Some seaweeds have “pollinators”! New research published this week

Most of us have at some time stared in fascination at the life contained within the pools that form on rocky shores at low tide. But none of us realized that a whole new class of ecological interaction was taking place!

The 12,000 or so described (and many un-named) seaweeds are incredibly important organisms. Their diverse and abundant photosynthesizing fronds make them one of the main primary producers in coastal seas, creating food and habitat for a huge range of animals. Not only that, but some – the coralline seaweeds – lock up vast amount of CO2 as calcium carbonate and help to create reef systems in the same way as coral.

Although scientists have studied seaweeds for hundreds of years, many aspects of their ecology are still unknown. Their detailed mode of reproduction, for example has only been studied in a small proportion of species.

In a newly published study in the journal Science, French PhD researcher Emma Lavaut and her colleagues have shown that small isopod crustaceans – relatives of woodlice and sea slaters – facilitate the movement of the equivalent of seaweed sperm (termed “spermatia”) from male to female reproductive structures in just the same way that bees and other pollinators move pollen between flowers, so fertilizing female gametes.

Your read that correctly: some seaweeds have pollinators!

It’s an incredible finding! And the implications of this are enormous: Emma and her colleagues have added a whole new branch of life to the examples of sedentary (fixed-place) organisms that require a third party to enable their reproduction. In addition to being a fascinating biological discovery, it has significant environmental and sustainability implications.  

Seaweeds are a diverse group of macroalgae that appeared more than one billion years ago, at least 500 million years before the evolution of what we think of as “true” plants, such as the flowering plants, conifers, cycads, ferns and mosses. Sexual reproduction in the brown and green seaweeds, which include kelps, wracks and sea lettuces, involves spermatia that are mobile and use a flagellum to swim through the water to seek out female reproductive structures. However, Emma studied a seaweed, Gracilaria gracilis, which belongs to the Rhodophyta or red seaweeds, and none of the species in this group have these swimming sperm equivalents.

Sexual reproduction in the red seaweeds has therefore always been something of a mystery. Three quarters of species have separate male and female individuals and so they cannot mate with themselves. It was assumed that the gametes were just released into water currents that haphazardly transported them to the female reproductive organs, much as wind pollinated grasses and pine trees release their vast clouds of pollen on land. The authors of this new study, however, point out that most sexual reproduction by these red seaweeds takes place in the relatively still waters of rock pools, a habitat that they mimicked in the laboratory in a series of elegant aquarium experiments.

The isopod crustaceans are attracted to the seaweed because they provide a habitat away from predators and a supply of food: they graze on the microalgae that colonise the seaweed’s fronds. Picking up spermatia and moving them between fronds is a side-effect of this activity by the small invertebrates. As you can see from the illustration above, the isopods and the seaweed are engaged in a “double mutualism“: a plus sign (+) indicates a positive effect of one species on another, while a minus sign (-) indicates a negative impact. 

What I find especially fascinating about this research is that both the seaweed (Gracilaria gracilis) and the isopod (Idotea balthica) were originally described as species more than 200 years ago. They also have an extremely wide distribution. The isopod is found around the coasts of Europe and down the eastern seaboard of the Americas. The seaweed is pretty much found globally. These are not rare, unusual species, yet the interaction between them has only just been discovered! This is a point that I made in my recent book Pollinators & Pollination: Nature and Society: quite often, species that are well known interact in previously undocumented ways because no one has had the time or inspiration to look closely at them.

Although the idea that small sea creatures might be helping seaweeds to reproduce sounds very fanciful, there is a precedence for this discovery. Back in 2016, in a paper published in Nature Communications, a group of Mexican researchers led by Brigitta van Tussenbroek showed that a species of seagrass is pollinated by a diverse assemblage of small crustaceans and polychaete worms. Seagrasses are flowering plants, not seaweeds, but clearly this type of mutually beneficial relationship can exist between different species in the oceans.

Rhodophyta are the most diverse group of seaweeds, with more than 7,000 known species. They are especially abundant on coastal shores, oceanic habitats that are under huge pressure from infrastructure development, pollution, and climate change. At the same time, these seaweeds are economically important and millions of tonnes of them are collected every year as food, as nutritional and pharmaceutical supplements, and to produce agar. In order to conserve these seaweed populations, we need to better understand their ecology and their environmental requirements.

The work by Emma Lavaut and colleagues suggests that interactions with their “pollinators” may be a critical aspect of this understanding. In the same way that “Save the Bees” has been a rallying call for conserving interactions between species on land, we may soon hear this message echoed in “Save the Isopods”. At the very least, I have to add a new section to the second edition of my book!

Full disclosure: I was one of the reviewers of the original manuscript submitted to Science by Emma and her co-authors. It’s a rare privilege to review a study and think: “Wow! This is a game-changer!” and including this paper it’s happened to me only a handful of times. The editors at Science kindly invited my colleague Dr Zong-Xin Ren and myself to write a Perspective piece about the work and we were delighted to do so.

Image credits: Isopod and diatom images from Lavaut et al (2022). Gracilaria image by Emoody26 at English Wikipedia CC BY 3.0 Design by Shijia Wen and Jeff Ollerton.

Pollinator-flower interactions in gardens during the COVID-19 pandemic lockdown of 2020: the data paper has just been published!

During the lockdown period of the COVID-19 pandemic in 2020, many pollination ecologists were stuck at home: universities and research institutes were closed and restrictions on travel meant that it was not possible to get out and do field work. In order to keep active and motivated, and to turn adversity into an opportunity, an ad hoc network of more than 70 researchers from 15 different countries (see the map above) decided to collect standardised data on the plant-pollinator networks in their own gardens and nearby public spaces.

When combined with information about location, size of garden, floral diversity, how the garden is managed, and so forth, this would provide some useful data about how gardens support pollinators. For those with kids at home it could also be a good way of getting them out into fresh air and giving them something to do!

Following discussions, several different protocols were instigated which depended upon the time available to the researchers, including one that mirrored the UK Pollinator Monitoring Scheme’s  FIT (Flower-Insect Timed) counts.

The resulting data set of almost 47,000 visits by insects and birds to flowers, as well as information about flowers that were never visited, is freely available and will be an invaluable resource for pollination ecologists. For example, analysing the links between ornamental flowers that share pollinators with fruits and vegetables such as apples and beans, will allow us to make recommendations for the best plants to grow in home gardens that can increase yields of crops.  

There’s an old saying about turning adversity into a positive outcome: “When life gives you lemons, make lemonade”, and the researchers were pleased to find that there’s one record of Citrus limon in the data set!

The paper describing the data set has just been published in the Journal of Pollination Ecology and you can download a PDF of the paper and the associated data for free by following this link.

Sincere thanks to all of my co-authors for their commitment to the project!

Which honeybees are declining and which are not?

Over the weekend there was a discussion on Twitter about “beewashing” that was spun out of this tweet by London beekeeper Richard Glassborow. Richard and his colleagues are some of the most responsible beekeepers that I know and they are getting increasingly frustrated by claims from irresponsible companies that keeping a hive of bees in your garden will help to “save the bees”, backed up by spurious claims that “honeybee colonies are dying out”.

The Twitter exchange prompted me to produce the Condescending Wonka meme that you see above because, as I discussed in my recent book Pollinators & Pollination: Nature and Society, pollinator conservation is a really complex area. But there’s no doubt that beekeeping as it’s being widely promoted is not the answer to bee conservation. Let me explain why.

The word “honeybee” does not refer to just one species. It’s most often* applied to bees in the genus Apis, especially the Western Honeybee Apis mellifera, but there are another seven or so Apis species to which the word can be applied. Of those other Apis species, most have never been domesticated and they live as free-living colonies is the various parts of Asia where they evolved. Only Apis cerana is kept in hives, as far as I am aware. The conservation status of most of these other Apis species is unclear but given that they are predominantly forest species, and deforestation is a chronic problem in Asia, we can surmise that some species may be declining. If you want to know more about them the Wikipedia page is a good starting point.

In this short post I just want to consider the Western Honeybee (Apis mellifera). This is a really knotty species to get to grips with because there are multiple subspecies and within subspecies there are various genetic lineages. In addition, the Western Honeybee has been subject to artificial selection for desirable qualities, such as docility, amount of honey produced per hive, and disease resistance, as well as cross-breeding between different subspecies**. The best recent summary of our current understanding of Western Honeybee genetics and conservation is this 2019 review by Fabrice Requier and colleagues, from which I’ve drawn quite a bit of information.

For the purposes of this explaining what’s going on, it’s easiest to think about the species as comprising three “megapopulations”:

Western Honeybees that are managed in hives: For the most part these are not endangered. Britain has as many hives now as it did in the mid-1950s and indeed globally we have more hives than ever (about 90 million hives at the last count). They are found far beyond their natural range and have been introduced into places where they are not native such as the Americas, parts of Asia, and Australia. STATUS: doing just fine.

Western Honeybees that have founded “feral” colonies: These have escaped from hives in countries where they have been introduced and become naturalised. They are doing well, too well in fact: they are a significant conservation issue in places like Australia. STATUS: doing just fine.

Western Honeybees that are living wild in their native range: This is where things become a little muddier. The African populations of the various subspecies seem to be doing well, but more studies are needed to confirm this. In Europe, actually defining what constitutes “wild” honeybees across a region where a lot of selection and hybridization has gone on, probably for thousands of years, is tricky. However there’s no doubt that wild colonies of Apis mellifera are not uncommon in suitable woodland: see this paper about free-living colonies in Ireland by Keith Browne and colleagues, for instance. Note their statement that genetic evidence shows that “the free-living population sampled is largely comprised of pure A. m. mellifera“, i.e. the European Black Honeybee. STATUS: probably doing quite well though more data is needed.

Conclusion: as I said, it’s really complicated and I don’t pretend to have all of the answers, no one does. But what IS clear is that managed Western Honeybees are not declining and keeping yet more hives of them is not going to help us to “Save the Bees”. I’ll leave the last word to Requier et al., whose review I really do recommend: “We argue for the redirection of attention from managed honey bees to the neglected conservation of wild honey bees.” Amen to that.


*The term “honeybee” is sometimes also used for other social bees that produce honey, for example stingless honeybees in the genus Trigona, but there’s no real consensus on what “honey” actually is, and as I’ve argued in another post, bumblebees (Bombus spp.) also produce honey.

**You may be horrified (but perhaps not surprised) to learn that in the 1930s the Nazis enacted policies to ensure that German beekeepers kept only European Black Honeybees (Apis mellifera mellifera), in line with their views on racial “purity”. Then in the early 1940s, German beekeepers suffered a huge number of colony losses due to disease. The restrictions were lifted to allow beekeepers to cross their bees with disease-resistant A. mellifera carnica. Go figure.

Have honey bees declined in Britain? An update of the numbers

If you’ve read my book Pollinators & Pollination: Nature and Society you’ll know that I have a section in the chapter “The shifting fates of pollinators” that deals with the honey bee situation. In that section I bring together the most comprehensive data set so far available on changes in number of hives in Britain. It’s based on a couple of earlier blog posts and if you’ve not read my book take a look at this one first and then this one to give you some context and more information about the sources of the data.

So far this year I have had several requests from people for the original data (which I’m happy to supply) and queries about what it means. So I thought that the time was right to update the graph with the latest official government figures from BeeBase.

The graph above brings the story up to 2021 where the official estimated number of hives is 272,631. That’s an increase of more than 40% since the first BeeBase estimate in 2015.

The take home from this figure is that the current number of honey bee hives in Britain is similar to what it was in the mid-1950s.

So the answer to the question “have honey bees declined in Britain?” is a resounding NO! They are at least as abundant as they were almost 70 years ago. This reflects the global situation where there’s been a substantial increase in hive numbers since the 1960s, as you can see in the figure below.

So if you want to “Save the Bees” or otherwise support pollinators, please focus on the wild, unmanaged species rather than the managed Western Honeybee (Apis mellifera). As always, comments and questions are welcome below or send me a message via my Contact page.

Published today: a new children’s book about bees and other pollinators!

One of the projects with which I’ve been involved over the last year has been advising on a new book for children about bees and other pollinators, called Can We Really Help The Bees? Written by Katie Daynes and wonderfully illustrated by Róisín Hahessy, it tells the story of what happens when a swarm of bees comes to the window to let a group of children know that they, and their friends the other pollinators, are in trouble. Can they help? Yes they can!

It’s been a real pleasure working with Katie and Róisín on this project for Usborne Publishing and seeing the ideas, text, and illustrations evolve over time. I’ve written a short post over at the Usborne blog with some ideas about how to get children involved in helping the pollinators, and I think that it’s worth repeating one of the things that I wrote: everyone can make a difference to the wildlife around us and no one is too young to be involved!

Because of my involvement with Can We Really Help The Bees? I wasn’t able to include it on my curated list of the best books about bees and other pollinators at the Shepherd site. But it definitely should be on there and is highly recommended!

Pollinators (not) on the menu at Kew

Recently Phil Stevenson and I advised on an art/science project called Minus Pollinators which considered what a small café menu might look like if there were no pollinators to help produce the many, many fruits and vegetables and nuts that are animal pollinated.

The project is a collaboration between writer and consultant Max Fraser and artist Freddie Yauner. To quote Freddie’s description on his website, the project represents:

A dystopian future in the form of a drinks kiosk where the staples such as coffee, teas, juices, chocolate etc. are no longer available due to pollinator decline…the mobile drinks kiosk acts as an exhibition display, with artworks painted in pollen…and a take-away pamphlet…detailing the importance of insect pollinators for our collective future on this planet.

Minus Pollinators was commissioned as part of a summer-long event called Food Forever at the Royal Botanic Gardens, Kew, after which it goes to the Groundswell festival.

It was a pleasure to work with Max, Freddie and Phil on this because art/science projects are a great way of getting the message across about the importance of biodiversity and the current environmental crisis that we are facing.

How can the European Rail Network support biodiversity? A new report just published

Rail travel is my favourite form of transport and always has been. I like its slower pace and the fact that on a long journey you can sit back, read or work, and watch the landscape unfold. Not only that but it’s one of the most environmentally friendly types of mass transport. So when I was asked to be one of the lead authors on a report outlining how the European Rail Network can support biodiversity along its 230,000 km length, I was happy to be involved! And that’s one of the main projects that I’ve been working on over the past 12 months, during which I’ve researched the literature, written and revised drafts, and learned a huge amount about the ecology of the rail network!

The report, which was formally released yesterday, was commissioned by the International Union of Railways (Union Internationale des Chemins de Fer or UIC), founded in 1922 as the global industry body for rail transport. The writing and desk top research was led by the UK Centre for Ecology and Hydrology (CEH).

If you follow the link you can find out more about the European Railways: Strategies and Actions for Biodiversity report and download a PDF copy.

That’s not the end of my involvement, however: the next stage is a technical guide and I’m already starting to work on that. I will report back once it’s complete.

Tracking trends in Neotropical pollinators: how good is our understanding and is more data always better?

In my recent book Pollinators & Pollination: Nature and Society I discussed the current state of our knowledge of how populations of pollinators have changed over time. Although we have some quite detailed data for particular, often charismatic, species or for certain geographic localities or regions, for most species we know almost nothing. As I wrote in the chapter “The shifting fates of pollinators”:

“For most pollinators we are ‘data deficient’, in other words, we don’t know how their populations are performing. They could be doing well, but they may not be”

This is particularly true for those regions for the world that hold the greatest terrestrial biodiversity: the tropics. For the vast majority of species in the tropics we know precious little about trends in their populations and how their distributions have changed over time in the face of wide-scale land transformation and recent climatic shifts. Filling in some of the gaps in our knowledge of Neotropical pollinator distributions is one of its aims of SURPASS2, a collaboration between South American and UK ecologists, and one of several research and outreach projects with which I’m involved.

In a new study that’s come out of that work, led by Rob Boyd from the UK Centre for Ecology and Hydrology, we’ve used the GBIF database to look at the changing distributions of four important groups of pollinators: bees, hoverflies, leaf-nosed bats and hummingbirds. In particular we were interested in understanding the kinds of biases that come with such publicly available data, and whether recent efforts to add data to GBIF has improved our understanding of trends.

Our overall conclusion is that there are significant limitations and biases inherent in all of these data sets even for groups like hummingbirds which one would imagine are well documented by scientists and bird-watching naturalists. In addition, having more data does not necessarily help matters: it can introduce its own biases.

The paper is open access and feely available; here’s the reference with a link:

Boyd, R. J., Aizen, M.A., Barahona-Segovia, R.M., Flores-Prado, L., Fontúrbel, F.E., Francoy, T.M., Lopez-Aliste, M., Martinez, L., Morales, C.L., Ollerton, J., Pescott, O.L., Powney, G.D., Saraiva, A.M., Schmucki, R., Zattara, E.E., & Carvell, C. (2022) Inferring trends in pollinator distributions across the Neotropics from publicly available data remains challenging despite mobilization efforts. Diversity and Distributions (in press)

Here’s the abstract:

Aggregated species occurrence data are increasingly accessible through public databases for the analysis of temporal trends in the geographic distributions of species. However, biases in these data present challenges for statistical inference. We assessed potential biases in data available through GBIF on the occurrences of four flower-visiting taxa: bees (Anthophila), hoverflies (Syrphidae), leaf-nosed bats (Phyllostomidae) and hummingbirds (Trochilidae). We also assessed whether and to what extent data mobilization efforts improved our ability to estimate trends in species’ distributions.

The Neotropics.

We used five data-driven heuristics to screen the data for potential geographic, temporal and taxonomic biases. We began with a continental-scale assessment of the data for all four taxa. We then identified two recent data mobilization efforts (2021) that drastically increased the quantity of records of bees collected in Chile available through GBIF. We compared the dataset before and after the addition of these new records in terms of their biases and estimated trends in species’ distributions.

We found evidence of potential sampling biases for all taxa. The addition of newly-mobilized records of bees in Chile decreased some biases but introduced others. Despite increasing the quantity of data for bees in Chile sixfold, estimates of trends in species’ distributions derived using the postmobilization dataset were broadly similar to what would have been estimated before their introduction, albeit more precise.

Main conclusions
Our results highlight the challenges associated with drawing robust inferences about trends in species’ distributions using publicly available data. Mobilizing historic records will not always enable trend estimation because more data do not necessarily equal less bias. Analysts should carefully assess their data before conducting analyses: this might enable the estimation of more robust trends and help to identify strategies for effective data mobilization. Our study also reinforces the need for targeted monitoring of pollinators worldwide.


SURPASS2 has been a hugely productive project as you’ll see if you look at the Publications page of the website. There’s much more to come and I’ll report on those research papers as they appear.

Common Elder: a natural and cultural history – new article just published

Common Elder (Sambucus nigra) is a plant that has fascinated me since my childhood, when I spent many happy hours scrambling around in its branches and pelting friends with the small fruits that stained our clothes and skin. I was therefore delighted to be able to finally write about my fascination in an article in the May issue of British Wildlife magazine. Although many dismiss it as a rather weedy, commonplace plant, I hope that readers are pleasantly surprised by just how interesting Common Elder is, in terms of its utilitarian value, the mythology and superstitions associated with it, and of course the wildlife that it supports.

I’m developing a talk based on this article, which I’m happy to present online for any natural history or botanical groups. If it’s of interest, drop me a line via my Contact page.

Watch my recent interview on Earth To Be

Recently I enjoyed chatting with Dr Daniela Scaccabarozzi for the YouTube channel that she runs called Earth To Be. In a wide ranging interview we discussed my recent book, how it came about, some of the things that intrigued me during its research (including a cockroach-pollinated flower!), and the role of people and pollinators in the wider ecosystem. Thanks to Daniela for the invitation to chat! Here’s the link to the interview.