In my new book Birds & Flowers: An Intimate 50 Million Year Relationship I spend a bit of time discussing the idea of the bird pollination syndrome that we refer to as ‘ornithophily’, its limitations, and the fact that it has two distinct meanings that are often conflated. One of the problems with ornithophily, and indeed all of the syndromes, is that historically it’s sometimes blinkered scientists to the extent that they only look at the flower visitors that are “right” for the syndrome, ignoring the rest or dismissing them as “secondary pollinators”, a term I dislike.
Why do I dislike that term? Because it fails to capture the complexity of flower-pollinator interactions and relegates an important component of plant reproduction to a subsidiary role. I could go on about this at some length, but if you’re interested in discovering more, look at pages 62-65 of Birds & Flowers. There I contrast the classical Most Effective Pollinator Principle with the equally valid (but much less well studied) Least Effective Pollinator Principle, with a segue into one of my favourite tracks from Led Zeppelin’s second album: What is and What Should Never Be.
But back to the real subject of this post – a flower that corresponds to the classical bird pollination syndrome BUT is also pollinated by bees and (very surprisingly) wind! It’s such an interesting paper by Brazilian ecologists Amanda Pacheco, Pedro Bergamo & Leandro Freitas – here’s the reference and a link to the study:
For over 100 years the classical pollination syndromes have acted as a framework for understanding the ecology and evolution of plant-pollinator interactions. But we’ve long known that while they can be a useful shorthand, they do not fully reflect the complexity of how pollination systems evolve. That shouldn’t surprise us because, as I point out in my two recent books, we have data (of any quality) on no more than 10% of the 350,000 or so species of flowering plants!
In addition, those plants for which we do have good data are NOT a random subset of the flowering plants: they have been specifically chosen by researchers because they look to be good systems with which to address particular ecological or evolutionary questions.
Which is fine, but we MUST recognise that this imposes significant restrictions on our understanding of the biodiversity of plant-pollinator interactions. The authors of this paper expressed it very well when they wrote that assumptions about:
“predictability may cause researchers to take for granted that only birds pollinate ornithophilous flowers, hindering research on the contribution of other vectors.”
To which I’d add: it also hinders our understanding of how these interactions evolve over long time scales and across multiple populations.
An obvious question is: how frequent are these sorts of complex pollination systems, involving different pollen vectors of an apparently specialised flower? The answer is that we simply don’t know, because most researchers would have not gone into this level of detail. So a huge congratulations to the authors for a great study – I hope it stimulates others to look beyond the ‘expected’ pollinators of flowers.
Photos: Nathália Susin Streher from the original paper.
The final deliverable from the WorldFAIR Project with which I’m involved has recently been published and can be freely downloaded from Zenodo by following the link below. The report is called “Agricultural biodiversity FAIR data assessment rubrics” and in it we present the results from a series of six pilot studies that adopted the FAIR* standards and our recommendations from the previous report.
This document complements the previous one by giving examples and setting out guidelines that allow researchers and practitioners to ensure FAIRness in their plant-pollinator interaction data.
Here’s the full reference:
Drucker, D. P., Salim, J. A., Poelen, J., Soares, F. M., Gonzalez-Vaquero, R. A., Devoto, M., Ollerton, J., Kasina, M., Carvalheiro, L. G., Bergamo, P. J., Alves, D. A., Varassin, I., Tinoco, F. C., Rünzel, M., Robinson, D., Cardona-Duque, J., Idárraga, M., Agudelo-Zapata, M. C., Marentes Herrera, E., Taliga, C., Parr, C.S., Cox-Foster, D., Hill, E., Maués, M.M. Agostini, K. Rech, A.R., Saraiva, A. (2024). WorldFAIR (D10.3) Agricultural biodiversity FAIR data assessment rubrics (Version 1). Zenodo. https://doi.org/10.5281/zenodo.10719265
Although this is the last formal deliverable from our WorldFAIR work package, it’s not the final output that we have planned. I’ll report back on the journal paper(s) that we are writing as and when they are published.
*Findable, Accessible, Interoperable & Reusable (or sometimes Reproducible)
One of the most productive research collaborations in which I’ve had the pleasure to be involved has been with André Rodrigo Rech in Brazil. It started when he was a postgrad working on his PhD, and has now continued as André has developed into fully-fledged academic with his own research group. That productivity has been fueled by a lot of coffee, of course, as you’ll know if you’ve read my book Pollinators & Pollination: Nature and Society!
Here’s the reference – if you want a PDF of the paper, please send me a message via my Contact page:
Pereira Machado, A.C., Baronio, G., Soares Novaes, C., Ollerton, J., Wolowski, M., Natalina Silva Lopes, D. & Rech, A. (2024) Optimizing coffee production: Increased floral visitation and bean quality at plantation edges with wild pollinators and natural vegetation. Journal of Applied Ecology (in press)
Here’s the abstract:
Animal pollination is important for more than 75% of agricultural crops, including coffee, whose productivity can increase with adequate pollination. Bees, including many solitary species, are diverse pollinators, with around 85% of them considered more effective than honeybees in pollen transfer. We assessed the coffee plantation and its surrounding vegetation for solitary bee nesting throughout the coffee flowering season and measured their impact on coffee productivity.
We installed collection stations with trap nests inside a coffee plantation, on the border and inside the native vegetation in a farm in Diamantina, MG, Brazil. We used 10 weekly monitored replicates at least 1 km apart. We evaluated fruiting by autogamy in relation to natural pollination and used the increase in fruit set from pollinators to calculate the farmer’s monetary gain. We recorded bee visits to the exposed flowers during coffee flowering considering both on the edge and inside the coffee plantation. Ripe fruits were dried, counted and weighed.
We discovered 132 solitary bee nests outside the plantation, with 54% containing coffee pollen grains, indicating coffee as an essential resource for bees even outside the crop area. More bee visits occurred at the coffee plantation’s edge, resulting in increased fruit production, denser fruits, and rounder fruits in that area. Bagged flowers produced consistent seeds in all locations. The farmer could earn an extra US$1736.37 per hectare if the entire area received the same level of pollination contribution from bees as observed at the coffee border.
Synthesis and applications. Our study emphasises the key role of pollinators in coffee production and their impact on fruit and seed characteristics. Bee visits were more frequent on border areas, emphasising their reliance on natural nesting sites. Bee-mediated pollination positively affected fruit traits and self-pollinated fruits in plantation borders had reduced mass. Solitary bee nesting was primarily observed in native vegetation, underlining its importance for bee populations. Pollen composition in nests varied with proximity to coffee plantations, indicating landscape vegetation influences pollinator foraging. These findings support optimising coffee plantation design by preserving native vegetation to increase coffee yields and conserve biodiversity.
Yesterday I received an email containing the following press release. I thought it might interest readers of the blog so I am copying it in full with no edits. I had a quick look over the report and it’s amazingly detailed and comprehensive. It’s a shame that the report only covers insects, but that probably reflects my current bias given that my next book, due out in February, is about pollinating birds! Press release follows:
Governor Polis and the Department of Natural Resources Release Pollinator Report
BROOMFIELD – Today, Governor Polis in partnership with The Colorado Department of Natural Resources (DNR), Colorado State University Extension, Xerces Society for Invertebrate Conservation, and University of Colorado Museum of Natural History released the Colorado Native Pollinating Insects Health Study which is the most robust and detailed account of pollinator health ever undertaken in Colorado history. As directed by SB22-199, Native Pollinating Insects Protection Study, sponsored by Senators Sonya Jaquez Lewis and Kevin Priola, and Representatives Cathy Kipp and Meg Froelich, signed by Governor Polis on May 27, 2022, the study assesses the health of Colorado’s native pollinators, evaluates state policies for safeguarding pollinators, and makes recommendations on how to preserve and protect pollinators in Colorado.
“Pollinators play a critical role in Colorado life. From Crested Butte’s beautiful spring meadows to Palisade Peaches and Rocky Ford melons, Colorado’s pollinators sustain our flora and enable many foundational industries in every corner of the state. As our climate changes, we must safeguard the pollinators that generate and regenerate the Colorful Colorado we love,” said Governor Polis
Colorado is home to various native insects and bats whose pollinating services are at the heart of healthy environments and economies. Pollinators are critical to Colorado’s economy and our agricultural production and food systems, and they are essential for flowering plants that support the state’s wildlife ecosystem and add color to Colorado’s beautiful landscapes.
“Colorado is fortunate to have a tremendous diversity of plants and animals, but pollinating insects are perhaps the least studied but most beneficial for our ecosystems, economy and quality of life,” said Dan Gibbs, Executive Director, Colorado Department of Natural Resources. “I greatly appreciate the time and effort of the study authors who truly did a deep dive into the current state of pollinating insects and state policies and structures. I look forward to working with Colorado legislators and stakeholders in pursuing the best policies to ensure pollinating insect protection and long-term health.”
Colorado is home to over 1,000 species of bees—nearly 30% of North America’s and approximately 5% of the world’s bee species—and nearly 300 species of butterflies, representing over 40% of the diversity of butterflies in North America north of Mexico, some of which are already listed under the federal Endangered Species Act. This report underscores the importance of the Polis administration’s goals to tackle Colorado’s greenhouse gas emissions, prepare industries for the impending effects of climate change, and create more sustainable living in Colorado for pollinator populations.
“Our ecosystems rely on pollinators, which is why I’ve championed measures that limit toxic chemicals from harming pollinators and put forth a statewide assessment to better understand the problems our pollinators face and identify practices to better sustain them,” said Senator Sonya Jaquez Lewis, D-Longmont. “Today’s report shows that there’s plenty to do moving forward, and I am looking forward to continuing our work to protect pollinators and the ecosystems that are dependent on them.”
“I’m excited that we have this report to help us understand the extent of pollinator decline in Colorado. While Colorado ranks fifth nationally for the rate of honey-bee die-offs, we haven’t known as much about native pollinating insects. This threatens our food production, biodiversity and health of our ecosystems,” said Rep. Cathy Kipp, D-Fort Collins. “We created the Native Pollinating Insects Protection Study in 2022 to identify ways to better protect and support the native Colorado pollinators, like different bee species, butterflies, and moths, that are also essential to maintaining a healthy environment. These findings will help direct future legislation to create a safer environment for our pollinators, protect our food supply and support biodiversity.”
Promoting policies that benefit native pollinating insects represents an opportunity to foster healthy and sustainable pollinator populations, especially in agricultural and urban habitats. This includes enhancing pollinator-friendly native plantings along I-76 following its designation as a Colorado Pollinator Highway by the Colorado Department of Transportation and other existing state plans such as the state’s Natural Areas Program, and Wildlife Action Plan among others.
“Working on the Pollinator Health Study has been an amazing opportunity to collaborate with so many locally, nationally, and internationally recognized experts in the field of pollinator conservation. In addition to the immense amount of information within the report, this study highlights the importance of collaboration between scientists and land management agencies to bring together the many facets needed for conserving native pollinating insects,” said Deryn Davidson, Sustainable Landscape State Specialist, Colorado State University Extension. “Having the existing research on Colorado pollinators paired with recommended land management practices in one, comprehensive document is an incredible tool for policy makers, land managers, and really anyone interested in actionable steps for pollinator conservation.”
Areas of immediate action and priorities highlighted by the Pollinator Report include:
Priority 2: Protect, restore, and connect pollinator habitats.
Priority 3: Mitigate environmental changes that negatively impact pollinators and their habitats.
Priority 4: Reduce the risks from pesticides to pollinating insects.
Priority 5: Monitor and support native and managed pollinator health.
Governor Polis announced his annual budget proposal on November 1, focusing on ensuring Colorado is more affordable, sustainable, and liveable. The Governor included $100,000 to support education and incentives to encourage the use of pesticide alternatives in agricultural production and residential or commercial landscaping. On May 17, 2023, Governor Polis signed Neonic Pesticides as Limited-Use Pesticides, sponsored by Senators Kevin Priola and Sonya Jaquez Lewis and Representatives Kyle Brown and Cathy Kipp, which protects pollinators from harmful toxins.
The world of nature conservation is fast moving and complex. New opportunities for wildlife and threats to biodiversity seem to arrive almost daily, there are regular high-level meetings focused on conventions and policies, and an endless stream of scientific research being published in the world’s journals. Keeping up with all of this is impossible; trying to keep up with it is exhausting.
For this reason I’ve recently subscribed to Mike Shanahan’s newsletter The Nature Beat on Substack. Mike’s a writer with a background in science research. His PhD was on fig ecology and he wrote an excellent book about the ecological and cultural importance of these fascinating trees called Ladders to Heaven which was one of my five book choices on the Shepherd site.
The Nature Beat is described by Mike as being:
primarily aimed at journalists covering topics such as biodiversity, conservation, wildlife trade, ecological restoration and so on. Of course, non-journalists may also find it useful.
As a non-journalist trying to keep abreast of what’s happening in this complex and rapidly evolving arena, I find it extremely useful! For the past couple of months I’ve opted for the free subscription, but from today I’m going to pay. The kind of insights and expertise that Mike brings to his newsletter are invaluable for anyone interested in how our world is changing, for the worse and for the better. Please subscribe and if you find the content useful, and can afford it, consider upgrading to the paid version.
In the run up to release of my new book Birds & Flowers: An Intimate 50 Million Year Relationship, my publisher, Pelagic, has updated the book description and provided a preview of some of the pages and colour plates – follow this link to view them. On that page you can also pre-order the book direct from Pelagic Publishing, who will ship worldwide, or it’s available from many of the online book sellers.
I’m really excited to be sharing this with the readers of my blog and can’t wait for publication day! Early in 2024 I hope to do some talks, online and in person, to promote the book – so watch this space.
With best wishes to you all and hopes for a peaceful, and more sustainable, New Year.
Obviously the title of this post is click-bait, as there’s LOTS of things that I wish more people knew about pollination! But here’s one that really gets my (Yule) goat.
I’ve lost track of the number of times that I’ve read statements in books and research papers such as “bees collect lots of pollen from flowers therefore they are good pollinators”. Even worse, I sometimes see studies where pollen has been removed from “pollen baskets” or other scopae, then used as a measure of the importance of those bees as pollinators.
In both cases it seems to have been forgotten that bees are collecting pollen to feed their larvae and pollen that ends up in scopae is generally not available for pollination.
That’s the purpose of the Venn diagram at the top of this short post, to remind us that there can be a disconnect between what bees are doing and what plants require: foraging for pollen only partly correlates with flower pollination. Indeed, the same argument applies to any animal that feeds itself or its young on pollen, including pollen wasps (Maserinae), Heliconia butterflies, and some flower-visiting hoverflies, birds and bats.
It’s not only loss of pollen from reproduction that’s important here: depending on the size and behaviour of the bees relative to the shape and size of the flower, they may go nowhere near the stigma, so even if they are carrying viable pollen, it can be lost as far as the plant is concerned.
Note also that many bee species will collect pollen from wind-pollinated plants such as grasses, oaks, etc. Indeed in some species the availability of such pollen is extremely important – see Manu Saunders’ review on this topic and more recent papers that cite it. Again, it emphasises the partial disconnect between pollen collecting by bees and pollination of flowers by bees.
Assessing which flower visitors are actually pollinators is not technically demanding but it can be time consuming. The minimum that you need is single visit deposition (SVD) experiments in which you expose unvisited flowers to one visit by the potential pollinator. Then you assess how much pollen has landed on the stigma or (better) whether the visit results in seed set.
If you want to know more about the evidence that’s required to determine if a flower visitor is or is not a pollinator, they are codified in the “Cox-Knox Postulates” that I discuss in my book Pollinators & Pollination: Nature and Society.
Books are never perfect. In the run-up to publication of Birds & Flowers: An Intimate 50 Million Year Relationship, I am all too aware that this is a truth that’s a cause of anxiety, and sometimes sleeplessness, for all authors. One category of imperfection is tipographical* errors have been introduced at some point in the process of writing and editing. In the past these were corrected in the first edition of a book by the inclusion of errata slips, and such errors are sometimes important in determining the true first editions of older books. On page 20 of the first edition of Darwin’s Origin of Species, for example, there is a misspelling of the word “species”**. This was corrected in the second edition but is an important marker of an extremely valuable book, intellectually and (now) commercially.
A second category involves errors of fact or interpretation or expression that, with hindsight and reader feedback, require correction, or at least acknowledgement, by the author. These are the ones that really make an author squirm inside, even though we know that they are inevitable: we are, after all only human.
It turns out that there are a few examples of both categories in the first edition of my 2021 book Pollinators & Pollination: Nature and Society. Some of them have been corrected in the second edition, but if you purchased the first edition then these are what you should look out for:
P22 – ‘Unmated queens and males (drones) are produced by the colony later in the season’ changes to: ‘Unmated queens and males (drones) are produced by the colony from spring onwards.’
P30, Fig 2.9 – Correct ‘Tabaernemontana’ to Tabernaemontana
P51, Figure 3.8 – title – it should read C. rhynchantha [there’s an h missing]
P57 – ‘The bank that Darwin was referring to is on his property at Down House in Kent, and it was one he observed many times during his walks through the garden.’ changes to ‘The bank that Darwin was referring to is near his property at Down House in Kent, and it was one he observed many times during his walks in the area.’***
P146 – ‘I’ve even see them attack and kill honey bees’ should read: ‘I’ve even seen them….’
P169 – in the title for Figure 10.5, Anon (2019) should be Anon (1919) [in some presentation copies of my book I have corrected this and initialed the change]
P259 – this reference: Klein, A.-M., Steffan-Dewenter, I. and Tscharntke, T. (2003) Fruit set of highland coffee increases with the diversity of pollinating bees. Proceedings of the Royal Society B 270: 955–961. doi: 10.1098/rspb.2002.2306.
Should be replaced by:
Klein, A.-M., Steffan-Dewenter, I. and Tscharntke, T. (2003) Bee pollination and fruit set of Coffea arabica and C. canephora (Rubiaceae). American Journal of Botany 90, 153– 157. doi: 10.1046/j.1365-2664.2003.00847.x
The last two have yet to be corrected and will need to wait for the third edition:
P119 – the Rader et al. study did not include birds and bats, just insects.
P262 – “Nabhan, G.P. and Buchmann, S.” should read “Buchmann, S. and Nabhan, G.P.”
That final error is really embarrassing because, as I point out in the chapter ‘The Politics of Pollination’, their book The Forgotten Pollinators was an inspirational one for stimulating research and action around pollinator conservation! I can offer no explanation for why the order of the authors got reversed in my head.
My sincere thanks to those readers who pointed out some of these errors. My hope is that Birds & Flowers has fewer, but I may be fooling myself…
*You see what I did there?
**Proof-reading is boring and soul-destroying for any author, but really Mr Darwin?!
***If there is an after-life, I’d like to think that Darwin’s now enjoying this error after my snarky comment in the second footnote. To which I’ll respond: watch out for a doozy of a footnote about a Darwin footnote in Birds & Flowers!
There’s so much good science and so many great talks coming out of the (broad) field of pollinator and pollination research at the moment! Here’s a few things that have come up on my radar. Feel free to comment and add your own examples of things I may have missed.
Full disclosure, I was one of the reviewers of Pollinators and plants as ecosystem engineers: post-dispersal fruits provide new habitats for other organisms by João Cardoso et al., and I know that there was quite a bit of back and forth between authors, editor and reviewers about what the findings really meant and how best to frame them. My view was that this study should be published because it’s another demonstration of the importance of pollinators and their interactions with plants that goes beyond the obvious outcomes of plant reproduction and support of pollinator populations.
Back in the late 1990s and early 2000s, whenever I had a (rare) day free from teaching, marking, supervision, meetings, writing, and other university commitments, I would hop on the train from Northampton to London. My destination was the Spirit Collectionof the Herbarium at the Royal Botanic Gardens, Kew, where bottled flowers are preserved in their three-dimensional complexity, rather than squashed flat onto herbarium sheets. To this day, the smell of formaldehyde in the “Kew Mix” takes me back to the chilly basement space of that collection.
The Kew Herbarium is a massive, internationally important resource for taxonomy, evolutionary biology and ecology, and one which ought to stay where it is, in my opinion.
The purpose of my visits was to exploit the large number of Ceropegia specimens that had been collected by botanists working in Africa, the Middle East, and Asia. These amazing flowers are so complex that they are best preserved in spirit, and that complexity in turn is a function of their sophisticated pollination systems. The flowers temporarily trap their pollinators, releasing them unharmed after a period, during which they will have picked up pollen and/or the flower will have been pollinated. If you have ever grown String-of-Hearts as a house plant, that’s the group we are talking about.
The botanists who collected these flowers were, of course, only interested in the plants. But as well as pickling the blooms they sometimes pickled the insect contents of the flowers, giving us a record of what the flowers were luring into their temporary traps. Not only that, but Ceropegia belongs to the milkweed subfamily of Apocynaceae, which means that their pollen is in the form of pollinia. These are coherent packages of pollen that mechanically, and persistently, clip to the insect. This gives us an opportunity to sort out the real pollinators (with pollinia attached) from other insects that may be inside the flowers for other reasons, such as looking for prey or sheltering from the dry heat of the day.
It had occurred to me that if someone was to check these flowers for insects, and extract any that were found, then we could build up an unprecedentedly complete picture of the diversity of pollinators in a large, mainly tropical plant genus of around 200 species. So that’s what I did, whenever time allowed. Having gained permission to do this, I was pleased to discover that the process was considerably speeded up by the fact that preserving the flowers in this way clears the tissues, making them colourless and translucent. By shining a bench light through the bottles I could see which flowers contained insects and carefully dissect them out.
The work also fed into our large study of pollination systems in Apocynaceae and I even published a small note about an ant specimen that I had extracted which still had the evidence of its last meal (a fly’s wing) protruding from its mouth.
The work at Kew had given us a short cut to understanding how pollination systems have evolved in this big plant species radiation. The equivalent field work required to collect the same data would have taken many person years and no funding agency would have given it the time of day. Not only that, but a portion of the data is from parts of the word that are war-torn, dangerous, and largely inaccessible to field scientists at the moment. Which brings us to the present paper.
All of the pollinators, and most of the flower visitors, to Ceropegia that have been discovered to date are small flies (Diptera) often only a couple of millimetres in length. There are relatively few taxonomists who can identify such flies and most of the specimens I extracted were identified to genus or family by Andrew Whittington. One such specimen was determined to be a species of Lygistorrhina, known as ‘long-beaked fungus gnats‘. It was found in a flower of Ceropegia aristolochioides ssp. deflersiana, which is something of a generalist in this genus of specialists: it’s pollinated by at least four fly genera and 11 others have been collected from its flowers sans pollinia, including this one.
The flower was collected in 1975 by botanist John Wood, in Yemen – like I said, inaccessible – and the semi-arid climate in which it was found, whilst typical for Ceropegia, is unusual for Lygistorrhina. When National Museums Scotland entomologist Vladimir Blagoderov looked at the specimen he quickly realised that it was a new species and contacted Andrew and myself to discuss describing it. The paper documenting the new species, which we have named Lygistorrhina woodi in John’s honour, was published today. Here’s the reference with a link to the paper, which is open access:
A new species of Lygistorrhina (Lygistorrhina) Skuse, 1890, Lygistorrhina woodi sp. nov., is described. The specimen was dissected from an alcohol-preserved flower of Ceropegia aristolochioides ssp. deflersiana Bruyns (Apocynaceae, Asclepiadoideae, Ceropegieae) stored in the Kew herbarium. This is the first occurrence of the lygistorrhine gnats in a hot, semi-arid climate. A key to all known species of the subgenus Lygistorrhina (Lygistorrhina) is provided.
Prof. Jeff Ollerton - ecological scientist and author 