Flies like yellow, bees like blue: how flower colours cater to the taste of pollinating insects


Hoverfly (Eristalis tenax) feeding on marigold.
Fir0002/Flagstaffotos, CC BY-NC

Jair Garcia, RMIT University; Adrian Dyer, RMIT University, and Mani Shrestha, Bayreuth UniversityWe all know the birds and the bees are important for pollination, and we often notice them in gardens and parks. But what about flies?

Flies are the second most common type of pollinator, so perhaps we should all be taught about the bees, the flies and then the birds. While we know animals may see colour differently, little was known about how fly pollination shapes the types of flowers we can find in nature.

In our new study we address this gap in our knowledge by evaluating how important fly pollinators sense and use colour, and how fly pollinated flowers have evolved colour signals.

Specialed flower visiting flies: a hoverfly (Eristalis tenax) (left panel), and a bee-fly (Poecilanthrax apache) (right panel)
Michael Becker, Pdeley

The way we see influences what we choose

We know that different humans often have preferences for certain colours, and in a similar way bees prefer blue hues.

Our colleague Lea Hannah has observed that hoverflies (Eristalis tenax) are much better at distinguishing between different shades of yellow than between different blues. Other research has also reported hoverflies have innate responses to yellow colours.




Read more:
The mystery of the blue flower: nature’s rare colour owes its existence to bee vision


Many flowering plants depend on attracting pollinators to reproduce, so the appearance of their flowers has evolved to cater to the preferences of the pollinators. We wanted to find out what this might mean for how different insects like bees or flies shape flower colours in a complex natural environment where both types of insect are present.

The Australian case study

Australia is a natural laboratory for understanding flower evolution due to its geological isolation. On the mainland Australian continent, flowers have predominately evolved colours to suit animal pollination.

Around Australia there are plant communities with different pollinators. For example, Macquarie Island has no bees, and flies are the only animal pollinator.

We assembled data from different locations, including a native habitat in mainland Australia where both bees and flies forage, to model how different insects influence flower colour signal evolution.

Measuring flower colours

Since we know different animals sense colour in different ways, we recorded the spectrum of different wavelengths of light reflected from the flowers with a spectrometer. We subsequently modelled these spectral signatures of plant flowers considering animal perception, allowing us to objectively quantify how signals have evolved. These analyses included mapping the evolutionary ancestry of the plants.

Generalisation or specialisation?

According to one school of thought, flower evolution is driven by competition between flowering plants. In this scenario, different species might have very different colours from one another, to increase their chances of being reliably identified and pollinated. This is a bit like how exclusive brands seek customers by having readily identifiable branding.

An alternative hypothesis to competition is facilitation. Plants may share preferred colour signals to attract a higher number of specific insects. This explanation is like how some competing businesses can do better by being physically close together to attract many customers.




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


Our results demonstrate how flower colour signalling has dynamically evolved depending on the availability of insect pollinators, as happens in marketplaces.

In Victoria, flowers have converged to evolve colour signals preferred by their pollinators. The flowers of fly-pollinated orchids are typically yellowish-green, while closely related orchids pollinated by bees have more bluish and purple colours. The flowers appeared to share the preferred colours of their main pollinator, consistent with a facilitation hypothesis.

Typical flowers preferred by bees (Lobelia rhombifolia, left panel) and flies (Pterostylis melagramma, right panel) encountered in our study sites. Inserts show the spectral profile for each species as measured by a spectrometer.
Mani Shrestha

Our research showed flies can see differences between flowers of different species in response to the pollinator local “market”.

On Macquarie Island, where flies are the only pollinators, flower colours diverge from each other – but still stay within the range of the flies’ preferred colours. This is consistent with a competition strategy, where differences between plant species allow flies to more easily identify the colour of recently visited flowers.

When both fly and bee pollinators are present, flowers pollinated by flies appear to “filter out” bees to reduce the number of ineffective and opportunistic visitors. For example, in the Himalayas specialised plants require flies with long tongues to access floral rewards. This is similar to when a store wants to exclusively attract customers specifically interested in their product range.

Our findings on fly colour vision, along with novel precision agriculture techniques, can help using flies as alternative pollinators of crops. It also allows us to understand that if we want to see a full range of pollinating insects including beautiful hoverflies in our parks and gardens, we need to plant a range of flower types and colours.The Conversation

Jair Garcia, Research fellow, RMIT University; Adrian Dyer, Associate Professor, RMIT University, and Mani Shrestha, Postdoc & International Fellow, Disturbance Ecology, Bayreuth University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

How a bee sees: tiny bumps on flower petals give them their intense colour — and help them survive


Scarlett Howard, Author provided

Adrian Dyer, RMIT University and Jair Garcia, RMIT UniversityThe intense colours of flowers have inspired us for centuries. They are celebrated through poems and songs praising the red of roses and blue of violets, and have inspired iconic pieces of art such as Vincent Van Gogh’s sunflowers.

Vase with Three Sunflowers by Vincent Van Gough
Vase with Three Sunflowers by Vincent Van Gogh.

But flowers did not evolve their colour for our pleasure. They did so to attract pollinators. Therefore, to understand why flowers produce such vibrant colours, we have to consider how pollinators such as bees perceive colour.

When observed under a powerful microscope, most flower petals show a textured surface made up of crests or “bumps”. Our research, published in the Journal of Pollination Ecology, shows that these structures have frequently evolved to interact with light, to enhance the colour produced by the pigments under the textured surface.

A flower of Tibouchina urvilleana observed under a powerful scanning electron microscope shows a typical bumpy petal surface (left). In comparison, the opposite (abaxial) petal side, rarely seen by an approaching pollinator, shows a less textured surface (right).
Author provided

Sunshiney daze

Bees such as honeybees and bumblebees can perceive flower colours that are invisible to us — such as those produced by reflected ultraviolet radiation.

Plants must invest in producing reliable and noticeable colours to stand out among other plant species. Flowers that do this have a better chance of being visited by bees and pollinating successfully.

However, one problem with flower colours is sunlight may directly reflect off a petal’s surface. This can potentially reduce the quality of the pigment colour, depending on the viewing angle.

You may have experienced this when looking at a smooth coloured surface on a sunny day, where the intensity of the colour is affected by the direction of light striking the surface. We can solve this problem by changing our viewing position, or by taking the object to a more suitable place. Bees, on the other hand, have to view flowers in the place they bloom.

Bumblebee on a smooth blue surface, where the colour is affected by light reflection.

We were interested in whether this visual problem also existed for bees, and if plants have evolved special tricks to help bees find them more easily.




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How bees use flower surfaces

It has been known for some time that flowering plants most often have conical-shaped cell structures within the texture of their petal surfaces, and that flat petal surfaces are relatively rare. A single plant gene can manipulate whether a flower has conical-shaped cells within the surface of a petal — but the reason why this evolved has remained unclear.

Past research suggested the conical petal surface acted as a signal to attract pollinators. But experiments with bees have shown this isn’t the case. Other explanations relate to hydrophobicity (the ability to repel water). But again, experiments have revealed this can’t be the only reason.

We investigated how bumblebees use flower surfaces with or without conical petal shapes. Bees are a useful animal for research as they can be trained to collect a reward, and tested to see how they perceive their environment.

Bumblebees can also be housed and tested indoors, where it is easier to precisely mimic a complex flower environment as it might work in nature.

Flowers cater to a bee’s needs

Our colleague in Germany, Saskia Wilmsen, first measured the petal surfaces of a large number of plants and identified the most common conical surfaces.

She then selected some relatively smooth petal or leaf surfaces reflecting light from an artificial source as a comparison. Finally, blue casts were made from these samples, and subsequently displayed to free-flying bees.

In the experiment, conducted with bumblebees in Germany, a sugar solution reward could be collected by bees flying to any of the artificial flowers. They had to choose between flying either towards “sunlight” — which could result in light reflections affecting the flower’s coloration — or with the light source behind the bee.

The experiment found when light came from behind the bees, there was no preference for flower type. But for bees flying towards the light, there was a significant preference for choosing the flower with a more “bumpy” conical surface. This bumpy surface served to diffuse the incoming light, improving the colour signal of the flower.

The results indicate flowers most likely evolved bumpy surfaces to minimise light reflections, and maintain the colour saturation and intensity needed to entice pollinators. Humans are probably just lucky beneficiaries of this solution biology has evolved. We also get to see intense flower colours. And for that, we have pollinators to thank.




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


The Conversation


Adrian Dyer, Associate Professor, RMIT University and Jair Garcia, Research fellow, RMIT University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

A lone tree makes it easier for birds and bees to navigate farmland, like a stepping stone between habitats


Shutterstock

Carla Archibald, Deakin University; Eduardo van den Berg, Federal University of Lavras, and Jonathan Rhodes, The University of QueenslandVast, treeless paddocks and fields can be dangerous for wildlife, who encounter them as “roadblocks” between natural areas nearby. But our new research found even one lone tree in an otherwise empty paddock can make a huge difference to an animal’s movement.

We focused on the Atlantic Forest in Brazil, a biodiversity hotspot with 1,361 different known species of wildlife, such as jaguars, sloths, tamarins and toucans. Habitat loss from expanding and intensifying farmland, however, increasingly threatens the forest’s rich diversity of species and ecosystems.

We researched the value of paddock trees and hedges for birds and bees, and found small habitat features like these can double how easily they find their way through farmland.

This is important because enabling wildlife to journey across farmlands not only benefits the conservation of species, but also people. It means bees can improve crop pollination, and seed-dispersing birds can help restore ecosystems.

Connecting habitats

Lone trees in paddocks, hedges and tree-lined fences are common features of farmlands across the world, from Brazil to Australia.

They may be few and far between, but this scattered vegetation makes important areas of refuge for birds and bees, acting like roads or stepping stones to larger natural habitats nearby.

Scattered paddock trees, for instance, offer shelter, food, and places to land. They’ve also been found to create cooler areas within their canopy and right beneath it, providing some relief on scorching summer days.

Hedges and tree-lined fences are also important, as they provide a safe pathway by providing hiding places from predators.

White-browed meadowlark perched on a bush in a farm paddock within the Atlantic Forest
White-browed meadowlark perched on a bush in a farm paddock within the Atlantic Forest.
Milton Andrade Jr, CC BY

For our research, we used satellite images of the Atlantic Forest and randomly selected 20 landscapes containing different amounts of forest cover.

We then used mathematical models to calculate the habitat connectivity of these landscapes for three groups of species — bees, small birds such as the rufous-bellied thrush, and large birds such as toucans — based on how far they can travel.




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And we found in areas with low forest cover, wildlife is twice as likely to move from one natural habitat to another if paddock trees and hedges can be used as stepping stones.

We also found vegetation around creeks and waterways are the most prevalent and important type of on-farm habitat for wildlife movement. In Brazil, there are legal protections for these areas preventing them from being cleared, which means vegetation along waterways has become relatively common compared to lone trees and hedges, in places with lower forest cover.

Insights for Australia

While the contribution of lone trees, hedges and tree-lined fences towards conservation targets is relatively low, our research shows they’re still important. And we can apply this knowledge more widely.

Two koalas sitting on a branch
Koalas use roadside vegetation for feeding and resting.
Shutterstock

For example, in Australia, many koala populations depend on scattered trees for movement and habitat. In 2018, CSIRO researchers in Queensland tracked koalas using GPS, and found koalas used roadside vegetation and scattered trees for feeding and resting significantly more than they expected.

Likewise, lone trees, hedges and tree-lined fences can also facilitate the movement of Australian fruit-eating birds such as the olive-backed oriole and the rose-crowned fruit dove. Improving habitat connectivity can help these birds travel across landscapes, feeding and dispersing seeds as they go.

In fragmented landscapes, where larger patches of vegetation are hard to find, dispersing the seeds of native plants encourages natural regeneration of ecosystems. This is a key strategy to help achieve environmental restoration and conservation targets.

Policies overlook lone trees

In Brazil, there’s a strong initiative to restore natural areas, known as the Brazilian Pact for Restoration. This pact is a commitment from non-government organisations, government, companies and research centres to restore 15 million hectares of native vegetation by 2050.

However, the pact doesn’t recognise the value of lone trees, hedges and tree-lined fences.




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Likewise, the Brazilian Forest Code has historically provided strong legal protection for forests since it was introduced. While this policy does value vegetation along waterways, it overlooks the value of lone trees, hedges or tree-lined fences.

These oversights could result in poor connectivity between natural areas, seriously hampering conservation efforts.

Australia doesn’t fare much better. For example, in Queensland, the native vegetation management laws protect only intact native vegetation or vegetation of a certain age. This means scattered, but vital, vegetation isn’t protected from land clearing.

Small habitat features scattered across a farm paddock in the Atlantic Forest.
Flávia Freire Siqueira, CC BY., Author provided

Helping your local wildlife

But farmers and other landowners in Australia can make a big difference through land stewardship grant schemes (such as from Landcare) and private land conservation programs (such as Land for Wildlife or conservation covenants).

These schemes and programs can help landowners finance revegetation and protect native vegetation. Grants and programs vary by state and territory, and local council.




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Restoring natural areas is a key goal on the global conservation agenda for the next decade, and it’s clear that lone trees, hedges and tree-lined fences on farms may play a larger role than once thought.

So think twice before you remove a tree or a hedge. It might be a crucial stepping stone for your local birds and bees.


The authors gratefully acknowledge the contributions of Dr Flávia Freire Siqueira who led this research collaboration, and co-authours Dr Dulcineia de Carvalho and Dr Vanessa Leite Rezende from the Federal University of Lavras.The Conversation

Carla Archibald, Research Fellow, Conservation Science, Deakin University; Eduardo van den Berg, , Federal University of Lavras, and Jonathan Rhodes, Associate Professor, The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Phantom of the forest: after 100 years in hiding, I rediscovered the rare cloaked bee in Australia


James B. Dorey, Flinders University

It’s not often you get to cast your eyes on a creature feared to be long-gone.

Perhaps that’s why my recent rediscovery of the native bee species Pharohylaeus lactiferus is so exciting — especially after it spent a century eluding researchers.

But how did it stay out of sight for so long?

A creature overshadowed

Australia is home to 1654 named species of native bee. Unfortunately, these are often overshadowed in the eyes of public by the widespread and invasive European honeybee.

Scientific research on Australian native bees is lagging, compared to many other nations.

With this in mind, it may not be surprising to learn some native species can go unnoticed for many years. Although, when it’s the only representative of a whole genus, one might start to worry about losing something special.

In this case the genus is Pharohylaeus, where “pharo” means “cloaked”, as these bees’ first three abdominal segments overlay the others to resemble a cloak.

I found the cloaked bee P. lactiferus during a major east coast sampling effort of more than 225 unique sites. The discovery, and what I learnt from it, helped me find more specimens at two additional sites.

It also made me wonder why P. lactiferus had been missing for so long. Is it naturally rare, hard to find, or perhaps threatened?




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Taxonomic trouble

Many Australian bees are very difficult to identify to a species level. In fact, some might be nearly impossible.

However, P. lactiferus is a relatively distinct black and white masked bee. Masked bees are those from the subfamily Hylaeinae, named so because they often have striking, bright facial patterns on an otherwise dark face.

With this distinctive appearance, identification issues weren’t a contributor to the mystery of P. lactiferus.

Seeing red

Still, despite having sampled extensively across sites and flowering plant species, I only found P. lactiferus on two types of plant: the firewheel tree and the Illawarra flame tree — both of which boast exuberant red flowers.

_Brachychiton acerifolius_ flowers.
The Illawarra flame tree (Brachychiton acerifolius).
James Dorey, Author provided

Bees generally don’t see shades of red, so such plants are usually pollinated by birds. It could be that bee researchers tend to avoid sampling these red flowering plant species for this reason.

Then again, bee vision and bee perception are not always the same. And bees are also guided by their keen sense of smell.

Habitat specialisation

So far, I’ve only found P. lactiferus within about 200 metres of one major vegetation subgroup, which is tropical or sub-tropical rainforest.

The first specimens I collected were in Atherton, Queensland. I later found more in Kuranda and Eungella. Some of these specimens are now stored in the South Australian Museum.

The habitat specialisation of P. lactiferus may suggest it has an above-average level of vulnerability to disturbances, particularly if it needs a strict set of requirements to make it through its entire life-cycle.

It is one of myriad bee species that nest in narrow, wooden hollows. Some bees such as Amphylaeus morosus dig these themselves and may require specific plant species to make their nest in.

Others such as Exoneurella tridentata need to use holes made by weevil larvae in two particular tree species: western myall and bullock bush.

Rainforests are also notoriously hard to sample. If a bee species spends much of its time in the high canopy, finding it would be difficult.

That said, two early collectors managed to find six specimens of P. lactiferus between 1900 and 1923. So its rarity doesn’t necessarily come down to it being a canopy-dweller.




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Potential threats

We know in the bioregions where P. lactiferus has been found that rainforests have undergone both habitat destruction and fragmentation since European colonisation. This threat hasn’t abated and Queensland is still a land-clearing hotspot.

We also know these rainforests burnt across Queensland every year between 1988 and 2016. The 2019-20 black summer megafires burnt nearly double the area of any previous year.

For some bee species this may not be a problem. But for a species that potentially requires specific foods, habitats and even other species, it could mean local extinction.

Only so many populations of a single species can disappear, before there are none left.

Where does this leave us?

P. lactiferus persists, which is wonderful. Unfortunately, we can’t yet say whether or not it is threatened.

To determine this confidently would require a robust, extensive and targeted survey regime.

We may not be able to undertake such a regime for all 1654 of the named bee species in Australia. But perhaps we could make that effort for the country’s only cloaked bee.The Conversation

James B. Dorey, PhD Candidate, Flinders University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The mystery of the blue flower: nature’s rare colour owes its existence to bee vision



Shutterstock

Adrian Dyer, RMIT University

At a dinner party, or in the schoolyard, the question of favourite colour frequently results in an answer of “blue”. Why is it that humans are so fond of blue? And why does it seem to be so rare in the world of plants and animals?

We studied these questions and concluded blue pigment is rare at least in part because it’s often difficult for plants to produce. They may only have evolved to do so when it brings them a real benefit: specifically, attracting bees or other pollinating insects.

We also discovered that the scarcity of blue flowers is partly due to the limits of our own eyes. From a bee’s perspective, attractive bluish flowers are much more common.

A history of fascination

The gold and blue funerary mask of the ancient Egyptian pharaoh Tutankhamun.
The ancient mask of the pharaoh Tutankhamun is decorated with lapis lazuli and turquoise.
Roland Unger / Wikimedia, CC BY-SA

The ancient Egyptians were fascinated with blue flowers such as the blue lotus, and went to great trouble to decorate objects in blue. They used an entrancing synthetic pigment (now known as Egyptian blue) to colour vases and jewellery, and semi-precious blue gemstones such as lapis lazuli and turquoise to decorate important artefacts including the Mask of Tutankhamun.




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Blue dye for fabric is now common, but its roots lie in ancient Peru, where an indigoid dye was used to colour cotton fabric about 6000 years ago. Indigo blue dyes reached Europe from India in the 16th century, and the dyes and the plants that produced them became important commodities. Their influence on human fashion and culture are still felt today, perhaps most obviously in blue jeans and shirts.

Renaissance painters in Europe used ground lapis lazuli to produce dazzling works that captivated audiences.

A painting of a woman in a vivid blue robe and white hood, with bowed head and clasped hands.
The Virgin in Prayer by the Italian painter Sassoferrato, circa 1650, highlights the vivid blue colour made with ground lapis lazuli.

Today many blues are created with modern synthetic pigments or optical effects. The famous blue/gold dress photograph that went viral in 2015 not only shows that blue can still fascinate — it also highlights that colour is just as much a product of our perception as it is of certain wavelengths of light.

Why do humans like blue so much?

Colour preferences in humans are often influenced by important environmental factors in our lives. An ecological explanation for humans’ common preference for blue is that it is the colour of clear sky and bodies of clean water, which are signs of good conditions. Besides the sky and water, blue is relatively rare in nature.

What about blue flowers?

We used a new online plant database to survey the the relative frequencies of blue flowers compared to other colours.

Among flowers which are pollinated without the intervention of bees or other insects (known as abiotic pollination), none were blue.

But when we looked at flowers that need to attract bees and other insects to move their pollen around, we started to see some blue.

This shows blue flowers evolved for enabling efficient pollination. Even then, blue flowers remain relatively rare, which suggests it is difficult for plants to produce such colours and may be a valuable marker of plant-pollinator fitness in an environment.

Global flower colour frequency for human visual perception (A) shows when considering animal pollinated species less than 10% are blue (B), and for wind pollinated flowers almost none are observed to be blue (C).
Dyer et al., Author provided

We perceive colour due to how our eyes and brain work. Our visual system typically has three types of cone photoreceptors that each capture light of different wavelengths (red, green and blue) from the visible spectrum. Our brains then compare information from these receptors to create a perception of colour.

For the flowers pollinated by insects, especially bees, it is interesting to consider that they have different colour vision to humans.




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Bees have photoreceptors that are sensitive to ultraviolet, blue and green wavelengths, and they also show a preference for “bluish” colours. The reason why bees have a preference for bluish flowers remains an open field of research.

Various blue flowers from our study.

Why understanding blue flowers is important

About one-third of our food depends on insect pollination. However, world populations of bees and other insects are in decline, potentially due to climate change, habitat fragmentation, agricultural practices and other human-caused factors.

The capacity of flowering plants to produce blue colours is linked to land use intensity including human-induced factors like artificial fertilisation, grazing, and mowing that reduce the frequency of blue flowers. In contrast, more stressful environments appear to have relatively more blue floral colours to provide resilience.

For example, despite the apparent rarity of blue flower colours in nature, we observed that in harsh conditions such as in the mountains of the Himalaya, blue flowers were more common than expected. This shows that in tough environments plants may have to invest a lot to attract the few available and essential bee pollinators. Blue flowers thus appear to exist to best advertise to bee pollinators when competition for pollination services is high.

Knowing more about blue flowers helps protect bees

Urban environments are also important habitats for pollinating insects including bees. Having bee friendly gardens with flowers, including blue flowers that both we and bees really appreciate, is a convenient, pleasurable and potentially important contribution to enabling a sustainable future. Basically, plant and maintain a good variety of flowers, and the pollinating insects will come.




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The Conversation


Adrian Dyer, Associate Professor, RMIT University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

‘Jewel of nature’: scientists fight to save a glittering green bee after the summer fires



Remko Leijs, Author provided

Katja Hogendoorn, University of Adelaide; Remko Leijs, Flinders University, and Richard V Glatz, University of Adelaide

This article is a preview of Flora, Fauna, Fire, a multimedia project launching on Monday July 13. The project tracks the recovery of Australia’s native plants and animals after last summer’s bushfire tragedy. Sign up to The Conversation’s newsletter for updates.


The green carpenter bee (Xylocopa aerata) is an iconic, beautiful native species described as a “jewel of nature” for its metallic green and gold colouring. Carpenter bees are so named because they excavate their own nests in wood, as opposed to using existing holes.

With a body length of about 2 centimetres, it is among the largest native bees in southern Australia. While not used in honey farming, it is an important pollinator for several species of Australian native plants.

Last summer’s catastrophic bushfires significantly increased the risk of local extinctions of this magnificent species. We have studied the green carpenter bee for decades. For example, after the 2007 fires on Kangaroo Island, we bolstered the remaining population by providing nesting materials.

To see our efforts – and more importantly, most of the habitat these bees rely on – destroyed by the 2020 fire was utterly devastating.

Much of Kangaroo Island was incinerated by the summer bushfires.
Daniel Mariuz/AAP

A crucial pollinator on the brink

The green carpenter bee is a buzz-pollinating species. Buzz pollinators are specialist bees that vibrate the pollen out of the flowers of buzz-pollinated plants.

Many native plants, such as guinea flowers, velvet bushes, Senna, fringe, chocolate and flax lilies, rely completely on buzz-pollinating bees for seed production. Introduced honey bees do not pollinate these plants.




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The green carpenter bee went extinct on mainland South Australia in 1906 and in Victoria in 1938. It still occurs on the relatively uncleared western half of Kangaroo Island in South Australia, in conservation areas around Sydney, and in the Great Dividing Range in New South Wales.

Local extinctions were probably due to habitat clearing and large, intense bushfires. The last time the green carpenter bee was seen in Victoria was early December 1938 in the Grampians, which burnt completely during the Black Friday fires of January 1939.

There are several reasons green carpenter bees are vulnerable to fire, including:

  • the species uses dead wood for nesting, which burns easily
  • if the nest burns before the offspring matures in late summer, the adult female might fly away but won’t live long enough to reproduce again, and
  • the bees need floral resources throughout the year.
A male green carpenter bee.
Remko Leijs, Author provided

Nowhere to nest

The bees mainly dig their nests in two types of soft wood: dry flowering stalks of grass trees and, crucially important, large dead Banksia trunks. The availability of both nesting materials is intricately connected with fire.

Green carpenter bees sometimes nest n the dried flowering stalks of grass trees, also known as Xanthorrhoea.
Remko Leijs, Author provided

Grass trees flower prolifically after fire, but the dry stalks are only abundant between two and five years after fire. Banksia species don’t survive fire, and need to grow for at least 30 years to become large enough for the bees to use.

Bees nesting in an artificial stalk.
Remko Leijs, Author provided

With increasingly frequent and intense fires, there’s not enough time for Banksia trunks to grow big enough, before they’re wiped out by the next fire.

A helping hand after the 2007 fires

In 2007, Flinders Chase National Park on Kangaroo Island burnt almost entirely.

An artificial stalk nesting site installed in a Xanthorrea.
Remko Leijs, Author provided

However, in long-unburnt areas adjacent to the park, carpenter bee nests were still present. From there, they colonised the many dry grass tree stalks that resulted from the fire in the park.

In 2012, most flowering stalks had decayed. In an attempt to bolster population size, we successfully developed artificial nesting stalks to tide the bees over until new Banksia, suitable for nesting, would become available.

Since then, each year we’ve placed artificial nesting stalks in fire-affected areas where the bee still occurred. Almost 300 female carpenter bees have successfully used our stalks to raise their offspring.

Then came the January 2020 fires

At the time of the 2020 fires on Kangaroo Island, there were more than 150 nests containing mature brood in the stalks we had provided.

We’d placed these in 12 sites in and around Flinders Chase National Park, to spread risk – to no avail, as they all burnt.

We were horrified to see the intensity and speed of the fire that turned our efforts to ash, along with most of the remnant, long (more than 60 years) unburnt Banksia habitat the bees rely on. In New South Wales, much of the species’ natural range was also burnt.

The yellow dots represent known green carpenter bee nests. In red: the area burnt in 2020. Only a subset of the remaining green and yellow patches still have the right vegetation for the green carpenter bee.
Nature Maps SA/Remko Leijs, Author provided

What’s next for the green carpenter bee?

To fully appreciate the impact, we need to survey the remaining long unburnt areas on Kangaroo Island and in NSW.

Encouragingly, we have already found a few natural nests on Kangaroo Island, but the remaining suitable areas are small and isolated, and densities are likely to be low.

With funds raised through the Australian Entomological Society and the Wheen Bee Foundation, and with help of the Kingscote Men’s Shed, we are making new nesting stalks.

The Kingscote Men’s Shed on Kangaroo Island is helping build new nesting stalks.
Remko Leijs, Author provided

With permission of landholders, we’ll place these new stalks in areas with good floral support, to enhance reproduction and help the bees disperse into conservation areas once suitable.

As we have learnt, success is not guaranteed. Extensive and repeated bush fires, combined with asset protection and fuel reduction burns, are making longtime unburnt habitat increasingly rare. It is this lack of old, continuous, unburnt forest that severely threatens the green carpenter bees’ existence.

The future of fire-vulnerable biodiversity

The carpenter bee is not the only species facing this problem. Many Australian plants and animals are not resilient to high frequency fires, no matter their intensity or time of year.

The ecological importance of longtime unburnt forest needs urgent recognition, as increased fire frequency – both of natural and “managed” fires – is likely to drive a suite of species to extinction.

For Kangaroo Island, this could include several small mammals, glossy black cockatoos, and a range of invertebrate species, including the green carpenter bees.

Given the expected increase in fire frequency and intensity associated with global heating, it’s time we recognise fire-vulnerable species as a category that requires urgent habitat protection.




Read more:
After last summer’s fires, the bell tolls for Australia’s endangered mountain bells


The Conversation


Katja Hogendoorn, University of Adelaide; Remko Leijs, Researcher, Flinders University, and Richard V Glatz, Associate research scientist, University of Adelaide

This article is republished from The Conversation under a Creative Commons license. Read the original article.

One, then some: how to count like a bee


Scarlett Howard, Deakin University and Adrian Dyer, RMIT University

If you were a honeybee, how would you choose where to find flowers? Imagine your first flight out of the hive searching for food. What would you do if you saw flower patches with one flower, or three, or twelve, or twenty?

Our new study, published in the Journal of Experimental Biology, tested honeybees on exactly this question. We wanted to understand how honeybees choose where to forage in environments like greenhouses where our food is pollinated, in local parks, or in our own backyards.

Specifically, our research looked at whether honeybees with no specific numerical training could choose a flower patch based on the quantity of flowers it had.

We found the bees could tell the difference between groups of 1 vs 4 flowers – but not between, say, 4 vs 5. Basically, they couldn’t differentiate between groups of 2 or more flowers.

A honeybee pollinating a strawberry plant flower in a greenhouse.
Adrian Dyer/RMIT University

A mathematical matter of life and death

The ability to tell the difference between two quantities can mean life or death for an animal. “Quantity discrimination” can be vital for survival in tasks including:

  • resource comparison: choosing a larger quantity of food

  • aggressive interactions: choosing to avoid conflicts with larger groups of individuals, and

  • avoiding predators: choosing to stay with a larger group of animals of the same species to reduce your chance of being eaten.

We are gaining a better understanding of quantity discrimination across the animal kingdom. Primates and other mammals, amphibians, reptiles, birds and fish all display some form of quantity discrimination in day-to-day tasks. For example, fish use quantity discrimination to stay in larger groups to reduce the chance of being eaten by a predator.

However, little is known about spontaneous number choices by insects.




Read more:
We taught bees a simple number language – and they got it


How do bees choose where to forage?

Honeybees assess the available flowers based on several factors, including scent, colour, shape and size.

Backyard flowers; which patch to choose if you were a bee?
Adrian Dyer/RMIT University

Honeybees typically visit around 150 individual flowers per flight from the hive to collect resources such as nectar or pollen. For a honeybee, a high quantity of flowers in a single area would mean less energy exertion than having to fly to many flower patches with less flowers.

Using different numbers of artificial flowers, we wanted to test whether individual honeybees could discriminate between a range of quantities, and how they might determine the quality of a flower patch.

Our honeybees were shown pairs of flower quantities ranging from easier number comparisons (such as 1 flower vs 12 flowers) to more challenging scenarios (such as 4 flowers vs 5 flowers).

The experimental set-up (left) and the quantity comparisons (right). Honeybees succeeded at spontaneously discriminating between 1 vs 12, 1 vs 4, and 1 vs 3 flowers, but no other comparisons. The honeybees were trained to associate single yellow dots with sugar water before being shown quantity comparisons.
Scarlett Howard

Interestingly, despite previous findings that trained honeybees can discriminate between challenging quantities and can also learn to add and subtract, the bees performed poorly in our spontaneous number task.

We found they were only able to discriminate between 1 vs 3, 1 vs 4, and 1 vs 12 flowers – wherein they preferred the larger quantity. When 1 flower was an option they succeeded, but confused any comparisons between groups of 2 flowers or more.

This result suggests flower patch choice based on numerical-type cues is difficult for honeybees. And this has implications for how flower displays are interpreted.

A honeybee flies towards three flowers.
Scarlett Howard

With today being World Bee Day, why not take the opportunity to discover what bees are doing in gardens near you. Chances are they’re going to any flower patch with more than one flower, rather than paying much attention to absolute numbers.




Read more:
Bees learn better when they can explore. Humans might work the same way


The Conversation


Scarlett Howard, Postdoctoral research fellow, Deakin University and Adrian Dyer, Associate Professor, RMIT University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Aussie scientists need your help keeping track of bees (please)



The Asian honey bee (Apis cerana) has been found in Cairns. It’s just one of the introduced bees buzzing under the radar.
Tobias Smith, Author provided

Manu Saunders, University of New England; Callum McKercher, University of New England; Mark Hall, Western Sydney University; Tanya Latty, University of Sydney, and Tobias Smith, The University of Queensland

Bees get a lot of good press. They pollinate our crops and in some cases, make delicious honey. But bees around the world face serious threats, and the public can help protect them.

Of more than 20,400 known bee species in the world, about 1,650 are native to Australia. But not all bees found in Australia are native. A few species have been introduced: some on purpose and others secretly hitchhiking, usually through international trade routes.

As bee researchers, we’ve all experienced seeing a beautiful, fuzzy striped bee buzzing about our gardens, only to realise it’s an exotic species far from home.




Read more:
The farmer wants a hive: inside the world of renting bees


We need the public’s help to identify the bees in Australian backyards. There’s a good chance some are not native, but are unwanted exotic species. Identifying new intruders before they become established will help protect our native species.

The European honey bee (Apis mellifera) fuels a valuable honey industry and contributes to agricultural pollination. Other introduced species are far less welcome.
Tobias Smith

Exotic bees in Australia

The European honey bee (Apis mellifera) is the best-known introduced species, first brought to Australia in the early 1800s. It is now well-established throughout the country, with profitable industries built around managed populations.

Other invasive species in Australia are less well known (or loved). The European bumblebee (Bombus terrestris) is present in high numbers in Tasmania, but isn’t thought to be established on mainland Australia.

This bumblebee has caused major harm to native bees in South America, competing for resources and spreading disease.

In northern Queensland, the Asian honey bee (Apis cerana) is established around Cairns and Mareeba, from a single incursion in 2007. The original founding colony is thought to have been a stowaway on a boat that sailed to Cairns from somewhere in southeast Asia or the Pacific, where this bee is widespread.

New Asian honey bee incursions at Australian ports occur almost annually, most recently in Townsville and Melbourne. But swift biosecurity responses have so far stopped them becoming established.

The European bumble bee (Bombus terrestris) lives in large numbers in Tasmania, but is not established on the mainland.
Tobias Smith, Author provided

Why should we care?

Most insects can spread and establish breeding populations before anyone notices them, so it’s important we pay attention to these small intruders.

Introduced species can bring new parasites or diseases into the country that may harm native insects – including our stingless bees that are so vital to crop pollination – or affect the valuable European honey bee industry.

While bumblebees may help commercial pollination in a handful of Australian crops, they and other introduced species can also compete with native species for resources, or spread weeds.

Most resources go to monitoring invasive species with a more dramatic and understood effect on agriculture and the environment. Bees sneak under the radar – but we’re still curious.

Take the African carder bee (Pseudoanthidium repetitum), which arrived in Australia in the early 2000s. Thanks to citizen scientists, we know they are spreading rapidly. In 2014, they were the third most common bee species found in a survey of Sydney community gardens.

An African carder bee spotted in Lismore. They are the third most common bee species in Sydney community gardens.
Tobias Smith, Author provided

Just recently, we found two invasive African carder bees in a backyard in Armidale in northern New South Wales while testing out a new insect monitoring method. There are no confirmed records of this invasive bee in Armidale, although we have seen a few around town since 2017.




Read more:
Bees: how important are they and what would happen if they went extinct?


Although it’s usually exciting to find a new record for a native species, finding an exotic bee where it’s not supposed to be is worrying. How long have they been there, and how many others are there?

The European bumble bee was recently sighted to global biodiversity.

You don’t have to be totally sure what kind of bee you’ve spotted. Just snap some pictures and upload it to a citizen scientist app like iNaturalist with the date and location.
Jean and Fred/Flickr, CC BY

Will you help us keep track?

Anyone can help keep track of potential new invasive species, simply by learning more about the insects in your local area and sharing observations on citizen science platforms such as iNaturalist, or through targeted projects like the African carder bee monitoring project.

You don’t need to be sure exactly what species you’ve seen. Uploading some clear, high-resolution photos, along with the date and location of your observation, will help naturalists and researchers identify it.




Read more:
Wasps, aphids and ants: the other honey makers


You can also participate in events such as the twice-yearly Wild Pollinator Count or local Bioblitzes.

Your efforts can help us detect emerging threats, and add to our records of both native and non-native bees (and other species). Plus it’s a great excuse to get outdoors and learn more about the insect life in your area.


This article was co-written with Karen Retra.The Conversation

Manu Saunders, Research fellow, University of New England; Callum McKercher, PhD Student, University of New England; Mark Hall, Research fellow, Western Sydney University; Tanya Latty, Associate professor, University of Sydney, and Tobias Smith, Ecologist, bee researcher and stingless bee keeper, The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.