Wider benefits

We’ve gained a lot from connections with Sweden. Think Carl Linnaeus, Abba, Fika, Henning Mankell, Ikea, and Spotify, to name but a few, and you get the picture.  We could perhaps add to that list a UK pollinator project with an interesting Swedish connection. The work to reintroduce Bombus subterraneus – the Short-haired bumblebee – to these shores has certainly brought wider benefits than perhaps initially envisaged.

Short-haired bumblebee (c) Bumblebee Conservation Trust

That great bee observer Frederik Sladen noted the Short-haired bumblebee in 1912 as being common in the east and south of England, but over time even that concentrated hold loosened. It was last seen Britain in 1988, and twelve years later it was declared extinct on these shores.

Why had it disappeared?  The loss of so many of our wildflower meadows hit B. subterraneus especially hard. Here was a bee which thrived on a diet of kidney vetch, red clover and knapweed. The significant reduction in the availability of these food sources proved disastrous. 

Brown-banded carder worker in a wild flower meadow (c) Bumblebee Conservation Trust

It wasn’t always thus. Britain used to have loads of hay meadows – an estimated 7 million hectares around 100 years ago. Yet by the end of the 20th century it was reckoned we had lost an eye-watering 97 per cent of our wildflower meadows, which for nature was pretty catastrophic. Lose great swathes of habitat crammed with flowers and by extension you are going to lose great numbers of bees which relied on this source of food. 

A ray of hope emerged soon after the 2000 extinction announcement. As the world of reintroductions evolved there appeared to be an opportunity to reverse that loss. The Short-haired bumblebee fell under the reintroduction spotlight and thus began a story with an unexpected geographic twist.

The short-haired bumblebee project10th anniversary gathering with volunteers and project partners. (c) Bumblebee Conservation Trust

It was recalled that farmers in New Zealand had, around the end of the 19^th century,  imported bumblebees from the UK.  Puzzled that red clover, an important fodder crop, wasn’t setting seed, one enterprising entomologist aired his suspicion that it was the lack of bumblebee pollination that was the nub of the problem.  So a call went out to send bumblebee queens from England to New Zealand. Four species, including the Short-haired bumblebee, were despatched on refrigerated ships and soon adapted to life on the other side of the globe.

What if come the 21^st century that process was turned on its head and bees were sent in the other direction?  If the process was reversed, and queens brought back to England, could the Short-haired bumblebee perhaps be re-established in the UK?

However, those bumblebees in New Zealand were not the ideal solution initially imagined. DNA studies revealed genetic weakness in their population due to inbreeding (comparisons with museum samples held in the Natural History Museum bore this out) and this was compounded by a problematic six-month difference in seasons between the UK and New Zealand.

Undaunted, and fired by the hope reintroductions offered, the project to bring the Short-haired bumblebee back to these shores turned to Sweden. Not only did the Scandinavian nation have the bumblebee in question, but genetic studies revealed them to be a better match than their Antipodean counterparts.

Nevertheless, as many a weary conservationist will confirm, the waters don’t always run smoothly in the reintroduction world, particularly in the early stages. If you have followed beaver and sea eagle reintroductions you will know that the path can be littered with misunderstandings and spats. The prospect of 100 queen Short-haired bumbles being removed from the Skane province of Sweden soon created a mini-storm. There were fears in some quarters that this was unsanctioned and would threaten the bee in southern Sweden, and it took a series of meetings to allay public concerns that the project could herald the demise of this popular species.

As is so often the case it transpired too that a communication issue was afoot. The  project to remove the queens had indeed been vetted and approved.  With some relief the Swedish Board of Agriculture, Swedish Environmental Protection Agency, and the Swedish Threatened Species Unit, as well as the local County Administrative Board of Skane, were all confirmed as supportive.

Moss carder bumblebee (c) Bumblebee Conservation Trust

Nikki Gammans of Bumblebee Conservation Trust led the project aiming to ease the Short-haired bumblebee back into the UK.  Her story takes the reader back to 2009 when she devoted considerable energy to laying the groundwork for the reintroduction project. Firstly she diligently persuaded farmers in and around Dungeness in Kent of the merits of the project, and the role they could play in creating flowery-meadow habitat in advance of a release of bumblebees acquired in Sweden.

Mention of a specific site such as Dungeness perhaps makes this project sound rather narrow and local. In fact it was a project conducted at landscape scale, as it relied on building a network of farms supporting wildflower meadows. That connectivity was crucial if enough suitable habitat and forage was to be provided.  Management and maintenance methods which enhanced the prospects for flower-rich meadows were enthusiastically encouraged. Grazing regimes, field margins, cutting cycles, suitable seed mixes and rotation of stock were all employed in a way which would enable significant and effective habitat changes.

The groundwork laid, it was then a nervous time as, for five consecutive years, batches of Swedish queens were released in Kent. There was a disappointing initial failure in 2012, when it was reckoned a very wet summer did the damage. 

Ultimately Nikki’s project ran from 2009 to 2022 and is a remarkable testimony to her commitment and ability to work in partnership with a wide range of partners.  Thanks to her persuasive work with many farmers and other landowners, swathes of flower-rich habitat were established not only around Dungeness but across the Kent Marshes and beyond into East Sussex too.

Habitat green hay work party day with volunteers (c) Bumblebee Conservation Trust

The project has delivered considerable benefits for bumblebees generally. These range from an increase in other rare bumblebee species, through to landscape scale habitat improvements and the recruitment of over 65 volunteers committed to helping bumblebees. Nikki and her Bumblebee Conservation Trust colleagues continue to engage with the local community and between 2,000 and 3,000 people per year.  

Nikki is honest in her assessment of the reintroduction scheme. “Unfortunately, we don’t think the reintroduction has been successful,” she concedes, “For the years of release, we saw evidence of establishment but no confirmed sightings since they ended. We will continue to look though.

“Around 2,600 hectares of flower-rich meadows and 100 miles of B roads are to this day being actively managed to help the bumblebee. Other species have certainly taken advantage of the new habitat. Ruderal and Brown-banded carder bumblebees have increased as a result of the projects interventions, and the moss carder is stable where the project works but decreasing outside of this area.”

Bombus ruderatus (c) Bumblebee Conservation Trust

Not one to give in, Nikki still looks ahead with some optimism.  “From March 2022 we have been working on Bee Connected, the legacy project of the Short-haired bumblebee project. This project brings an increase in 40% of the project area extending further across Kent and into East Sussex. Our main aims are giving advice to farmers and other landowners, recruiting volunteers, conducting outreach such as identification days, and undertaking practical habitat management. We have a new 12 month trainee beginning in January and are currently recruiting a 24-month project officer.”

Britain is home to 24 species of bumblebee, and in addition we have over 250 species of other bee, mostly some quite small and easily overlooked.  In the wider world there are estimated to be around 20,000 species of bee.  Those numbers perhaps sound impressive but beneath them lies a story peppered with extinctions and declines.  Loss of habitat has hit our bees hard, the work of Nikki and her team in connection with the Short-haired bumblebee deserves our attention and advocates a strong focus on habitat restoration.

Further reading:

Nikki’s report on the project  

Chapter One of Dave Goulson’s highly readable ‘A Sting in the Tale’ delves into the background to short-haired bumblebees in New Zealand.

With sincere thanks to Nikki Gammans of Bumblebee Conservation Trust (project manager for Bee Connected) for all her help in the compilation of this article.

Bobby bright buttons

Some plants have delightful nicknames. Amongst them surely is devil’s-bit scabious, which enjoys the catchy alternative of Bobby Bright Buttons. A stalwart of many a meadow, this is a plant that captivates by looks as well as name.

Devil’s-bit scabious. ©Lorne Gill/SNH

Devil’s-bit scabious has an attractive flower head in a striking blue/purple colour.  It appeals to many species of butterfly and is also very popular with bees. It’s pretty robust, and you will easily find it between midsummer and early autumn (and later in the year in parts of southern England). It favours meadows and damp pastures.

Arguably one of its claims to fame is being the main foodplant for the marsh fritillary caterpillar. The marsh fritillary is giving cause for concern as numbers of this attractive butterfly sink dangerously low, so we should be grateful that devil’s-bit scabious is so robust. There is a lovely passage in Jane Smith’s beautifully illustrated homage to Oronsay, ‘Wild Island’, in which she talks about the joy of spending the first truly warm day of the year going out to look for the caterpillars of the marsh fritillary on devil’s-bit scabious.  Good news that that marsh fritillary features in Scotland’s Species on the Edge project.

Speaking of going outdoors looking at plants. If you feel the notion and fancy some fun then why not join in the Botanical Society of Britain & Ireland’s (BSBI) New Year plant hunt?  You would be helping them build a clearer picture of how our wild and naturalised plants are responding to changes in autumn and winter weather patterns. Their  twelfth New Year Plant Hunt will run from New Year’s Eve until Tuesday 3rd January 2023. You can find out more on their website.

Bumblebee feeding on devil’s bit scabious. ©Lorne Gill

This strikingly colourful devil’s-bit scabious is surely one of our easier flowers to identify. The round globe-shaped flower head sit exposed at the end of a stalk that can be up to half a metre tall and has so many tightly packed flowers that it is said by some to resemble a ‘busy’ pin-cushion (although I can’t actually remember the last time I laid eyes on a pin-cushion, and I suspect younger readers are frantically googling pin-cushion as we speak). You are unlikely to confuse it with any plant other than the field scabious which has pinker, paler flowers. I’m wary, however, as the distinction between a deep pink and light purple often catches me out.

The scientific name for this wiry plant, Succisa pratensis, reveals a link to a medicinal use in bygone days. It was sought out as a solution for certain skin conditions, including scabies and eczema.  The devil element of the common name nods to the legend that the roots of the plant were shortened as they had been bitten off by the Devil, who had taken umbrage at the supposed healing properties of the plant. The Latin word succido, means ‘cut-off below’.

It isn’t just in Scotland that the plant is popular, in 2007 the Jersey Post Office issued a set of wild flower stamps and one of those featured was devil’s-bit scabious. So there you have it. An interesting, native wildflower, popular with pollinators and people. How could you not love a plant that looks like a pom-pom and goes by the name of ‘bobby bright buttons’?

The sweet smell of success

By Athayde Tonhasca

Flowering plants – the angiosperms – underwent a rapid and profound diversification during the Cretaceous period (145 to 66 million years ago), so that they became the most diverse group of land-based plants. Their abrupt and rapid rate of species radiation puzzled and bothered Charles Darwin because the scale of transformation suggested an uncomfortable and significant exception to his deeply held belief in natura non facit saltum: nature does not make a leap. Angiosperm radiation occupied much of Darwin’s thoughts, and he referred to the problem as ‘a most perplexing phenomenon’, ‘nothing… more extraordinary’, and an ‘abominable mystery’, which became one of his most memorable quotes.

Timeline of plant evolution and the beginnings of different modes of insect herbivory © L. Shyamal, Wikimedia Commons.

Despite all the data accumulated since Darwin, the abominable mystery lingers on; for one thing, palaeontologists and molecular biologists don’t always see eye to eye about interpreting the evidence. But whatever the explanation for the radiation of angiosperms, insect pollination (entomophily) is believed to have much to do with it: flowering plants and their pollinators depended on each other for reaching their level of species richness, making it the most celebrated case of coevolution.

The success of the flowering plant-pollinator relationship depends on plants’ ability to attract insect visitors, which is achieved by a variety of flower advertisements such as size, corolla shape, orientation, colour, and scent. Of these, scent must be the least understood of flower lures; the development of gas-chromatography techniques started changing that.

Floral scents are complex mixtures or volatile organic compounds (VOCs) emitted by the petals and other tissues. Some of these chemicals mimic insect pheromones that dupe pollinators into coming to the flower hoping to find a mate, a place to lay their eggs, or to feed. But most VOCs are the ‘flowery’ types, scents that are pleasant to us such as benzyl acetone, which is one of the most abundant attractants in flowers (you are likely to have smelled it from cocoa butter, raspberries, soaps, perfumes, etc.).

A woman making potpourri, a source of benzyl acetone © Herbert James Draper (1863–1920).

Even though VOCs are metabolically costly and may attract unwanted visitors such as herbivores, many plants produce an array of complex scent blends that often appeal to particular pollinators. We know little about how insects distinguish specific chemicals in these mixtures, but they are quite good at it. Their olfactory sensitivity has profound consequences: any tweak in floral chemistry can change completely the character of visitors. This was demonstrated experimentally by Shuttleworth & Johnson (2010) for pineapple lilies (genus Eucomis) from Africa. These plants are difficult to tell apart based on flower appearance: they all look alike with a greenish-white colour, and their nectar is comparable. But plants containing two sulphur components in their floral aroma are visited by carrion flies (families Calliphoridae, Muscidae and Sarcophagidae); those that do not are visited by spider wasps (family Pompilidae). And here’s the thing: the addition of these two chemicals to wasp-pollinated flowers provoked an immediate shift to fly pollinators: the ‘missing stink’ was found. This result suggests that a radical shift of pollinators is one short step away, with no need of sweeping changes in a plant’s other properties.

The autumn pineapple flower (E. autumnalis) is pollinated by spider wasps, which are replaced by carrion flies when flowers are laced with sulphur compounds © Ton Rulkens, Bernard Dupont and Toby Hudson, respectively. Wikimedia Commons.

In South America, petunias (Petunia spp.) also comprise species with distinct pollinators. The large white petunia (P. axillaris) has white flowers with long, narrow tubes and produces abundant scent: this plant is pollinated by nocturnal hawk-moths. The rare, endemic and threatened P. exserta has a bright red corolla and no scent. As one would expect from a plant with colourful and scentless flowers, it is pollinated by hummingbirds. Klahre et al. (2011) observed that the ability to produce scent or not for these two petunias depends only on two genetic loci (specific positions on a chromosome). This relatively simple genetic characteristic suggests that loss or gain of odour properties – and therefore of pollinators, just like the pineapple lilies – can happen with relative ease, for example by hybridisation.

Large white petunias © Magnus Manske, and the endangered P. exserta © scott.zona, Wikimedia Commons.

Sometimes the plant itself takes care of changing its aromatic profile for the sake of self-defence. In the south-western United States, the flowers of coyote tobacco (Nicotiana attenuata) usually open at night (18:00-22:00 h) and release benzyl acetone. This chemical draws in the five-spotted hawk-moth (Manduca quinquemaculata) and the tobacco hawk-moth (M. sexta), who pollinate the flowers. But there’s a catch: the larvae of these moths feed on the plant, sometimes extensively. Kessler et al. (2010) noticed that high numbers of five-spotted hawk-moths induce the coyote tobacco to open its corollas between 06:00 and 10:00 h, and to reduce the production of benzyl acetone. Day-time flowers with a weak scent are no longer that attractive to hawk-moths, but they are fine for hummingbirds, especially the black-chinned hummingbird (Archilochus alexandri). Why then doesn’t the coyote tobacco stick to day-flowers and save energy by doing away with benzyl acetone? Probably because hawk-moths are better pollinators, since they are attracted to scent over large distances.  

A coyote tobacco with its trumpet-shaped flowers (ideal for long-tongued pollinators), a five-spotted hawkmoth and a male black-chinned hummingbird © Dcrjsr, Muséum de Toulouse and Mdf, respectively. Wikimedia Commons.

These observations and experiments highlight the importance of scent for pollination services, and the potential for radical changes in plant-insect relationships caused by apparently minute twists in floral chemistry. Nature takes care of these modifications, but geneticists have noticed the implied opportunities for plant selection.  

Benzyl acetone, the sweet smell of success ©Edgar181, Wikimedia Commons.

East Ayrshire Energy

The creation of a new hedge for wildlife, consisting solely of pollinator-friendly native species, is just one of a range of impressive habitat creation projects carried out by the energetic Countryside team at East Ayrshire Leisure Trust. A whopping 1,500 hawthorn, blackthorn, dog rose, elder, and crab apple saplings were planted in Kilmarnock’s Dean Castle Country Park in 2022.

As with many planting projects, aftercare is vitally important. The team behind the planting will continue to monitor the new hedge on a regular basis. Mind you that’s a practice they are well-versed in. The newly-planted section is an addition to an existing lengthy hedge of native species planted between 2020 and 2021, stretching to almost a kilometre!

At the Kennedy Drive side of the huge Dean Castle Country Park an area of space was given over to a mixture of plants which have created a pleasant orchard area. Sweet Chestnut, Hazel, Whitebeam, Elder, Cherry, and Apple species combined with Plum, Black Currant, Red Currant, Gages, and Quince to create more pollinator-friendly habitats within the park and the wider district.

The understory hasn’t been ignored in this striking body of work. The path sides were seed-bombed with Forget-Me-Not and there are plans to sow Yellow Rattle in the coming months.

Yellow rattle and red clover, in a wildflower meadow.

It isn’t just in the impressive Country Park that actions have been taken place.

Wildflower seeds and a bit of the Countryside Coordinator’s time, and special know-how, were provided to help St Patricks Primary School in Auchinleck improve their immediate surroundings for the benefit of pollinating insects.

A crocus with a bumblebee covered in pollen grains. ©Lorne Gill/SNH. For information on reproduction rights contact the Scottish Natural Heritage Image Library on Tel. 01738 444177 or http://www.nature.scot

As part on an ongoing project to naturalise areas, and encourage people to become more involved in deciding on the look of their local green spaces, East Ayrshire Greener Communities have been working with schools and local residents groups to implement an ambitious programme of wildflower projects. These have embraced spring bulb planting, annual wildflower plug planting, along with highly impressive swathes of tree planting.  The outcome has been the creation of a pleasing array of beneficial areas of biodiversity.

That shift to empowering communities is a major part of a very inclusive approach to managing and creating popular community green spaces. Projects of this nature will continue to be rolled out over the next two years, providing pollinator habitats whilst forging strong partnerships with lively communities.

Another pronounced change has been particularly welcome news for pollinators. Reduced and delayed verge cutting allowed the majority of plants to flower before access management issues required to be addressed. Wildflower areas and woodland glades are not cut until late summer/autumn, if indeed at all. The cutting when it arrives is generally to discourage colonisation by trees and retain open habitat.

Last year East Ayrshire Woodlands created two new wee forest areas (approximately 2000m2) which included a diverse range of flowering tree and shrub species, whilst allowing ground flora species to thrive. Near Knockmade Moss the council planted 700m of mixed hedge along the roadside – amounting to 3,500 hedge plants including rose, holly, blackthorn, hawthorn, hazel, crab apple, and elder.

In Dunlop’s Wee Glen East Ayrshire Woodlands carried out extensive ‘tree surgery’ to increase light levels within the wood which have better allowed the woodland ground flora to thrive. Allied to the removal of regenerating beech, rhododendron and bamboo this all worked to favour native species. Where the existing roadside hedge had gaps these were plugged with native species.  Lying on the eastern edge of Dunlop the site, which is owned by Woodland Trust is well worth a visit.

East Ayrshire Council has an area of over 1,200 square kilometres to manage, and the wishes of around 122,000 residents to accommodate.  That’s a big commitment, and it is great to know that pollinator provision is high on their busy agenda.

Images courtesy of James MacDonald, East Ayrshire Countryside Development Officer, except for wildflower meadow and bumblebee on crocus images which are (c) Lorne Gill/NatureScot

Pollination converts

By Athayde Tonhasca

Pirate bugs (genus Orius), also known as flower bugs, live up to their name: although small (adults are 2-5 mm long), they are aggressive and rapacious predators, taking any quarry they can handle. Thrips, mites, aphids, whiteflies, scale insects, small caterpillars and eggs of various insects, are all potential prey. They also feed on sap and pollen to complement their diet. Pirate bugs may ‘bite’ you (in fact, they pierce skin with their proboscis) while you work in your garden. Despite this unfriendly behaviour, pirate bugs should be welcome: they are efficient exterminators of a variety of crop and horticultural pests, and some species are commercially available as biological control agents.

A minute pirate bug (Orius insidiosus) feeding on whitefly nymphs © Jack Dykinga, Wikimedia Commons.

The word ‘bug’ is commonly used for all sorts of insects and other small creatures. But for entomologists, a bug refers only to members of the order Hemiptera such as aphids, scale insects, cicadas, leafhoppers, and assassin bugs. So hemipterans such as pirate bugs are known as true bugs. These insects have specialised mouthparts adapted for piercing and sucking liquids. As a consequence, most of the 75,000 or so bug species in the world are plant feeders. Some, like the aphids, can be serious agricultural pests because they damage plants and transmit viral diseases. Most of the remaining species are predators, like the pirate bugs; a few are parasites, feeding on their hosts’ blood (e.g., kissing bugs, bed bugs and bat bugs). 

Insects like the hibiscus harlequin bug (Tectocoris diophthalmus) cannot bite or chew: they stab their host or prey with their spear-like mouthparts and siphon their contents © Sam Fraser-Smith, Wikimedia Commons.

Because of their life style and feeding habits, bugs are some of the least likely candidates for the tasks of transporting pollen and fertilising flowers; indeed, these insects are invariably ignored as players in the pollination game. But this view was challenged when Ishida et al. (2008) looked into the pollination ecology of the macaranga or parasol leaf tree (Macaranga tanarius) on the Amami and Okinawa Islands (Japan). This plant is a common pioneer species in disturbed rainforests through south-eastern Asia, Australia and the western Pacific islands. It turns out that the macaranga seems to be mainly pollinated by the pirate bug Orius atratus. Another hemipteran, Decomioides schneirlai, also visits macaranga flowers in significant numbers, but no evidence of pollen transport was found. 

These bugs belong to two genera known to be predators, so how come they – or at least one of them – became pollinators? The answer seem to be related to the macaranga flowers’ structure. Their bracts (the modified leaves positioned beneath the flowers) are rounded and tightly enfold the tiny flowers. Both bugs manage to squeeze through and enter the enclosed chamber formed by the bracts, which is a safe place to mate and for their larvae to develop. 

A macaranga tree © Tatiana Gerus, and Macaranga sp. bracts enveloping the flowers © Forest and Kim Starr, Wikimedia Commons.

But these bracts have more to offer to flower visitors. They bear nectar glands, a characteristic shared by many plants in their family (Euphorbiaceae). In the case of the macaranga, the nectaries scattered at base of the bracts are covered with trichomes (‘hairs’) and are protected by a thick cuticle. So nectar is out of reach to most visitors, except bugs: armed with powerful mouthparts, they can pierce the nectaries and indulge themselves in the sugar-rich solution. By enticing bugs with a place to mate, breed and feed, the macaranga tree acquired some unusual pollinators.

A typical Euphorbiaceae inflorescence. s: style; ff: female flower; jmf: juvenile male flower; o: ovary; b: bract; pff: pedicel of the female flower; i: involucre; g: gland; bo: bracteole (a structure between the bract and the bloom) © Frank Vincentz, Wikimedia Commons.

The bug-pollinated macaranga seemed to be an eccentricity until Etl et al. (2022) examined the reproduction of the arrowhead plant Syngonium hastiferum in the forests of Costa Rica. Most species in this group of aroids (family Araceae) are pollinated by beetles, but S. hastiferum broke the mould. Thanks to a series of modifications such as scent composition and time of release, pollen morphology and production of food rewards, this plant dropped beetles and adopted a bug as its pollinator: a yet to be named species in the genus Neella. These bugs belong to the family Miridae (mirid bugs, plant bugs or leaf bugs), a large group of plant feeders, some of them serious agricultural pests. 

L: Hundreds of Neella sp. plant bugs on an inflorescence of S. hastiferum (scale bar 1 cm); R: bugs dusted with pollen grains while leaving the inflorescence (scale bar 5 mm) © Etl et al., 2022.

What these examples from Japan and Costa Rica teach us? First, they exemplify plants’ incredible capacity to adapt and explore opportunities that give them a competitive edge. Sap-sucking bugs are generally unwelcome pests, but if they also transfer pollen efficiently and reliably, plants may co-evolve with them to contain their damage while encouraging their pollination services. Second, bug pollination is not likely to be restricted to these two cases. As new studies show us again and again, we have much to discover in the field of pollination: time will tell whether one of these long-beaked creatures help pollinate members of our local flora. 

A Good Year

Those of you familiar with the Russell Crowe film about sun-drenched Provence may have stumbled here by mistake. My apologies. But if your interest is more pollinator monitoring than South of France then it has indeed been ‘A Good Year’ and you have in fact come to the right place.

PoMS (the UK Pollinator Monitoring Scheme) provides one of the most robust measures we have of how our pollinators are faring. There is increasing appreciation of the key role pollinating insects play in our environment, so many of our crops and wild plants are reliant on their pollination service, and in an era beset by biodiversity loss, climate change and food security, to name but a few challenges, we need to know how pollinator populations are changing. 

The key to understanding what is happening in the natural world is reliable information, and 2022 was a good year on this front.

PoMS is (to quote the website): “The first scheme in the world to have begun generating systematic data on the abundance of bees, hoverflies and other flower-visiting insects at a national scale. Together with long-term occurrence records collated by the Bees, Wasps and Ants Recording Society and Hoverfly Recording Scheme, these data will form an invaluable resource from which to measure trends in pollinator populations and target conservation efforts.”

The PoMS partnership, can trace its roots back to 2015, and is very much a collective effort, a coming together of agencies, academic institutions, conservation organisations and individuals and an example of collaboration at its best. 

Conservation and monitoring rely heavily on the input not only of dedicated national bodies and energetic environmental groups, but also on motivated individuals. The PoMS FIT Counts (Flower-Insect Timed Counts) and 1 km² surveys are a prime example, both engaging volunteers to undertake surveys supported by the core team. And the news from these highly engaging surveys is impressive.  In autumn of this year the first four years of data from PoMS FIT Counts and 1 km² surveys were published on the NERC EIDC data base. In the course of four years the number of records has steadily increased, and the information gathered is available for everyone to view. 

The eagle-eyed amongst you might have noted that 2020 is the end date in the dataset above. Don’t be concerned. The data have continued to pour in after 2020. As with all large-scale citizen science schemes, these data require a significant amount of checking and processing to reach the publication stage, especially in the case of the 1km square surveys where specimens of bees and hoverflies are collected and require identification by experts to produce a record.

New technology has been harnessed to make recording simpler. It is now roughly 18 months since the project’s FIT Count app went live, and in 2022 the app generated around half of the 3,790 FIT Counts submitted overall. We can all agree that it has been a roaring success and made sending in results much slicker.

As well as compiling robust data the UK PoMS team have been collaborating with various regional initiatives to encourage more people to submit FIT Counts online. They gave an excellent insight on this at the well-attended Cumbria Wildlife Trust’s ‘Big Buzz’ National Pollinator Conference, and worked with the “Nature isn’t Neat” project in South Wales using FIT Counts as a way of engaging local communities with pollinators and measuring the success of habitat restoration efforts. 

The environmental world has long been good at collaborating, sharing data and spreading the word. 

PoMS work is no exception, and regular contact with groups such as Bumblebee Conservation Trust, Butterfly Conservation, the British Trust for Ornithology and Buglife is a key strand of the approach being taken. Increasingly the partnership seeks to reach out to students who want to carry out pollinator studies, and to the academic community which is already busily engaged with pollinator-related work. These are vital components of gaining a more rounded picture of pollinator issues.

Image courtesy and © Katty Baird

Let’s end with another quote from the UK Pollinator Monitoring Scheme website … “With reports of dramatic losses of insects occurring across the globe, and concern about what this means for wider biodiversity and ecosystem health, there has never been a more important time to document evidence of change in populations of pollinating insects.”

Do look out for the start of the 2023 FIT Count season in April, it’s a sure-fire route to greater knowledge in the quest to help our hard-pressed pollinators.  And who knows, you might just be blessed with time in the great outdoors that is as captivating and bright as a proverbial sun-kissed Provencal vista?

Notes:

Follow PoMS on twitter @  https://twitter.com/PoMScheme

Enjoy the UK Pollinator Monitoring Scheme website @ https://ukpoms.org.uk

Videos:

FIT Count introduction: https://www.youtube.com/watch?v=9wQHhc8Q7_g

UKCEH video on pollinator monitoring:    https://www.youtube.com/watch?v=i7vqbyxMD1M

Acknowledgement:

The UK Pollinator Monitoring Scheme (PoMS) is a partnership funded jointly by UKCEH and JNCC (on behalf of Defra, Scottish Government, Welsh Government, and DAERA). UKCEH’s contribution is funded by the Natural Environment Research Council award number NE/R016429/1 as part of the UK-SCAPE programme delivering National Capability. PoMS is indebted to the many volunteers who carry out surveys and contribute data to the scheme.

Just can’t wait to get on the road again

By Athayde Tonhasca

The publication of On the Origin of Species is 1859 is unquestionably one of the most significant episodes in the history of science. Charles Darwin’s and Alfred Russel Wallace’s theory of evolution by natural selection caused such a commotion that one of the book’s other idea didn’t get much attention at the time of publication. For one thing, Darwin dedicated a little over one page to it: the suggestion that evolution is not always the product of a struggle for existence, but sometimes is driven by sexual selection. Or, in Darwin’s own words, by ‘a struggle between the males for possession of the females’.

Darwin was stumped by the fact that natural selection could not explain obvious differences between males (producers of many small reproductive cells or gametes – the sperm) and females (producers of fewer, larger gametes – the eggs) of many creatures. Why should it be that male lions have manes, male deer sport massive antlers, many male birds are endowed with bright and colourful plumage, while their female counterparts have none or subdued versions of those features? Even worse, some characteristics appear to hinder survival and thus cannot be explained by natural selection. Darwin vented his vexation in a letter to American botanist Asa Gray: ‘the sight of a Peacock’s train whenever I gaze at it makes me sick’.

This Indian peafowl’s (Pavo cristatus) covert feathers (its train) would be tricky if the bird is chased by a tiger in their native Indian forest © Paul Lakin, Wikimedia Commons.

But Darwin’s aggravation didn’t last long, as he elaborated the theory of sexual selection in a subsequent book: The Descent of Man, and Selection in Relation to Sex (1871). In it, he suggested that features in some individuals (males or females) give them advantages over individuals of the same sex solely in respect of reproduction, even though these features could be harmful in other circumstances. Sexual selection operates from differences in mating success, whereas natural selection results from variability in other fitness traits. For psychologist Geoffrey Miller, ‘natural selection is about living long enough to reproduce; sexual selection is about convincing others to mate with you’.

In The Descent of Man, Darwin wanted to provide evidence that evolutionary principles – including sexual selection – apply to humans. This cartoon from Fun magazine (1872) mocks his ideas. The caption reads: That Troubles Our Monkey Again – female descendant of Marine Ascidian: “Darwin, say what you like about man; but I wish you would leave my emotions alone“. 

Sexual selection would work in two ways: through direct competition between males (or less commonly between females), so that contestants become larger and acquire showy ornaments or weaponry, or by female choice (or less commonly by male choice), where mates are picked based on their perceived quality as parental material. In the case of peacocks, a female would choose a male with the most flamboyant train, which indicates vitality, health, survival skills, and so on. And by showing off his colourful appendage, the male signals to the female that her offspring would have a better chance of survival if he was their daddy.

A figure from The Descent of Man, depicting a male (top) and a female of the suitably named Atlas beetle (Chalcosoma atlas).

For Darwin, morphological differences between males and females (sexual dimorphism) are the expected consequences of sexual selection. Since then, evidence has suggested that natural selection can also lead to sexual dimorphism; for example for some birds, differences between males and females in bill morphologies appear to be the result of dissimilar foraging habits (e.g., Tomotani et al., 2022). The current view is that sexual dimorphisms, expressed as differences in appearance, internal morphology and biological functions, are the result of all selective pressures – natural selection and sexual selection – on males and females.

For many invertebrates, females are larger than males, possibly because females need to produce lots of eggs and defend their brood; for birds and mammals, size is biased towards males, a likely result of intra-male competition. L: Female (left) and male banana spiders (Argiope appensa) © Sanba38; R: A male northern elephant seal (Mirounga angustirostris) towering over a female and a pup © Mike Baird, Wikimedia Commons.

Sexual dimorphism is one of the most pervasive traits in some plants and many animals, and its consequences are far and wide. For us humans, besides the obvious dissimilarities in size, muscle mass and fat distribution, men and women differ in the risk of contracting some diseases, absorption of drugs, response to therapies and vaccination, and so on. That’s why health researchers are increasingly being required to distinguish the sex of their subjects in clinical trials (e.g., Willingham, 2022).

Naturally, sexual dimorphism is found in bees as well, and it is manifested primarily in their haplodiploid system of sex determination, where unfertilized eggs result in males and fertilized eggs result in females. But bee dimorphism is also expressed in a range of traits such as body size, morphology, coloration, physiology and behaviour, all attributes linked to the roles played by each sex for the species’ survival. Females take care of nest construction and brood provision; in the case of social species such as honey bees (Apis spp.) and bumble bees (Bombus spp.), they maintain and defend the nest. Males on the other hand are driven by one main objective: to seek females and mate with them. So they have no pollen-carrying structures or stingers. This rather narrow life plan has not helped the reputation of males, which have been labelled lazy, free-loading sperm donors. But drones (male honey bees) help with maintaining a hive in good order, and males of many species are better pollinators then their female counterparts.

Hind legs of a male (L) and a female bee, which has a scopa – a cluster of stiff hairs to harvest pollen
© Chelsey Ritner, Exotic Bee ID, USDA.

Males of many bee species have another trait, one that could be essential for protecting the species against habitat disturbances: they are hopeless wanderers.

Most bees are solitary (each female builds her own nest) and philopatric, which is the tendency to stay in or return to the site of their origin. Females prefer to nest near the place of their birth because food or good nesting sites could be scarce elsewhere – why take chances with the unknown? This tendency to stay put may result in huge nest aggregations (e.g., the heather colletes, Colletes succinctus). But philopatry induces inbreeding, which doesn’t bode well for the future of a population. Males, however, who do not have a home or offspring to care for, can fly away in search of a mate outside the old, boring neighbourhood. Sexual attraction is governed by pheromones, and males of some species such as the vernal colletes (Colletes cunicularius) show a preference for scents produced by females from different populations (Vereecken et al., 2007).

A male vernal colletes, looking for love somewhere else © Aiwok, Wikimedia Commons.

The sugarbag bee (Tetragonula carbonaria), a stingless species endemic to Australia, demonstrates males’ dispersing capabilities. They roam an average of 2-3 km from their nests, more than twice the female range, to find a mate; some males cover 20 km, about 30 times the females’ range (Garcia Bulle Bueno et al., 2022). By dispersing over great distances, males are bound to transfer genetic material from one population to another, which is especially important if the species’ habitat has been fragmented by human activity. 

A sugarbag bee © Ken Walker, Museum Victoria, Wikimedia Commons.

The role of male dispersal in reducing the effects of inbreeding was inferred from the genetic structure of populations of the oddly named unequal cellophane bee (Colletes inaequalis) in an urban/suburban habitat in New York, USA (López-Uribe et al., 2015). This bee is solitary, but females nest close to each other in aggregations of up to 100 nests/m². Sampled bees had greater genetic similarity within nest aggregations than bees chosen at random, an expected consequence of philopatry. But there were no signs of inbreeding among the 11 nest aggregations spread over approximately 40 km², an indication of genetic exchanges between them. And there’s more: within nest aggregations, females were genetically more inter-related than males, a sign of sexually biased migration rates. These DNA analyses elegantly suggest that males are the main arbiters of genetic flow among unequal cellophane bee populations.

A: a female unequal cellophane bee at the entrance of her nest. B: A nest aggregation © López-Uribe et al., 2015

Sexual dimorphism has been largely attributed to intra-species competition, often in the form of males fighting each other for a female or to be chosen by one. But sexual dimorphism has a cooperative side: it allows males and females to specialise in what they do best, be it caring for the young, finding food, defending territory, and so on. In the case of bees, males do their bit by gallivanting around, and by doing so they help reduce the risks of inbreeding.