Pollination Partnerships by Heather Angel
Heather Angel has spent much of her long career in professional photography investigating and documenting the fascinating adaptations of both animals and plants. Tim Harris asked Heather to tell us more about her fascination with the subject of plant pollination. Heather also reveals the stories behind some of her favourite pollination images, many of them revealing intriguing pollination partnerships. A wider selection of her work can be viewed in our new gallery of her pollination images.
Not all plant visitors are pollinators
Spotting an insect (or any animal) feeding on a flower does not prove they are pollinators; for instance a butterfly with outstretched wings could be sunbathing. It helps if an image captures which part of the body picks up pollen, so the camera angle is crucial.
Bee-flies often hover as they feed on nectar. Viewed head-on a large bee-fly (Bombilius major) withdraws its pollen-laden proboscis from an honesty flower. Unlike butterflies, bee-flies fly with the proboscis outstretched, so much of the pollen is transferred to the next flower it visits.
Day gecko lapping nectar
A day gecko (Phelsuma sp.) laps up nectar from a crown of thorns (Euphorbia sp.) in Madagascar. I spotted it outside a restaurant but it scuttled round to the back of the flower. After each course, I nipped out, with no luck after the starter and main course. Finally, I was rewarded after my dessert, capturing the gecko with its the red tongue feasting on nectar!
Pollen pick-up on butterfly wings
A Chinese peacock butterfly (Papilio bianor) sips nectar from a hibiscus flower in Yunnan, China. The position is maintained by flapping the wings, which pick up pollen on the underside from the stamens placed on the end of a long column. Butterflies that visit flowers with a narrow tube to access the nectar may pick up pollen on their proboscis. A green praying mantid lurks on the right…
Drone fly upside down on snowdrop
Winter flowers with rewards – including snowdrops – are visited by pollinators, but only on fine days with little wind and temperatures above 0°C. Insect visitors include drone flies (shown here), honeybees and bumblebees, which hang on upside-down. When the proboscis or a leg touches the open end of any of the six anthers, orange pollen falls onto their undersides.
SPP – Secondary pollen presentation
Exposed pollen on the petal edges of a newly opened St Helena ebony (Trochetiopsis ebenus) is a surprising sight. Known as secondary pollen presentation (SPP), it occurs when pollen from the anthers is transferred to another part of the flower in the bud stage. Here, the anthers face outwards and release pollen onto the petal margins before the bud opens. This makes it more accessible to small insects alighting on open flowers. Once the flower opens the pollen does not last long, especially if wind buffets the flower around. SPP is not uncommon in the Campanulaceae family.
Rare red nectar
Red nectar is not commonly seen in flowers. I first saw it in Hawaii, when I upturned the bell of a Mauritian bloody bellflower (Nesocodon mauritianus). Back in the 1970s a single population of the bellflower was discovered on a cliff beside a waterfall. Some years later, the species was propagated from seed at the Royal Botanic Gardens Kew. The natural pollinator is a native gecko (Phelsuma ornata) that lives in the cliffs nearby.
The Californian tree poppy (Romneya coulteri) has large white petals and a huge cluster of stamens. Female leaf cutter bees (Megachile centuncularis) have special pollen-collecting hairs (scopa) on the underside of their abdomen. This bee is dual-tasking by collecting pollen and pollinating the flower as it perches atop the stigmatic disc. In the foreground, a dead head hoverfly (Myathropa florea) also feeds on pollen.
Some flowers use deceitful mimicry
Some flowers are deceitful by mimicking a reward that does not exist. Small begonias (Begonia semperflorens), common as bedding plants, have stigmas in female flowers that look like a mass of yellow pollen-laden stamens. But they are fake. Nonetheless, they lure pollinators which, if carrying pollen, land on them and effectively pollinate the flowers. However, they are unlikely to pay a return visit once they realise they have been duped!
The embrace of the hoverfly
A marmalade hoverfly (Episyrphus balteatus) steadies its body by resting all six legs on the stamens of viper’s bugloss (Echium vulgare) in the Italian Dolomites. It then wraps the proboscis round an anther to feed on the blue pollen.
Cyclamen flowers are buzz-pollinated by bumblebees. Here, high speed flash in a studio captures pollen release from a pore at each anther tip, triggered by mechanical vibration, which replicates sonication by a bumblebee. The upside-down flower, with upswept petals and the opening at the base, protects the pollen from rain damage.
Photographing pollinators at night is more difficult than by day. A head torch with an optional red light for finding and focusing on insects is preferable to white light, which disturbs many moths. The camera angle is key, preferably showing a moth’s proboscis inserted into the flower. A macro flash lighting set-up is ideal. Here, an angle shades moth (Phlogophora meticulosa) is nectaring on snowberry (Symphoricarpos x chenaultii).
How foxgloves and bees work together
As a female wool carder bee (Anthidium manicatum) enters a rusty foxglove (Digitalis ferruginea) flower in a Surrey garden, pollen transfers to the head from anthers, just beneath the upper lip of the flower. Male bees often cruise around these flowers looking for a potential mate, sometimes landing on a female and knocking her off onto the ground.
Honeybee feeding frenzy
A feeding frenzy of honeybees pull stamens free to access pollen from Magnolia grandiflora flowers. In the USA the pollinators of this tree are beetles and the magnolia controls when the insects enter and leave the flowers. They open at dusk when a sticky lemony secretion amongst receptive stigmas attracts the beetles; pollen from incoming insects is deposited on the stigmas. The flowers then close, trapping the beetles inside. During the night, the anthers start releasing pollen. In the morning the flowers open, so the beetles escape carrying a fresh pollen load on their sticky bodies. In Surrey, honeybees converge on the fallen stamens and collect pollen without aiding pollination.
Wasp with pollen load
The purple stamens of Spanish love-in-the mist (Nigella hispanica) mature before the stigmas. When the flowers open, both stamens and styles are upright. Gradually, the stamens bend down, so the anthers lie in a horizontal plane. Honeybees and wasps circumnavigate to sip nectar from the ring of turquoise and white nectaries. Their bodies just fit below the anthers that swipe across their back, depositing pollen on their hairy bodies. A few days later, the stigmas bend down sequentially, ready to pick up pollen from bee or wasp bodies.
Ultraviolet light shows slipper flower’s pollination strategy
Darwin’s slipper flower (Calceolaria uniflora) occurs in Tierra del Fuego, Chile. Instead of pollen or nectar as a reward, this flower has a sweet fleshy white lip. The pollinator is the least seedsnipe. As a bird walks to a flower and bends to pluck off the sweet lip, pollen transfers from the two stubby stamens onto the bird’s head. In UV light, the focus stack clearly shows the lower lip and two stamens with exposed pollen that both reflect UV, with the rest absorbing UV. This highlights the position of the lip very clearly.
Many of Heather’s pollination images feature in her book Pollination Power, published by Chicago University Press with Royal Botanic Gardens Kew. We’ve created a new gallery featuring many bookplate images and illustrating pollinations partnerships, as well as some brand new material. Here is a taster of some of the bird pollinators illustrated:
After looking at some of Heather’s favourite pollination images and hearing the stories behind them, we wanted to know more about how Heather became fascinated by the subject matter of pollination partnerships. We also asked about the challenges she faced in taking these photos, and her thoughts for the future…
TH: What first attracted you to pollination as a subject for photography?
HA: “Most of my working life as a wildlife photographer has involved travelling extensively to capture original images of wildlife, often for books I was writing. Whilst I was waiting for animals to appear or wake up, I began to look at flowers and spotted a few pollinators. Gradually, over many years, they have often become my main targets. Within the last decade, I have concentrated on my original passion, namely close-ups and macro, which was an essential technique when I began taking photos of marine invertebrates with my very first camera. ”
TH: What were the trickiest technical challenges in capturing these images? And have advances in camera technology helped?
“Way back in the 1960’s I took my first monochrome UV images of flowers using an entomological lamp as a UV light source and a Hasselblad camera with a Polaroid back, to gain virtually instant viewing. An evening primrose was the first flower I discovered with a dark bull’s eye pattern from the petals’ bases absorbing UV. So, after I started taking colour UV images with a UV flash, I chose the same flower. The central UV pattern, with the nectar drop visible fluorescing, attracts nocturnal insects. ”
“With active pollinators there is often very little time to select the best camera angle to show on which parts of the insect’s body pollen collects, before it flies off to the next flower. So, the success rate is nowhere near 100%. A walk around our garden one night in August 2015, revealed two solitary bees using a peach-leaved bellflower (Campanula persicifolia) as a bivouac. This meant I had to use flash, but as this campanula has a deep bell, the only way to get it all in focus was to take a focus stack. After I downloaded the 19 images and completed the focus stack, I saw neither bee had twitched an antenna – such perfect subjects! ”
Digital capture allows me to quickly check that images are in focus in the right places (sometimes an insect moves just as I release the shutter) before I move on. The ability to change the ISO at will is a huge benefit. Now we have the chance to produce stitched panoramas, take focus stacks of small three-dimensional subjects to enhance the depth of field. We can also make shots with extremes of exposure over the frame possible with High Dynamic Range imaging (HDRI). ”
TH: What are your thoughts on the recent reports of the catastrophic decline in insect numbers and the potential impact this could have for plant pollination?
HA: “The decline in insect numbers won’t impact the pollination of all flowers equally. Wind-pollinated flowers won’t suffer. Those that have open access to nectar and/or pollen such as ivy and many open bowl flowers including single roses, tulips, crocuses and dahlias have a variety of insect visitors that aid pollination. It is the more intricate flowers with, for example, nectar hidden in a long spur that only long-tongued butterflies and moths can reach that are likely to suffer. Via the process of co-evolution, any flowers that are pollinated by a single specific insect with a perfect fit, will not survive if their pollinator dies out.
The other problem is global warming, which affects mountain flowers that appear in snow-melt areas. When snow melts earlier, they bloom earlier – sometimes out of sync with the time when their pollinators emerge. But it is not just flowers that will decline, this will also affect our food plants. Pumpkins, squashes, cucumbers, runner and French beans, tomatoes, apples and pears are just a few examples of food we take for granted, which requires cross pollination for maximum crop yield. Tomatoes grown outside are naturally buzz-pollinated by bumblebees. When grown on a commercial scale, specially bred colonies are used. More recently, ingenious ways to mimic natural buzz pollination include the use of electric toothbrushes to release the pollen.”
TH: What were the most intriguing “pollination partnerships” you came across while working on the Pollination Power project?
“Nectarless feijoa (Acca sellowiana) flowers provide sweet fleshy petals as a reward for tanagers that pollinate them in Brazil. As they bend down to snatch a petal the head is dusted with pollen from the staminate anthers. Here a wood pigeon in Surrey has plucked a whole flower, so the anthers have not deposited pollen on the head.”
“Many lilies are pollinated by butterflies that flap their wings which pick up pollen as they sip nectar. For days I was puzzled why I saw no insects visiting huge lilies with conspicuous yellow flowers and bags of pollen in the Russian Caucasus, yet all the pollen was gone by late afternoon. I solved the mystery when on a pre-breakfast sortie I discovered small hoverflies busily eating the pollen!”
TH: You studied zoology and became a marine biologist. How did you become so knowledgeable about botany and plant identification?
HA: “My maternal grandmother taught me the names of wildflowers in Suffolk lanes when I stayed each summer holidays on my grandparents’ farm. This encouraged me to look at flowers near my home and to identify them. Later, when I travelled abroad, I made a bee-line for botanic gardens, so that I could see what plants were in flower. I also spent a year studying botany at University and now spend quite a lot of time researching.
TH: Are there pollination stories you have not yet photographed and would like to cover in the future?
HA: “Many, for sure – scientists discover new pollination partners every year – especially in South Africa and Western Australia which have such rich floral kingdoms. I should like to capture an endemic Mauritius gecko lapping up red nectar from the blue Mauritius bellflower, but apparently it requires abseiling down a cliff, with my gear, to reach the few remaining wild plants. By continuing to add plants to our garden, specifically to attract and capture winter and nocturnal pollinators, I shall have plenty of subjects to photograph throughout the year. Maybe 2020 will be the year I begin to capture video clips of pollinators in action ……”
To view more of Heather’s amazing images of pollination partnerships, take at look at our new gallery. And if you’d like to order a copy of Heather’s book, it is currently available on special offer from the Royal Botanic Gardens Kew website.
And if you’d like to order a print of any of Heather’s pollination images, you can find a gallery of her work on our print site, available to order as prints, greetings cards, jigsaws and a range of other products. To claim a 15% discount until 20th December 2019, please quote offer code NPLXMAS.