Tag Archives: Science

Key tropical crops at risk from pollinator loss due to climate change and land use – a new study just published

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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:

Millard, J., Outhwaite, C.L., Ceaușu, S., Luísa G. Carvalheiro, da Silva e Silva, F.D., Dicks, L.V., Ollerton, J. & Newbold, T. (2023) Key tropical crops at risk from pollinator loss due to climate change and land use. Science Advances 9, eadh0756

Here’s the abstract:

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.

“Birds & Flowers” book update: here’s the list of chapters!

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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.

Weevily good pollinators – a recent review of a neglected interaction

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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…

That’s not an original joke by any means – it comes from the movie Master and Commander. But it nicely sets up this short post about a review paper that came to my attention earlier in the summer and which fits neatly with my previous post about a special issue of the Journal of Applied Entomology dedicated to the “neglected pollinators”.

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:

Most diverse, most neglected: weevils (Coleoptera: Curculionoidea) are ubiquitous specialized brood-site pollinators of tropical flora

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.

“Enemy release” of invasive plants is unpredictable – a new study just published

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The summer of 2019, before the COVID-19 pandemic turned the world on its head, feels like a very long time ago. Early in that summer, as I recounted on this blog, Zoe Xirocostas joined my research group for a while in order to collect data for her PhD on the comparative ecologies of plants that are native to Europe but invasive in Australia. That work has proven to be very successful, and the latest paper from Zoe’s PhD has just been published.

The paper focuses on the “enemy release hypothesis” (ERH), a well-studied concept in invasion ecology that nonetheless generates significant debate and disagreement. In essence, the ERH posits that the reason why so many species become invasive is that they leave their consumers, pathogens and parasites behind when they move to a new locality. Those “enemies” would normally reduce the fecundity of the invader, putting a brake on their population growth. But in their absence, the invader can become far more successful. Of course, as well as leaving “enemies” behind the invader also loses its “friends”, such as pollinators, seed dispersers, and defensive or nutritional partners. This “Missed Mutualist Hypothesis” is something that I’ve recently explored with Angela Moles, who was Zoe’s main supervisor, and other collaborators in Australia. Expect to hear more about this from Zoe’s work in the near future.

But back to the enemies. Drawing on the most extensive set of standardised comparisons yet collected of the same plants in native and invasive habitats, Zoe found that plants in the invasive populations suffer on average seven times less damage from insect herbivores, as predicted by the (ERH). Rather remarkably, however, the amount of enemy release enjoyed by a plant species was not explained by how long the species had been present in the new range, the extent of that range, or factors such as the temperature, precipitation, humidity and elevation experienced by the native versus invasive populations.

In other words, it’s extremely hard to predict the extent of enemy release based on historical and ecological considerations that one might expect to impose a strong influence.

The study has just appeared in Proceedings of the Royal Society series B and is open access. Here’s the reference with a link to the paper:

Xirocostas, Z.A., Ollerton, J., Tamme, R., Peco, B., Lesieur, V., Slavich, E., Junker, R.R., Pärtel, M., Raghu, S., Uesugi, A., Bonser, S.P., Chiarenza, G.M., Hovenden M.J. & Moles, A.T. (2023) The great escape: patterns of enemy release are not explained by time, space or climate. Proceedings of the Royal Society series B 290: 20231022.

Here’s the abstract:

When a plant is introduced to a new ecosystem it may escape from some of its coevolved herbivores. Reduced herbivore damage, and the ability of introduced plants to allocate resources from defence to growth and reproduction can increase the success of introduced species. This mechanism is known as enemy release and is known to occur in some species and situations, but not in others. Understanding the conditions under which enemy release is most likely to occur is important, as this will help us to identify which species and habitats may be most at risk of invasion. We compared in situ measurements of herbivory on 16 plant species at 12 locations within their native European and introduced Australian ranges to quantify their level of enemy release and understand the relationship between enemy release and time, space and climate. Overall, plants experienced approximately seven times more herbivore damage in their native range than in their introduced range. We found no evidence that enemy release was related to time since introduction, introduced range size, temperature, precipitation, humidity or elevation. From here, we can explore whether traits, such as leaf defences or phylogenetic relatedness to neighbouring plants, are stronger indicators of enemy release across species.

Making plant-pollinator interaction data FAIR – a new draft report just published

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One of the projects in which I’m currently involved is the WorldFAIR project. Funded by the European Commission, WorldFAIR is exploring how to make data FAIR – Findable, Accessible, Interoperable and Reusable – across a range of different disciplines in the sciences and humanities.

My involvement is specifically with Work Package 10, which is focused on data standards for plant-pollinator interactions, particularly as they relate to pollination of agricultural crops. After a year of hard work, I’m delighted to announce that our interim draft report from this Work Package has just been published! You can read the summary and download the report from Zenodo – here’s the link: https://zenodo.org/record/8176978

In addition there’s an associated webinar taking place on August 22nd – more details here: https://worldfair-project.eu/event/rescheduled-worldfair-rdas-10-year-anniversary-the-worldfair-case-study-on-plant-pollinator-interactions-wp10/

There’s more to come over the next twelve months and I’ll post updates as and when they appear. In the meantime, do check out the WorldFAIR website for information about the other Work Packages, their webinar series, FAIR data standards, and so forth.

Should honey bee hives be placed on or near conservation sites?

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Earlier this week, the East Midlands Environment Agency proudly tweeted that they had placed honey bee hives on an ecologically important site that they own. As you might imagine, the response from pollinator experts such as myself, conservation NGOs, and some beekeepers, was not positive, as you can see if you look at the comments beneath my tweet:

By coincidence, overnight I received a message from someone in the USA asking for advice. Here’s a redacted version of their message:

My community has a 4 acre serpentine barren site that is part of a larger string of these unique barrens ….. Honey bee hives have recently been located adjacent to the barrens. Can you advise me as to the best way to determine whether there are, and to document any, adverse effects to the serpentine barrens native pollinators?

The question of how managed honey bees can impact wild pollinators and the pollination of wild plants is one that frequently comes up in the talks and training that I do. Many beekeepers share these concerns – see for example this very detailed blog post by Mark Patterson.

Going back to the question of how to assess any impacts, the simple answer is that it’s not easy and it relies on having good data. This was my response to my American correspondent:

Ideally you would need to take a before-and-after approach where you have data on things like number of native pollinator species, their abundance (including nest sites), rates of visitation of different pollinators to flowers, and fruit or seed set from particular plants. You’d then compare what was going on before the hives arrived with what’s occurring since their arrival.

If you don’t have the “before” data it’s much more difficult to assess if there has been an impact from the honey bees. However, the advice of most conservation groups is to adopt the “precautionary principle” and not site hives on or adjacent to areas of nature conservation value, especially if they are relatively small areas. See for example the Bumblebee Conservation Trust’s advice: https://www.bumblebeeconservation.org/managed-honeybees/

The precautionary principle is a well established concept across a range of areas, including health and engineering, as well as nature conservation. In the latter it needs to be more widely applied, especially when it comes to questions of where to site honey bee hives, and how many.

Plant-based diets are a problem for bees! A new study of the significance of the ratio of food K:Na in bee ecology and evolution

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At the moment Karin and I are in the UK for a couple of weeks. I had work to do as an external examiner at the University of Swansea, plus we wanted to catch up with some family and friends. Our main base has been the home of our mates Ian and Simone and we’ve enjoyed some warm, muggy evenings sitting in their garden chewing the fat. Every now and again my eyes have been drawn to the activities of bumblebees as they move in and out of the foliage of a small Silver Fir. The bees are attracted to the large colonies of an aphid that is feeding on the tree’s trunk, from which they are collecting honeydew, as you can see in the photograph above.

When we think of the diets of bees we automatically think “nectar and pollen”. Honeydew, as a sugar-rich fluid, fits broadly into this concept, though as far as I know there’s been little study of its relative importance as a food source for bees. Aside from a few “vulture bees”, all of the 20,000 or so species are vegetarian. And therein lies a problem. Bees evolved from carnivorous wasps and so the evolution of bees, and their complex ecologies, is tied into this profound dietary shift toward a plant-based diet.

A particular issue that has hardly been investigated until recently is that the ratio of elements within meat is very different to that of plants. In particular, animal tissue has a high ratio of sodium (Na) relative to potassium (K), whereas for plants the ratio is reversed – high ratio of K:Na.

In a new conceptual review paper with my colleagues Zuzanna Filipiak and Michał Filipiak, we have explored the implications of this difference in elemental ratios for bee ecology and evolution, and for the conservation of these important insects. The paper is open access and you can download a copy by following a link in this reference:

Filipiak, Z.M., Ollerton, J. & Filipiak, M. (2023) Uncovering the significance of the ratio of food K:Na in bee ecology and evolution. Ecology e4110. https://doi.org/10.1002/ecy.4110

Here’s the abstract:

Bees provide important ecological services, and many species are threatened globally, yet our knowledge of wild bee ecology and evolution is limited. While evolving from carnivorous ancestors, bees had to develop strategies for coping with limitations imposed on them by a plant-based diet, with nectar providing energy and essential amino acids and pollen as an extraordinary, protein- and lipid-rich food nutritionally similar to animal tissues. Both nectar and pollen display one characteristic common to plants, a high ratio of potassium to sodium (K:Na), potentially leading to bee underdevelopment, health problems, and death. We discuss why and how the ratio of K:Na contributes to bee ecology and evolution and how considering this factor in future studies will provide new knowledge, more accurately depicting the relationship of bees with their environments. Such knowledge is essential for understanding how plants and bees function and interact and is needed to effectively protect wild bees.

That’s a wrap! The manuscript of my next book is with the publisher

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Yesterday I sent the manuscript of my next book Birds & Flowers: An Intimate 50 Million Year Relationship to my publisher, Pelagic. I’d promised the full draft by the end of May, and I did it!

But just as when a movie director says “That’s a wrap” at the end of the final day of filming, the hard work does not stop here. Two people have read the full manuscript as I was producing chapters and their suggestions have been incorporated into this draft. The publisher will now send it to a third, independent beta reader and once their feedback has been acted on it will go to a copy editor who will suggest stylistic changes, check for logic and consistency, and so forth.

At the same time I will be choosing which plates to put in the book, which images to use on the back cover, writing their descriptions and deciding where to cite them; checking the sources and further reading sections for each chapter and formatting the references; and producing an appendix that lists the scientific names against the vernacular names that I am using in the book. I also need to finalise the acknowledgements section.

Once all of that is done, the publisher will type set the book and send me the proofs to check. At the same time as I’m checking those I will construct the index, a process which worked well for my last two books, Pollinators & Pollination: Nature and Society (also for Pelagic) and Plant-Pollinator Interactions: From Specialization to Generalization (which I co-edited with Nick Waser for the University of Chicago Press).

As an author, producing a book is a long process that doesn’t end with the actual writing of the manuscript. It’s incredibly satisfying, however, and working with Pelagic on my second book for them has been a great experience. All being well, Birds & Flowers should be out by early winter.

Now, I have three options for the next book that I’m writing….which one to choose…?

Insect pollination in deep time – a new review just published

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As a teenager one of my main interests was collecting fossils. In search of specimens I wandered for hours, scouring the Carboniferous coal shale heaps and Permian reef outcrops of my native Sunderland. I spent so much time bothering the geology curator at the local museum with my inquiries that he offered to host me for a year as the placement part of my college course. If I had been able to convince my tutors that paleontology was really just biology in deep time I may have ended up as a professional fossil researcher. But it was not to be and instead I spent a (mostly happy) year working in the microbiology laboratory of a local brewery.

My interest in the ecology of the past has never left me, and over the years I’ve contributed a few articles to journals commenting on the latest fossil findings as they relate to pollination and flowering plant evolution. So I was delighted to be asked by Spanish paleontologist David Peris to help with a new review of insect pollination in deep time, led by PhD candidate Constanza Peña-Kairath. That review has just been published in Trends in Ecology & Evolution, and for the next 50 days it’s available for free download by following the link in the reference:

Peña-Kairath, C., Delclòs, X., Álvarez-Parra, S., Peñalver, E., Engel, M.S., Ollerton, J. & Peris, D. (2023) Insect pollination in deep time. Trends in Ecology & Evolution (in press)

Here’s the abstract:

Inferring insect pollination from compression fossils and amber inclusions is difficult because of a lack of consensus on defining an insect pollinator and the challenge of recognizing this ecological relationship in deep time. We propose a conceptual definition for such insects and an operational classification into pollinator or presumed pollinator. Using this approach, we identified 15 insect families that include fossil pollinators and show that pollination relationships have existed since at least the Upper Jurassic (~163 Ma). Insects prior to this can only be classified as presumed pollinators. This gives a more nuanced insight into the origin and evolution of an ecological relationship that is vital to the establishment, composition and conservation of modern terrestrial ecosystems.

Introducing Ceropegia stylesii – a novel species of “Brachystelma” from South Africa

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This is a guest post by Dr Annemarie Heiduk about a new species that she’s recently described.

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In an earlier blog post about the discovery of a novel Ceropegia species, Jeff’s finishing sentence was: “I wonder what else is still waiting to be discovered in the stunning grasslands of South Africa?”

I am happy to provide a first answer to this question: Ceropegia stylesii.

This new species does not have the tubular kettle-trap flowers typical of Ceropegia, which temporarily trap pollinators, but open-rotate corollas where the gynostegium (fused male and female reproductive organs) is freely accessible to pollinators. So, in the traditional sense, C. stylesii is not a Ceropegia. This needs some explanation here!

Ceropegia is a genus in the plant family Apocynaceae (Jeff’s favourite family of plants!) and therein the genus is placed in the subfamily Asclepiadoideae which originally was a family on its own (“Asclepiadaceae”).

Within this subfamily, the genus Ceropegia belongs to the Stapeliinae – a subtribe which comprises ca. 720 species. About 220 species thereof have exciting looking and very cleverly designed kettle-trap flowers which attract small flies as pollinators via deceptive strategies (see http://plantlifesouthafrica.blogspot.com/2019/07/plantlife-sa-volume-473-july-2019.html). The remaining species in Stapeliinae are the well-known stem-succulent stapeliads (ca. 355 species in >30 genera) and ca. 140 species known as Brachystelma.

With increasingly better molecular methods to study the evolutionary relationships of species in Stapeliinae, the traditional grouping of the species was illuminated as being artificial, i.e., species with kettle-trap flowers are not actually a natural group and Brachystelma species are scattered among them; the stapeliads are also nested in Ceropegia but as a single (monophyletic) group. These results based on DNA-sequence similarities are not compatible with the traditional generic concept in Stapeliinae, and as a result, changes were instigated.

Some colleagues wish to see all 720 species of Ceropegia, Brachystelma and the stapeliads merged into one single large genus Ceropegia, a solution which would entail more than 400 new name combinations. Others prefer to adopt a less dramatic change of concept and only include Brachystelma in an enlarged Ceropegia while keeping the stapeliads separate based on their monophyly and distinct vegetative features. This pragmatic solution considers both taxonomic and phylogenetic facts and reduces the previously multiple cases of paraphyly to a single case. More importantly, it avoids hundreds of name changes in the group. Both concepts are correct in their own right and justified, so it is a personal decision which one to follow.

The newly described species C. stylesii would traditionally have been placed in Brachystelma as it is lacking tubular kettle-trap flowers. After the inclusion of Brachystelma into Ceropegia, C. stylesii is placed within section Bowkerianae – a group comprising species both with and without tubular kettle-trap flowers. With the description of C. stylesii, the section now has 15 members of which 10 have open-rotate flowers. Among these, C. stylesii appears to be most closely related to C. gerrardii from which it can only readily be distinguished when in flower (see the lower most image above).

The flowers of C. stylesii superficially look like miniature versions of a dark-flowered form of C. gerrardii, which growths in the same habitat. C. stylesii flowers are only about 6 mm in size whereas those of C. gerrardii are about three times larger. While C. gerrardii occurs in grasslands throughout eastern South Africa, C. stylesii is believed to be endemic to Ngome, where it is known from two localities with a total of less than 10 plants. After the recent discovery of C. heidukiae at Ngome, the area revealed another outstanding member of this amazing plant group, and thereby once again proves its conservation importance.  

C. stylesii is named for David Gordon Alexander Styles, botanical explorer and collector, to honour his valuable contribution to botanical knowledge in South Africa. David is renowned for “…his daring nature to go leaps and bounds for the specimen he is interested in” (see Chetty 2021), a statement I can readily confirm based on personal experience. Many of David’s collections (by now well over 6000 specimens donated to various herbaria) are novelties awaiting to be described. With C. stylesii, a total of five plant species bear his name. I am delighted that eventually a Ceropegia species could be named for him as David’s knowledge on the distribution and habitats of these special plants is of great value to my research on this plant group.