Sonicate to pollinate

By Athayde Tonhasca

For most species of flowering plants, fertilization depends on the transfer of pollen from the male anthers of one flower to the female stigma of another. 

© Dianaperezval, Wikipedia Creative Commons

For the majority of those flowers, pollen is released through the splitting open (dehiscence is the technical term for it) of mature anthers. But for approximately 6% of the world’s flowering plants, pollen is kept locked inside non-dehiscent anthers and accessed only through small openings – pores or slits – in their extremities. We refer to them as poricidal anthers. 

Left: stamens, consisting of filaments and anthers. Most flowers release pollen by the splitting of the anthers along a line of weakness (top right); some only do it through a small hole or pore (bottom right) © Wikipedia Creative Commons

Sometimes the whole flower has a poricidal arrangement, as it is the case for the tomato and related plants (Solanum spp.). Pollen is concealed inside a cone-shaped cluster of fused stamens and can only be released though a pore at the tip. Botanist say these flowers have a solanoid shape, after the name of the plant genus. 

Solanoid-shaped tomato flowers © Muffet, Wikipedia Creative Commons

Extracting pollen from poricidal structures is not easy, but some bees know a way to do it. 

A bee lands on one of these flowers, bites an anther and curls her body around it. She then let out bursts of fast contractions and relaxation of her thoracic muscles – those used for flying, but here the wings don’t move. This produces cyclical deformations of her thorax that last from fractions of a second to a few seconds, and can be repeated many times (think of a body builder flexing his pectoral muscles really, really fast). These movements generate vibrations that are transmitted to the anther, causing pollen grains to fall though the apical pores and land on the bee’s body, perhaps aided by electrostatic forces. Watch the whole sequence of events here and here. 

This fancy pollen-harvesting manoeuvre creates a high-pitched buzz, hence it is known as ‘buzz pollination’; or as ‘sonication’ in technical reports. A physicist or an engineer could point out that this mechanism is not strictly sonication because it’s not sound that agitates and extracts pollen (such as in this example), rather direct vibrations on the flower. But ‘sonication’ is the term commonly adopted, so we will keep it. Bumble bees (Bombus spp.), carpenter bees (Xylocopa spp.), and some other bees can buzz pollinate: honey bees (Apis spp.) and most leafcutter bees (Megachile spp.) cannot. And apparently only females know the trick; males have never been recorded buzz pollinating.

A bee engaged in buzz pollination © Bob Peterson, Wikipedia Creative Commons

Plant species with poricidal floral morphology are distributed across at least 80 angiosperm families, which suggests that buzz pollination has evolved independently many times. This has probably been helped by bees’ readiness to buzz for other reasons such as warning potential enemies, compacting nest materials, or cooling/warming their nest with wing beats.

Buzz-pollination syndrome, the name given for this plant-bee association, is not just a biological curiosity. It makes a huge difference for crops such as tomatoes, raspberries, cranberries, blueberries, aubergines, kiwis and chili peppers. These plants don’t necessarily need buzz pollination to reproduce, but they produce more and better fruit if they are buzzed because more pollen is transferred and more ovules are fertilised.

In the late 1980’s, Belgian and Dutch companies developed techniques to rear on a large scale the buff-tailed bumblebee (Bombus terrestris), the ultimate buzz pollinator. Local producers of greenhouse tomatoes began replacing costly mechanical pollinators with boxes containing bumble bee hives, and a global, multi-million pound industry was born. Today, every tomato bought in a European supermarket has matured with the help of a commercially reared bumble bee.

A commercial bumble bee hive used in greenhouses © Elaine Evans, The Sustainable Agriculture Research and Education

We may see pollination as a harmonious relationship where plant and insect go out of their way to help each other, but this is mistakenly romantic. A bee aims to take all the flower’s pollen: pollination happens because a few grains are dropped or rubbed off by accident. And a plant produces as little nectar and pollen as necessary to entice a flower visit. So the association between pollinators and flowers is best described as a mutual exploitation. Buzz pollination fits nicely into this scenario. Poricidal anthers prevent excessive pollen expenditure by rewarding only buzz-pollination specialists, which increases the chances of pollination. Plants with poricidal structures typically secrete little or no nectar but their pollen is rich in protein, which convinces a bee to go to the trouble of buzzing to gain a small dose of the yellow stuff. It’s a clever, efficient trade agreement in the pollinator’s world.

The star of the show

Should you ever find yourself in Edinburgh’s Trinity or Newhaven areas, and seeking some relaxing greenspace, then head for Starbank Park. You won’t be disappointed. Here you will find a green oasis, sure to soothe and re-energise in equal measure.

Starbank is well-connected, not just physically but socially. Starbank House – which still sits in the park – was once owned by Alexander Goalen, You may not have heard of him, but you will recognise the name of a distant relative of his, the four-time British Prime Minister William Gladstone. 

Looking out over the Firth of Forth the park boasts a rich mix of trees, flower beds, areas devoted to herbs, and much more besides.  There is interest all year round.  In a few weeks time the cherry trees here will deliver their wonderful annual display, and pollinators will make the most of the feast this offer.

The Keep Scotland Beautiful ‘It’s Your Neighbourhood’ scheme is nothing short of a modern national treasure.  When they opened up a Pollinator Friendly award it chimed with many community and volunteer groups. The Friends group at Starbank Park were one such group and keen to submit an entry. In went an entry that was glittering with pollinator-friendly practices. From top to toe their’s was a submission up with the very best.  As Janet McArthur explained their approach mirrors the intentions of putting nature at the very centre of this category.  

“We encourage pollinator-friendly planting through our planting plans. We have planted many bee friendly bulbs and have a wide selection of fruit trees, shrubs and annual flowers to feed a variety of pollinators. It’s an important element of our planting action plan that we choose plants, herbs and flowers which are attractive to pollinators throughout the year. In short we want to attract as many pollinators to our community garden as possible by creating a welcoming habitat in our neighbourhood. That’s why we did little things too like put up a few bee hotels in our nature trails.”

They have followed up those inspiring words with a range of impressive actions.

Even the pandemic couldn’t stop them in the tracks. 

Janet takes up the story.  “When lockdown began we knew we needed to try to bring the spirit of the park to people’s homes. We kicked off a sunflower competition encouraging our community to participate in growing this nectar rich plant. This resulted in some spectacular sunflowers grown by all ages (and we now have a young volunteer working with me) which I’m sure really cheered people up in the late summer months. Appreciating the challenge our community had in obtaining seeds during the early weeks of lockdown we opened up our seed library to those interested in growing a little bit of Starbank Park in their own gardens, patios or window boxes.”

And the good news didn’t end there.  

There has been a significant pollinator bonus in a wonderfully ambitious switch from bedding plants to annuals. Keeping a park vibrant and appealing is not an easy task. It requires impressive detail as well as breadth. One of the most admirable actions is the seemingly straightforward one of leaving dandelions to flower in the park for hungry early bumblebees. That might seem an easy step on the surface, but in parks this is switch from the old engrained ethos of neatly manicured lawns that requires a bit of explanation and engagement to convince folk that things are actually being managed better for nature rather than simply being left to go to ruin.  

That job of persuasion and convincing was well done and now it is another popular and beneficial move for pollinators that is part of the ethos here.  

The Friends of Starbank Park formed in October 2013 and have not only restored this park to its former glories but carried forward a range of activities and actions that have engaged the local community. Today local schools, edible growing projects and space for toddlers are all part and parcel of a very broad appeal. There are even a couple of ‘little free libraries’ where locals share and swop books.

My own experience of parks is mixed, but of late the swing has been towards nature and community friendly spaces. Starbank combines pleasure, practicalities and pollinators in what is, by any standards, a really pleasing mix.

Find out more and visit:

Starbank Park are active on social media and have an excellent website which gives a lovely flavour of the delights that wait in store. The park also has a regularly updated twitter feed.

The park has a lot to offer at any time of the year.  If you would like to see the cherry trees in bloom, weather depending, the first week in May is a good date for your diary!

A welcome migrant?

By Athayde Tonhasca

If you spot a bumble bee in a garden, park or street from now until July, there’s a good chance it will be a tree bumble bee (Bombus hypnorum). Which is remarkable, considering this species was not even recorded in Britain until 2001. From the first sightings near Southampton, the tree bumble bee took Britain by storm: it has spread throughout England, Wales and much of Scotland. This represents an expansion of about 56 km/year. Today this species is often the most abundant bumble bee in urban and semi-urban environments. 

The tree bumble bee has a unique colour pattern among British species: ginger-brown thorax, black abdomen and white tail © Graham Ekins, The Essex Field Club

One of the characteristics that helped the tree bumble bee make itself at home in Britain is being a synanthrope. From the Greek syn (together) and anthropos (man), this term refers to species that benefit from humans and their habitats. Cockroaches, house sparrows, pigeons and the brown rat are quintessential synanthropes: their distribution and even survival depend on people. The tree bumble bee doesn’t go that far, but its life is greatly improved by our presence. Most bumble bees – most bees, in fact – nest on the ground, and appropriate sites are sometimes scarce. The tree bumble bee, as its name suggests, prefers to nest high up in a tree cavity. But many manmade structures above ground level such as bird boxes, compost bins, gaps under roof tiles, house eaves, and holes in walls and fences are perfectly suitable substitutes. And these sites are usually not disputed by other bees.

Compared to other bumble bees, the tree bumble bee starts the season early and forages at short distances from the nest. It also feeds on a wide variety of flowers, has a high nest density and may have two generations per year. Some or all these factors may have contributed to its success. Whatever the reasons, the speed and reach of tree bumble bee invasion have few parallels among alien species. 

An endearing creature such as the tree bumble bee is frequently referred to as ‘a recent arrival’, ‘a welcome addition to the UK’s fauna’ or ‘a newcomer’, because ‘alien’ has bad connotations. Alien species (those introduced outside their normal distributions) are often assumed to be harmful, therefore demanding eradication or control. But this is misguided. Most introduced species are neutral, as they neither damage nor help the environment. Some are beneficial, improving ecological services or providing food for native species.  Others become invasive, that is, they are harmful to habitats or other species. And bees can be invasive, such as the buff-tailed bumble bee in Asia and South America or the giant resin bee (Megachile sculpturalis), which is spreading in continental Europe and is known to displace native bees. 

So is the alien tree bumble bee a non-invasive species? Apparently, yes. So far it seems to cause no harm to other bees, and it may contribute to the pollination of our crops and wild flowers. But if its numbers keep increasing, other species may feel the nudge of competition. We have to wait and see.

Other bees seem to be fine with the newcomer, but its synanthropic nature has raised some human eyebrows. Tree bumble bees may take over bird boxes by expelling existing occupants, and their nesting sites may feel too close for comfort. Some people are also apprehensive at tree bumble bees’ apparent ‘swarming’. These are drones (male bees) hovering near a nest entrance, waiting for the opportunity to mate with a virgin queen flying from or into the nest – watch it. These events are called nest surveillances, and can last several weeks. But since drones are stingless, like all male Hymenoptera (bees, wasps and ants), nest surveillances are harmless.

A local arrival of tree bumble bees provokes spikes in calls to local authorities, beekeepers and pest controllers from people who want reassurance or, in a handful of cases, to get rid of bees buzzing nearby. Although most people are thrilled to have bumble bees as their close neighbours, this may change if bee numbers increase much further. Once again, time will tell.

The tree bumble bee, just like the ivy bee, seems to be a benign alien. But the consequences of its expansion are being watched closely.

Bumblebee conference broadens horizons

You can’t go out and see bumblebees anywhere other than on your doorstep these days, but that doesn’t mean you can’t hear all about them.  A couple of Saturday’s ago I joined a pan-European video conference and got what you might term ‘a continental pollinator fix’.

The European Bumblebee Conference subjects were many and varied, and truth be told I felt that I had been on a fantastic journey when the conference closed.  It is impossible to do them all justice here, so I can point you to them all online @ https://www.bestuivers.nl/hommelsymposium.

Vincent Kalkman of the Naturalis Biodiversity Centre of Leiden, chaired the conference, and opened proceedings by saying “Why he disliked bumblebees”. This proved a rather tongue-in-cheek title. He explained there were aggravating similarities between some species, and variations of colour within species, that make for difficult field identification between the likes of terrestris and pascorum.  He summed this up by saying “They seem easy to understand, but in fact their identification can drive you insane and understanding their requirements is mind-boggling!”  It was a good scene-setter for some great presentations.   

Challenges were the focus of the very first talk – ‘Mind the gap’ – by Bristol University’s Thomas Timberlake.

He highlighted the problem of seasonal floral resource gaps for bumblebees, particularly on farmland. Despite progress via Agri-Environmental schemes, the timing of floral resources remains an obstacle that future schemes could tackle.  Plant species have distinct flowering windows, which results in a seasonal pattern of nectar and pollen availability. Sometimes there is more than enough to go around, but at other times – like the early-spring and late-summer – there is a dearth of forage for bumblebees.

For bumblebees like this one (Bombus terrestris), it’s not just about how much food is available, it’s also when that food is available through the year. A dandelion flowering in early spring for example, would be more valuable to a bumblebee than an equivalent flower in mid-summer. Image: T. Timberlake 

Tom looked at foraging patterns of emerging queen bumblebees and young queens preparing for hibernation in farms in the South-West of England. The lack of September nectar on farms highlighted the potentially positive role of adjacent gardens as a consistent supply of nectar. 

How to boost resources in late summer?  Planting late-flowering cover crops, sowing margins with beneficial seed mixes, improving hedgerow quality, and introducing late flowering species (especially red clover, ivy and scabious) were all offered as actions which would have a positive effect.

Species which flower in September such as dandelions, red clover, ivy and scabious (clockwise from top left) are likely to be disproportionately important to bumblebees and other pollinators. Including these and other late-flowering species in conservation schemes will help fill the late summer hunger gap. Images: T. Timberlake & Wikimedia Commons

Paolo Biella gave us an inspirational update on bumblebees in the Alps. As a key part of bumblebee life-cycle is dedicated to collect resources, he intercepted Bombus terrestris returning to their nests which were, by scrutinising their pollen, found to be visiting 34 or so plant species, thus confirming their generalist feeding and how plant diversity is important for pollinator diet, even at high altitude.

More than 50% of Europe’s bumblebee species are found in the Alps – that’s around 39 species. – despite the area accounting for around just 10% of Europe’s surface. Paolo looked at the habitat requirements of three alpine species to see if any distribution changes could be identified in since the 1980s. Temperatures in the areas studied have risen, narrowing environmental resources to cold-adapted bumblebees and making them more sensitive to changes. All three were shown to be feeding at higher altitude now.

Given that the Alps is a core area for many European bumblebees, it was a sobering and thought-provoking presentation.

Working in partnership was a constant theme across the presentations. This came across vividly in the presentation by Nikki Gammans (Bumblebee Conservation Trust) which was a practical exploration of working with farmers. 

Based around the reintroduction of the Short-haired bumblebee, Nikki explained that Kent is the UK’s hot spot for rarer bumblebee species and that they tend to be late emerging and longer tongued, factors that influence targeted habitat creation. 

The aim was to work on a landscape scale, and this could only be effectively done by connecting working farms. Connections provided by Natural England opened up avenues to explore agri-environment schemes and the options for individual farms by giving bespoke advice. 

Management and maintenance methods were explored to enhance the prospects for flower-rich meadows. Grazing regimes, field margins, cutting cycles, seed mixes and rotation of stock also fell under the spotlight. The honest appraisal that patience is essential for work that can take between 5 and 9 years to show significant changes, and acknowledging the value of advice from the farming community, wrapped up a most impressive talk.

Indeed each and every one of the talks was inspirational and educational. From the Netherlands, to the Himalayas, via the Alps and the south of England.  Too much ground was covered for me to capture it all in a short blog, but hopefully the above gives a flavour of what was presented and encourages you to log in and explore:

To see the presentations visit https://www.bestuivers.nl/hommelsymposium.

About the organisers: Based in the Netherlands, the European Invertebrate Survey (EIS Foundation) shares knowledge on insects and other invertebrates and conducts and promotes research to aid policy and management to help insects in The Netherlands. More at  https://www.eis-nederland.nl

Sweet, sweet poison

By Athayde Tonhasca

In 401 BC, an army of Greek mercenaries led by Xenophon crossed Anatolia (modern day Turkey) to seize the throne of Persia. Xenophon kept a diary of the expedition, entitled Anabasis, or ‘The March of the Ten Thousand’, which today is a classic of ancient Greek literature. Among many battles and other adventures, the commander described one curious episode. His troops come across an abundance of honey, and some of the men went for it with gusto. In no time they regretted their excess: they could not stand up, vomiting and suffering from diarrhoea. Xenophon’s army had been overpowered by honey. ‘So they lay, hundreds of them, as if there had been a great defeat, a prey to the cruellest despondency. But the next day, none had died; and almost at the same hour of the day at which they had eaten they recovered their senses, and on the third or fourth day got on their legs again like convalescents after a severe course of medical treatment.’ (Anabasis, Book IV).

The march of the Ten Thousand. Image in the public domain

The Romans had their own taste of Anatolian honey, this time with grimmer consequences. In 97 BC, General Pompey the Great led an army across Turkey in pursuit of king Mithridates of Pontus, an old enemy of Rome. The local people, known as the Heptacomitae, withdrew. But they left an unpleasant gift for Pompey’s men, possibly on Mithridates’ orders. The geographer and historian Strabo tells us what happened: ‘The Heptacomitae cut down three maniples [around 1,500 soldiers] of Pompey’s army when they were passing through the mountainous country; for they mixed bowls of the crazing honey which is yielded by the tree-twigs, and placed them in the roads, and then, when the soldiers drank the mixture and lost their senses, they attacked them and easily disposed of them.’ 

Strabo’s ‘crazing honey’ that incapacitated those Greek and Roman troops is known today as ‘mad honey’. It comes from nectar produced by the common rhododendron (Rhododendron ponticum), which is endemic and abundant in northern Turkey. This plant is full of grayanotoxins, a group of toxic substances that protect it against herbivores, but also accumulate in the nectar. 

Common rhododendron, a source of mad honey © Rasbak, Wikipedia Creative Commons

Rhododendron honey is eaten in tiny amounts by local people for its perceived medicinal, hallucinogenic or aphrodisiac properties. But an adventurous gourmet taking even a spoonful of the stuff risks being struck by a long list of unpleasant and dangerous clinical symptoms. Indeed, it is not uncommon for people in Turkey – some of them tourists – to end up in the hospital after experimenting with mad honey. For reasons not yet known, invasive plants have lower levels of grayanotoxins than native plants, so mad honey is not a problem here in the UK.

A plant that secretes toxic nectar may seem to be engaged in self-harm, as this sugar-rich substance is the main incentive for pollinating insects to pay a visit to its flowers. But hundreds of plant species produce nectar laced with secondary compounds such as alkaloids, terpenes and phenolics, which are noxious or unpalatable to pollinators. And rhododendron’s mad honey is not unique: pure honey from mountain laurel (Kalmia latifolia) and bog-rosemary (Andromeda polifolia), for example, have a range of possible ill effects on people, including death. So there must a reason for this apparent paradox. Toxicity may be a way of excluding inefficient pollinators, reserving the metabolically expensive nectar for a few specialists that are immune to secondary compounds. It may also discourage nectar robbers, that is, flower visitors who avoid contact with the floral reproductive structures and therefore do not pollinate. Some of these chemicals may have antimicrobial properties that preserve the nectar. Perhaps toxicity is just incidental: secondary compounds act as chemical defences against herbivores, so seepage into nectar may be unavoidable. Poisoning a few pollinators would be a small price to pay for immunity from plant grazers. 

Sources of honey to be avoided: mountain laurel and bog-rosemary © Vlmastra (L), Pmau (R), Wikipedia Creative Commons

The bees that produce mad honey, the Caucasian (Apis mellifera caucasia) and Anatolian (Apis mellifera anatoliaca) honey bee subspecies, seem to be immune to grayanotoxins. So, too, are bumble bees, who take full advantage of rhododendron’s profusion of nectar-rich flowers. But other honey bee subspecies and some solitary bees are not: they die, or become paralysed, sluggish or erratic after consuming R. ponticum nectar (although honey bees learn to avoid rhododendron flowers). 

The common rhododendron is an incredibly efficient pioneer species. Each plant produces more than a million small seeds that are dispersed by the wind over large distances. It forms a dense canopy that shades out other plants, and it may release chemicals that inhibit the germination and growth of other seedlings. And thanks to grayanotoxins and other phenolic compounds, rhododendron has few grazers and sap feeders. Not surprisingly, this plant is a serious invasive wherever it grows unchecked. It is threatening natural and semi-natural habitats in Britain, much of Western Europe, New Zealand, and even in its native range in the southern Black Sea Basin. 

A Perthshire native woodland invaded by rhododendron © Lorne Gill/NatureScot

Because of its nectar, common rhododendron may contribute to the reduction of pollinators’ populations either by intoxicating some bee species or by decreasing food availability for others (invaded areas have fewer alternative flowers). It may also shift local species composition, leaving fewer solitary bees and more bumble bees. Indeed, colonies of the white-tailed bumble bee (Bombus lucorum) and the common carder bee (Bombus pascuorum) occur at higher density in areas invaded by common rhododendron when compared to uninvaded areas. We have no idea of the long term consequences of these disturbances to pollinator communities, but they are not likely to be trivial. Toxic nectar is one more reason for keeping common rhododendron on the list of bad gardening ideas.

Torino’s green vision

It’s undeniably one of Europe’s great cities. Home to the iconic Fiat Lingotto building, the famous Turin Shroud, birthplace of Cavour – Italy’s first prime minister. Steeped in compelling history, industry and culture, an economic powerhouse. Framed by distant views of the dramatic Alps and stunning baroque architecture Torino seemingly has it all.

However, this is a city that looks forward as well as over its shoulder, and good green infrastructure and pollinator-friendly projects are very much in vogue in Piedmont.

Torino is at the cutting edge of Italy’s evolving green infrastructure ambitions. Along with cities including Zagreb, Dortmund and Ningbo (China) it is part of the proGIreg project which is adopting nature-based solutions to transform post-industrial cities. It’s a project that will run until at least 2023 and has drawn a deal of praise.

There are eight agreed nature-based solutions being applied, and some of them, such as accessible green corridors, green roofs and walls, pollinator-friendly approaches and community based gardens, are familiar elements of Scotland’s evolving green infrastructure approach too.

There is an admirable, dynamic green vision to make the famous Piedmont capital a healthier and more environmentally friendly city for residents and wildlife.

Having a positive mind-set certainly helps. Take the Orto Wow project for example, based in the Mirafiori Sud district — a classic post-industrial neighbourhood near the old Fiat Factory — once synonymous with manufacturing. As we have learned in a post-industrial Scotland, when big industry relocates it can leave behind a legacy of brownfield sites, decaying and derelict buildings and sizeable transportation scars.

Orto Wow overcomes the undoubted challenges of transforming a former industrial neighbourhood by harnessing the collective power of partnership working. Their bold plans skilfully draw on the considerable expertise of the city council, university departments, and enthusiastic local associations.

The upshot is the creation of a green oasis, with centre stage perhaps the impressive pollinator garden (with no fewer than 16 raised beds). The idea is to create a city ‘pasture’ for bees and other pollinators.  It should succeed, as it has been worked up with the input of the highly respected University of Turin, and in planting classic pollinator-friendly plants such as borage, calendula, thyme, chives, dandelions and wild mustard a guaranteed feast for pollinators is on the menu. 

The increase in pollinator-friendly surroundings goes beyond the conventional. The proGIreg group in Torino created two large green walls to cover the Night Hospitality House in Corso Tazzoli. It gives new life to a once vacant building and the soothing green infrastructure fits well with the belief that urban greenery can contribute positively to health and well-being.  Regenerating former industrial buildings and making them available for new community ventures whilst greening their fabric is a bold, positive development that the locals are understandably proud of. 

It is worth dwelling on the fact that green walls have more than pleasing aesthetic qualities. They reduce noise, filter the air, and help cool buildings – a particularly welcome benefit as Torino can be a hot city in summer.

The ability of good green infrastructure to contribute to citizens’ health and well-being is also evident in the bold ‘Farfalle in ToUr’ project. The project focusses on butterflies, and began in the central district of Cenisia. By creating an urban butterfly oasis the project seeks to help the city on many levels. At the most basic level habitat is restored and connectivity improved for species. However, by engaging with a raft of citizen scientists, which includes both staff and patients from local mental health centres, vital monitoring work can be run in parallel with enhancing social inclusion and tackling mental health issues – all by tapping into the positive influence of involvement with nature.

A city commitment to steadily remove pesticide usage dovetails with moves to ensure green spaces are geared to offer forage and shelter for bees, hoverflies, butterflies and other pollinators, whilst the green networks themselves will act as corridors to better link potentially isolated populations of pollinating insects. This is fitting in a city which hosts one of the three major Italian lepidoptera research group in the University of Torino’s Department of Life Sciences and Systems Biology.

ProGIreg are evidence-based in much of their work. They have two pollinator transects inside Piemonte Park, one between the allotments and one in a wide meadow close to the River Sangone. Since 2018 bees and butterflies here have been surveyed to assess the specific impact of nature based solutions. The butterfly monitoring is the first Italian butterfly monitoring scheme using urban transects.

Physical health will also benefit from the pollinator friendly networks in Torino. The evolving parks, green corridors and river banks around the city support active travel ambitions are good for people and nature alike. A series of pleasant cycle paths allow for safer, healthy active travel routes from the periphery into the city centre. Routes along the banks of the River Sangone (as it flows towards the mighty River Po) typifies the delivery of a cycling plan formalised by the development of Torino’s ‘Biciplan’ to increase cycling to 15% of all 5km trips in the city.

The reassessment of public spaces is also gathering momentum. Piemonte Park is being dramatically redesigned and used for community urban gardens, the drive has included new social farming activities to help with teaching, training and creation of job placements. The social farming project (Orti Generali) is creating interest beyond the city as even small details deliver notable benefits, for example something as simple as animal grazing results in savings for park maintenance budgets.

A particular challenge faced in Torino is being situated in a valley associated with low levels of natural ventilation. The greening steps are going to prove key if the city is to overcome occasional poor air and meet its environmental ambitions. Like all cities there are financial challenges to overcome, but the green approach is clearly gaining momentum.

We may associate Torino with Fiat, Bicerin and Juventus for a bit longer, but the signs are that positive change is afoot in this famous Piedmont city.

With sincere thanks to Francesca Martelli for all of her help with this article.

Why entomologists kill

by Athayde Tonhasca

Some people are disturbed by the sight of insect collections: those rows and rows of butterflies, bumble bees, beetles and other beautiful insects impaled with steel pins seem wrong. Many wonder if such killing is needed, and if it could be damaging to biodiversity.

Entomology collections at the National Museum of Natural History, USA © Chip Clark, Smithsonian Institution,Wikipedia Creative Commons

The first thing to have in mind is that insect populations are usually huge and fluctuate enormously, often by orders of magnitude. Spells of bad weather and surges of natural enemies (predators, parasites and diseases) kill insects by the hundreds, thousands or even millions. But thanks to their prodigious reproductive capacity and short generation spans, insects quickly recover from periodic population crashes. Insects die naturally by the truckload and are born by the truckload, so a few entomologists with their butterfly nets really do not measure up to important mortality factors, and will not even dent populations of most species. The greatest danger to most invertebrates lies elsewhere – the loss of habitats. Collecting can be a hazard for a few localised, rare species, but in these cases entomologists and researchers in general follow codes of conduct to prevent or minimise serious damage.

But why is collecting necessary?

The main reason is to obtain voucher specimens. These are samples of catches that are deposited in a collection for reference. Vouchers authenticate the identity of an organism at a certain place and time, help us recognise threatened species, and are also an insurance against erroneous records. Species identification may be tricky, even for expert taxonomists. It often requires examination of complex morphological details under a microscope after special preparation such as softening, cleaning and dissection: no photograph can replace this work. 

A voucher specimen deposited in a collection © Natural History Museum

Species records and inventories are constantly corrected by re-examination of museum specimens following taxonomic advances. For example, in 1900 it was recognised that bees recorded in UK as the wall mason bee (Osmia parietina) comprised another species as well, the mountain mason bee (O. inermis) which is known only from the Scottish Highlands. But the plot thickened: in 1981 entomologists realised that some bees identified as O. inermis were in fact the pinewood mason bee (O. uncinata), another rarity from the Highlands. These updates are not capricious: they result from more data and new information. The consequence is that records of these three species before 1981 are unreliable without vouchers. 

Wall, mountain and pinewood mason bees: it’s not easy to tell them apart. © Arnstein Staverløkk, Wikipedia Creative Commons.

Insect collections are libraries of the world’s biodiversity. They help us to identify invasive species potentially harmful to agriculture, forestry, and human and animal health. They teach and educate the public, and are critical for training; even experts rely on museum specimens to confirm identifications and improve their skills. 

Collecting is essential for inventories and biodiversity work. By sampling and identifying the species at a given location, researchers can recognise biodiversity hotspots, determine which areas should be set aside for protection, and assess whether management practices are working. For example, samples of aquatic insects are used extensively for measuring the water quality of rivers and other water bodies because many species are highly sensitive to pollutants. An ongoing UK-wide monitoring project has given us better understanding of population trends and distribution of hundreds of species of pollinators. 

Pan traps to collect pollinators. © Parys, K.A. et al. 2020. Agronomy 10(5) 698; https://doi.org/10.3390/agronomy10050698.

Specimens in museum drawers offer us an understanding of the past and the present, and also help us predict the future. A comparison of decades of museum records of a North American butterfly has shown that Mexican populations were four times more likely to have gone extinct than Canadian populations. These results demonstrated a northward shift of the butterfly, a likely consequence of climate change. Analyses of pollen attached to bees collected at different time periods have given us much information about the consequences of agricultural intensification and population trends.

None of the arguments above address the moral aspects of killing animals. Many an ethicist has debated this, but one thing seems clear to them: those who object to collecting for scientific purposes should also object to their killing for selfish and trivial reasons, which include swatting wasps on picnics, baiting fish with crickets, and spraying insecticides on munched flower beds. We have limited understanding of insects’ levels of cognition and sensations, although almost certainly they are not conscious or able to feel pain the way mammals do. Even still, no sensible entomologists take the killing of insects lightly. In their hearts, they follow Joseph Greene’s advice: “Collect by all means, but let it not end with the catching or acquiring of specimens; let it lead to a knowledge which shall have some practical bearing hereafter. Do not be too much of a collector, or too much of a ‘sorter’ of species, ever striving to compass within hard-and-fast lines that which is illimitable.” (The Insect Hunter’s Companion, 1880).

 

A lasting legacy

It is estimated that there are over 300,000 miles of rural road verges in the United Kingdom. Around 700 species of wildflower grow on these verges, representing a whopping 45% of our total native flora.  What we needed was a guide to help us manage this remarkable resource to best advantage.

Plantlife’s ‘Managing Grassland Road Verges’ has delivered just that. Widely welcomed with open arms by botanists, entomologists and environmentalists this profoundly sensible route map won the prestigious Best Practice and Knowledge Sharing award at the Chartered Institute of Ecology and Environmental Management (CIEEM).

The CIEEM award recognises the outstanding expertise within Plantlife and is set to be a boon for practitioners and nature.

On the surface this well-designed, and easy to navigate, booklet offers practical guidance for road managers, highway engineers, and landscape architects in the management of lowland and upland grassland verges. But it isn’t long before the reader realises that within the covers lies a treasure trove of insight and information.

Amongst the myriad of eye-catching facts in this booklet there is one which perhaps merits the most positive attention.  In managing our verges in a way which is wildlife-friendly we can create a habitat which would equate to the area of London, Edinburgh, Cardiff, Manchester and Birmingham combined.

The multi-functional benefits verges can offer for nature and people are now well recognised. The list includes contributing to improved air quality, carbon sequestration, biodiversity enhancement, pollinator corridors, and better water management.  With the current emergencies around climate change and biodiversity loss uppermost in our minds that’s an impressive list of contributions in anyone’s book.

Some would suggest that a pandemic induced look at our closest surroundings has actually aided this greater appreciation of what well-managed verges can mean for our future.

And, here’s the rub, it’s not difficult to do the right thing.

Currently there are a number of traps we can fall into.  We cut our verges too often, we cut them at the wrong time of year, and the cuttings are left to create a thick thatch which suppresses the next generation of flowering plants. That trio of ‘sins’ in turn increases management costs, and misses an opportunity to help biodiversity, thus a golden opportunity slips through our fingers.

The guide emphasises how we can turn that ship around and steer a better course.  It plots a route to create a network of species-rich verges, resplendent with native wildflowers and carrying the ability to support much more wildlife, particularly pollinators, in ecologically richer networks.

In NatureScot we take particular delight in Plantlife’s richly deserved accolade. They have worked tirelessly to draw this subject into the public mainstream.  Reading the report and thinking about tireless work for grassland, we recall our colleague Jane MacKintosh, who championed grassland for decades, yet sadly passed away before she could see grassland on road verges move up the agenda.

It’s a particular delight to encounter a booklet that is so well sign-posted. The journey from assessing what is in a verge, how to best manage it, and crucially how to monitor its performance is covered in an easy to absorb fashion. The importance of key actions such as regular maintenance and sensitive timings are succinctly and compellingly made.  Timing of mowing is important and it is difficult to provide generic advice for the whole of the UK.  In Scotland alone the timing of cutting will vary a lot between Shetland and the Borders! 

There is a saying that the ‘devil is in the detail’ but in this volume the detail is welcome.  Topics as varied as leaving a patch of bare earth for nesting insects, incorporating floral variety, considering options for enhancing and restoring verges as well as creating afresh – these are subjects that fall under Plantlife’s searing spotlight.

For many of us the most compelling and uplifting section is the one focussing on ‘How to create species-rich grassland verges’.   The reader is presented with a logical step-by-step guide, the language is crystal clear, and there is an insight into what challenges to expect along the way. Problem plant species are tackled head on. The environmental path is seldom a straight line to sunlit uplands.

Politically there has been much talk in recent times about the need to ‘build back better’.  It’s a neat slogan, and in advocating a practical and better way to manage our verges Plantlife can rightly claim to be delivering that mantra, quite literally, on the ground.

Managing grassland road verges – a best practice guide can be found on the Plantlife website.

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Hard beginnings

By Athayde Tonhasca

If you have been out for a walk, you may have seen the odd bumble bee flying about. These are recently emerged queens, who will soon build nests in which to lay their eggs and kick start a new colony. You may also have noticed that the world does not seem quite ready for bumble bees: it is still cold, and there aren’t many flowers around.

Those queens have been underground since last summer, and have loss weight during hibernation. About 1 in 5 did not make it through the winter. Now a surviving queen has to feed on plenty of nectar and pollen, which is necessary for the development of her ovaries. She will be alone for several weeks before her first brood arrives, therefore if she can’t find enough flowers to keep her going through nest construction, egg production and brood care, she will die or not produce offspring.

Not an easy life for this buff-tailed bumble bee queen (Bombus terrestris) © Bj.schoenmakers, Wikipedia Creative Commons.

So March and April are a critical period for bumble bee survival. A queen can’t rely on most crops for food, as they will flower weeks from now. She will find nectar and pollen in early spring plants such as comfrey, heather, crocus, primrose, rhododendron, cornflower, vetches, white deadnettle, willows, hawthorn and blackthorn. You can help by planting early blooming flowers in your garden, backyard, and outside pots. 

Goat willow (Salix caprea) and snowdrop (Galanthus spp.), excellent early sources of pollen and nectar, respectively © Rosser1954 (L) and Redsimon (R), Wikipedia Creative Commons

You may correctly assume that it’s hard enough for a queen bumble bee even if she finds enough food, so it may not be a good idea to be flying around so early in the season. But researchers tracked queen bumble bees with harmonic radar (a useful tool for tracing the path of flying insects) and found out they don’t do much flying at all. Recently emerged queens spend most of their time resting on the ground, only taking short flights now and then. In a couple of weeks they will take off to found new colonies, sometimes several kilometres away. Of course we are more likely to notice the bees that are flying than those that are on the ground, which give the impression that they are all on the wing. We don’t know the reasons for queens staying put after hibernation, but it certainly helps them save energy for the arduous tasks ahead.  

Early risers

Here we go again!  After several months of the cold and prolonged darkness of winter, it’s an eagerly anticipated delight when the first sparkling flowers of the year emerge.  Amongst the highlights are surely twinkling white snowdrops, glossy yellow winter aconites, and the vivid crocus.

For many people the first glimpse of snowdrops is a sure sign that spring is coming. The dazzling white flowers can be a boon for insects and this is a plant that requires no maintenance.  There was a misconception at one time that snowdrops didn’t produce seeds, but they can if there are pollinators about and for any emerging queen bumblebee snowdrops could be a life-saver. 

In some areas the buff-tailed bumblebee is active in winter, and snowdrops can be a great source beyond the likes of Mahonia and winter-flowering heather.

Snowdrop have another endearing quality; they frequently grow in charming drifts comprising hundreds of flowers. As you might expect given their early flowering status, they have an interesting social history. 

Native woodland carpeted with snowdrops (Galanthus nivalis) by the River Almond in Perthshire. ©Lorne Gill

Once associated with Candlemass, which falls 40 days after Christmas, they had a less celebrated association with churches as they were often planted around graveyards which for some meant that snowdrops were related to death.

The snowdrop has range of names across Europe. The French call it perce-neige, ‘the snow piercer’.  And if you have ever seen them poking through snow, you will sense how accurate that name is.

In Spain the snowdrop goes by the name campanilla de la nieves, or snow bell.  It’s a popular flower, and hence has more than one name. Galanto, campanilla de invierno, and rompiendo la nieve (‘breaking the snow’) are just some of the names given to this delightful flower.

The campanilla reference resonates with us here in Scotland, as campanula is the name of the genus for the ever popular Scottish bluebell or harebell Campanula rotundifolia.

As the snowdrop prepares to exit stage, the bright yellow winter aconite assumes centre stage.  This low plant can create a display of vibrant yellow in what is often a dull, grey time of year.  It certainly lifts the spirits of many, and it isn’t uncommon to see it flowering next to snowdrops making for a lovely sparkling display.

The winter aconite, just like the snowdrop, is naturalised in the UK.  It has nothing to do with the ‘real’ aconite.  Instead it’s a member of the buttercup family and loves deep deciduous woodland where it flowers before the tree canopy opens.

Without tree leaves “getting in the way”, light reaches ground level even at this time of year, making the flowers visible.   The flowers reflect UV light, suggesting that they are adapted to attract pollinators which can see this spectrum. As an early source of nectar, winter aconite has a role in helping insects that venture out before spring is fully in swing.

And so to crocuses, where the colour range increases significantly. Spring-flowering crocus is a great source of early nectar and pollen for foraging bees and flies as the days begin to warm up. Indeed, pollen-sprinkled bumblebees on purple crocuses with their vivid yellow stamen are popular with photographers.

More than one spring flowering crocus can be found in gardens.  The most frequently found species in gardens is spring crocus Crocus neapolitanus, from Italy.

The term ‘crocus’ in Spanish is ‘azafrán de primavera’ in effect ‘spring saffron’.  Not to be confused with the Saffron crocus Crocus sativus, which flowers in the autumn – saffron is produced in the central part with Spain, and indeed the area is one of the main world producers. 

It is perhaps worth mentioning that the other autumn crocus, Colchium, is poisonous and should not be confused with saffron.

As with many plants, we can’t be sure of how the crocus made it to Scotland, but it is reckoned it originated from western China, the Middle East and Mediterranean parts of Europe. Again this isn’t a difficult plant to care for, provided the bulbs are not sunk too deeply. And you certainly don’t need to tidy up after them once they have flowered. 

If you want to get your garden or container buzzing, the spring crocus might be just the thing for you. They will add a dash of early colour, and our pollinators will certainly benefit.  Enjoy them this year if you have them, and perhaps plan for next year if you don’t!

With thanks to Terry Swainbank for the opening snowdrop image.