.

Losing bees will sting more than just our taste for honey


Marianne Peso

Changing wildlife: this article is part of a series looking at how key species such as bees, insects and fish respond to environmental change, and what this means for the rest of the planet.

We may lose a lot more than honey if bees are unable to cope with the changing climate and increasing demand for agricultural land.

Your morning coffee might be a thing of the past if bees disappear, and if coffee isn’t your thing, you undoubtedly eat many of the fruit and vegetables (and chocolate) that rely on bee pollination for survival.

In fact, the world’s 25,000 bee species are responsible for pollinating a third of the food humans eat. If we lose bees, then we risk the food security of ourselves, and all the other animals that depend on bee-pollinated crops for survival.

While European (managed) honey bees steal the limelight, other wild (non-honey) bees are just as important for pollinating crops and will also be impacted by climate change. Data from all over the globe suggest that both groups are in decline, but since we do not have a global integrated and complete monitoring system of bee populations, these data do not describe the full extent of the problem.

So how well equipped are bees to survive a warming climate, and is there anything we can do to help?

Bees and plants: it’s a long-term relationship

Bees and flowering plants share a long evolutionary relationship and depend on each other for survival. Plants provide bees with food and habitat, while the bees feeding on pollen and nectar provide the plants with pollination.

To orchestrate this beautiful exchange, plants and bees rely on environmental cues (such as temperature) to coordinate their seasonal activity. However, climate change can disrupt these relationships so that bee activity periods will no longer time with flowering periods. This will cause the bees to lose a food source and plants that fail to fruit, potentially leading to extinctions of both.

The beautiful exchange between bees and plants

Some plant-bee relationships are highly specialised. These species have evolved together so closely that a plant can depend on a single bee species in order to reproduce and vice versa.

Bees in specialist plant-bee relationships (such as this one) are most susceptible to climate induced extinction, as the loss of one will inevitably lead to the loss of the other.

More generalist bee species, that can collect food from more than one plant species, may fare better than their specialist counterparts. As the climate changes, animals and plants evolve new genetic traits to adapt to the new environment.

However, when the environment changes at a faster pace than evolution can produce new traits, species that already have the physiological and behavioural abilities within its genetic code to cope with the changes will have an advantage.

A bee species that can already access more than one food source (such as the honey bee) can quickly adapt to changing plant communities and survive when other specialist species cannot.

‘Beehaving’ differently in the heat

Bee species that can alter their behaviour to cope with high temperatures (for example by changing their activity periods to avoid the hottest part of the day) will tolerate climate stress. But these adaptive capabilities have their limits.

Increasing heat waves can directly kill bees by overheating them and/or melting wax-based nesting structures. Drought can also kill bees indirectly, by causing dehydration or starvation through the death of food plants.

Alternatively, it is possible that bees will change their range in response to changing climactic zones. As one area gets too hot, the bees can move to more tolerable climatic conditions.

However, a study on bumble bees conducted in North America and Europe using data spanning the last century indicate that bumble bees do not move in a way that “tracks” warming. Rather, they stay in the same place despite the changing climate.

A socially flexible sweat bee can switch behaviour depending on the environmental conditions
Patty O’Hearn Kickham/flickr, CC BY-ND

While most of us think bees live in colonies, most of the world’s bees are actually solitary. In solitary species, female bees generally live alone in nests they’ve built, in which they raise their offspring.

Most bee species are also fixed in their social structures, with some species living alone while others have varying degrees of social behaviour. However, a few native bee can change their social structure depending on the environment, so bees that are solitary in one set of environmental conditions are social under another. These socially flexible species may have surprising responses to climate change.

As the weather warms and growing seasons lengthen, socially flexible bees (such as some carpenter and sweat bees) may, eventually, switch permanently from solitary behaviour to social behaviour. However this may also decrease their ability to adapt.

Leaving wildflower borders at the edge of fields can provide habitat for bees
ukgardenphotos/flickr, CC BY-ND

Bee habitats are disappearing

While changing the climate, humans have also made dramatic changes to Earth’s landscapes. Increasing human population and our consequent demands for space to live and grow food has meant that more of the bees’ habitat has been changed into urban and intensive agricultural areas.

This has resulted in loss of habitat and food sources for the bees (as well as exposure to potentially harmful pesticides). Large areas of monoculture crops fragment vital bee habitats that are required for native bee food and nests. The crops may not provide a suitable food sources for certain bee species and generalist bee species such as the honey bee suffer compromised immunity when only fed one source of pollen.

Our agricultural pollination needs cannot be met with honey bee pollination alone, as native bees are often specialised pollinators for crops honey bees cannot pollinate. For example, the solitary alfalfa leafcutting bee pollinates alfalfa, an important crop for animal feed and a plant with a trip-mechanism that honey bees avoid. Furthermore, native and honey bees can work cooperatively to pollinate, producing the maximum crop yield required for efficient food production.

The problems with taking over bee habitats can be partly resolved by leaving adequate wildflower borders between fields and in urban areas. This can link habitats and food sources (such as Norway’s bee highway) so that bees can move across the entire landscape.

Bees are interpretive dancers

Just as plants and bees are codependent, we are dependent on their relationship for survival and must do our best to keep bees healthy, and this means more research about all aspects of the lives of wild bees including their influence on pollination. Without knowledge of how they live and their habitat needs, we cannot adequately protect them.

Honey bees preform waggle dances to tell the rest of the hive where the best flowers are

In the case of the honey bee, we can find out what food sources it prefers by asking the bees themselves. Honey bees perform a waggle dance to communicate the direction and distance of their preferred food source, and how much they like it (a honey bee dance is more “vigorous” when they really value a food source).

By interpreting the dance of the honey bee workers, and identifying the pollen on their legs to determine which plant they are dancing about, we can find out where and when they like to forage. This information on foraging behaviour can also be used as an indicator of the biodiversity in the area, and whether the landscape is healthy for bees.

The knowledge we gain from the bees can be used to help conserve them, and in turn, conserve ourselves.

The Conversation

Marianne Peso is Lecturer/Postdoctoral Research Associate at Macquarie University.

This article was originally published on The Conversation.
Read the original article.