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.
PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) is one of the most important sources of data for large-scale modelling of how changes in land use is impacting biodiversity. Marry that with future climate models and you have a powerful tool for understanding how these two major factors in global change will shape both biodiversity and human society over the coming decades.
In recent years it’s been a privilege to be part of a project led by Joe Millard and Tim Newbold that’s using PREDICTS to model how pollinators and pollination services are likely to be impacted by human activities. The first paper from that work (which was Joe’s PhD) was entitled ‘Global effects of land-use intensity on local pollinator biodiversity’ and came out in 2021, as I documented on my blog at the time.
Yesterday a second paper was published, this time focused on how land use and anthropogenic climate change interact to potentially affect insect-pollinated crops across the world.
Our main finding is that it’s tropical crops, especially cocoa, mango, watermelon, and coffee, that in the future will suffer the greatest negative impacts from loss of pollinators. Although we can have perfectly healthy diets without consuming any of those, they currently support tens of millions of farmers across the tropics and are part of global supply chains worth billions of dollars per year.
Here’s the full reference with a link to the paper, which is open access:
Insect pollinator biodiversity is changing rapidly, with potential consequences for the provision of crop pollination. However, the role of land use–climate interactions in pollinator biodiversity changes, as well as consequent economic effects via changes in crop pollination, remains poorly understood. We present a global assessment of the interactive effects of climate change and land use on pollinator abundance and richness and predictions of the risk to crop pollination from the inferred changes. Using a dataset containing 2673 sites and 3080 insect pollinator species, we show that the interactive combination of agriculture and climate change is associated with large reductions in insect pollinators. As a result, it is expected that the tropics will experience the greatest risk to crop production from pollinator losses. Localized risk is highest and predicted to increase most rapidly, in regions of sub-Saharan Africa, northern South America, and Southeast Asia. Via pollinator loss alone, climate change and agricultural land use could be a risk to human well-being.
Biodiversity Net Gain (or BNG) promises to transform the way that we approach nature conservation in the UK. I’ve been giving a lot of thought to what this might mean for insect pollinators and have produced a new report that summarises the opportunities that BNG presents and how we can make the most of them. You can download a copy of that report by following this link.
This is meant to be a working document and as BNG progresses, and our understanding of its impacts on pollinators increases, I will update it. In the meantime, please do feel free to comment.
‘…people would need to be very weak in the head… before it would occur to them to go into the garden and eat snails…’
Anon. (1867)
Delighted to announce that my essay “A short history of snail-eating in Britain” will be in October’s issue of British Wildlifemagazine. This is a topic that’s intrigued me for many years because it has a close connection to the snail-eating habits of folks (my own family included) in the area of the north-east of England where I grew up. Hopefully it will also interest, and surprise, the readers of British Wildlife!
Today I returned the final, edited files of the book manuscript to the publisher. It’s been a long summer of ‘fine distinctions and nice judgements’, to quote my editor, the inimitable Hugh Brazier. Now that’s all finalised, I thought that it was time to share the chapter titles with you – here goes:
Introduction: Encounters with birds and flowers
1 Origins of a partnership
Understanding 50 million years of bird and flower evolution
2 Surprising variety
The astounding diversity of pollinating birds
3 Keeping it in the family
Accounts of the different groups of bird pollinators
4 A flower’s point of view
How many plants are bird-pollinated, and where are they found?
5 In the eye of the beholder
What do bird flowers look like?
6 Goods and services
The enticements given to birds for pollinating flowers
7 Misaligned interests
The ongoing conflicts between flowers and birds
8 Senses and sensitivities
How bird brains shape the flowers that they pollinate
9 Codependent connections
Networks of interacting flowers and birds
10 Hitchhikers, drunks and killers
The other actors in the network and how they affect the main players
11 The limits to specialisation
How ‘specialised’ are the relationships between birds and flowers?
12 Islands in the sea, islands in the sky
Isolation, in oceans or in mountains, results in some remarkable interactions
13 The curious case of Europe
Why did we believe that Europe had no bird-pollinated flowers?
14 ‘After the Manner of Bees’
The origins of our understanding of birds as pollinators, and their cultural associations
15 Feathers and fruits
Birds as pollinators of edible wild plants and domesticated crops
16 Urban flowers for urban birds
Bird pollination in cities and gardens
17 Bad birds and feral flowers
The impact of invasive species
18 What escapes the eye
The decline and extinction of bird–flower relationships
19 The restoration of hope
People as conservationists of birds and their flowers
There you have it! I’m incredibly excited that the book is now just about finished (I still have to proof read the typeset text and produce an index) and I look forward to finally having a copy in my hands. Birds & Flowers: An Intimate 50 Million Year Relationship is available for pre-order from Pelagic Publishing, or via online bookshops.
A pollination ecologist was recently working on the reproduction of a tropical plant species and discovered that the flowers were visited by two species of weevils, one large and one small.
The larger weevil was too big to access the nectar from the front, so it chewed its way into the flowers, destroying the petals, and in the process picking up no pollen.
The other weevil species was, however, able to enter the flowers, where it became smeared with pollen, which it then transferred to the stigmas in flowers of other plants.
The pollination ecologist therefore concluded that the true pollinator of this plant was, indeed, the lesser of the two weevils…
Writing in the open access Peer Community Journal, Julien Haran, Gael Kergoat, and Bruno de Medeiros have produced a really fascinating review of weevil pollination called:
Weevils are beetles, members of the superfamily Curculionoidea, which contains an estimated 97,000 species. Many are herbivores, including seed predators – I first encountered them as a researcher during my PhD when I assessed the impact of one species as a seed predator of my study plant Bird’s-foot Trefoil. Surprisingly, however, pollinating relationships have evolved multiple times between weevils and plants. Drawing on published studies and their own unpublished observations, the authors conclude that such “associations have been described or indicated in no less than 600 instances.” Most of these are brood-site pollination systems that have probably evolved from seed predation relationships.
No doubt many more examples of weevil pollination remain to be discovered but as it stands, this review paper is a great summary of a fascinating and still rather neglected corner of pollination ecology.
Prof. Jeff Ollerton - ecological scientist and author 