Category Archives: Bees

Rediscovery of a plant species 170 years after it was lost from the Northamptonshire flora


2019-05-23 11.42.26

This past week I’ve been hosting a postgraduate researcher from the University of New South Wales in Australia.  Zoe Xirocostas has been recruited to work on a project on which I’m a collaborating with Prof. Angela Moles and Dr Stephen Bonser (University of New South Wales) and Dr Raghu Sathyamurthy (CSIRO).  It’s funded by the Australian Research Council and will run from 2019-2022.

Zoe’s PhD is about understanding the role of herbivores and pollinators in determining how plant species native to Europe have become invasive in Australia.  She arrived with a wish-list of species that she wants to study at sites in the UK (Northampton), Spain, Estonia, France and Austria, in order to compare them with populations in Australia.  One of those species was small-flowered catchfly (Silene gallica), a plant that I hadn’t seen in Northamptonshire.  The NBN Atlas account for the species shows almost no records for central England and when I checked the Northamptonshire Flora it stated that the species had last been recorded in the county in 1843.  Clearly this was not a plant we could study for this phase of the project.  Or so we thought.

By coincidence, the week of Zoe’s preliminary fieldwork coincided with two days of surveys of the University of Northampton’s new Waterside Campus by staff and students.  This is part of an ongoing project to understand how the development has affected local biodiversity.  Friday was to be the last spring bird survey of the season (see this recent post updating that project) and Thursday was to be devoted to plants and bees.

To help with this we had the assistance of two County Recorders: Ryan Clark for the bees and Brian Laney for the plants, both hugely knowledgeable and enthusiastic about Northamptonshire’s.  We started the surveys on an area of short-cropped, species-rich turf that is being maintained by a combination of rabbit and Canada goose grazing:

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In no time at all Brian had racked up dozens of plant species; it’s really a very rich site indeed.  Bees were fewer and further between, but after an hour we had a list of about 10 species, including one of my favourites, the ashy mining bee:

2019-05-20 15.22.16

Zoe and her field assistant Susmita were busy bagging flower heads for the pollination experiments when suddenly we heard an excited shout from Brian.  He had moved on to look at some plants that were coming up in a disturbed area of ground some distance away.  Unbelievably, Brian had found small-flowered catchfly!  More than 170 years after it had last been record in the county.  On our campus!  We rushed over to take a look, and there it was, near a path that Zoe and I had walked just a couple of days before and completely failed to spot it.  In our defence, although it is striking in close up (see the image at the top of this post) it hides itself very well among other plants:

2019-05-23 11.42.16

An amazing discovery!  But what is this plant doing here?  The answer is that small-flowered catchfly is an annual species of disturbed areas, it requires soil to be turned over in order to allow its seeds to germinate from the soil seed bank.  The construction work on the site has involved moving around hundreds of tons of soil and this has provided ideal conditions for the plant and for many others that are associated with this kind of habitat.  The challenge now will be to work with the university’s estates department to decide on a management plan that involves regular rotovating of that area.  That shouldn’t be too hard, they are as keen to maximise the biodiversity of the campus as we are.

The natural world is full of surprises, especially “lost” species turning up unexpectedly.  Soil seed banks for some species can be very persistent, with seeds remaining dormant for decades or even hundreds of years until conditions are right for germination.  It’s very satisfying to be present at just the right time to see it happen!

To finish here’s a shot of the survey team, minus one member (Vivienne) who had to leave early; from left to right – Ryan, me, Brian, Susmita Aown, Duncan McCollin, Zoe, Janet Jackson:

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Filed under Bees, Biodiversity, University of Northampton, Urban biodiversity

What happens when pollinators lose their flowers? A new study suggests some answers


Biella et al image

Pollinators such as bees and butterflies are highly dependent on flowers to provide nectar as food; at the same time, those plants are reliant on the pollinators for reproduction.  Over the past few decades, declines in both flower and pollinator diversity and abundance have prompted ecologists to wonder about the consequences of flower loss for pollinator communities and for plant pollination.

In a ground breaking new study, a team from institutions in the Czech Republic and the University of Northampton in the UK have published the results of experiments that seek to answer these questions.  Led by PhD researcher Dr Paolo Biella, the team performed experiments in both countries that involved temporarily removing thousands of flower heads from grassland plant communities.  They assessed how the pollinator assemblage responded to their removal, and how effectively the remaining flowers were pollinated.  The team focused on generalist plant species that support the majority of pollinators within a community because these have traditionally been less well studied than highly specialised relationships.

The results are published today in the open access journal Scientific Reports and provide the first demonstration of the ways in which pollinators flexibly adjust their behaviour when faced with a sequential loss of resources.  This flexibility is constrained by the type of flowers they visit, however:  pollinators will tend to switch to flowers of a similar shape to the ones that have been lost.  From the plant’s perspective, things are less clear: the patterns of pollination for the remaining species were idiosyncratic and not as predictable.  Some plants received more pollination during the experiment than before, others less.

For the first time we are seeing the consequences of sudden loss of flowers for both the pollinators and the plants in a habitat.  That the pollinators can respond flexibly to this loss is a welcome indication that these insects might be more resilient to sudden changes than we had thought.  However, the erratic pollination of the flowers shows that there is a great deal of random chance within these ecological systems that is not easily predictable.  In the same week that the UN’s Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) Global Assessment Report on Biodiversity and Ecosystem Services was published, our study reminds us that there is much that we do not currently understand about the consequences of sudden changes in the natural world.

One of the team’s recommendations is that pollination-generalist plant species should be given much more attention in conservation assessments than has previously been the case.  These plants are at the core of plant-pollinator communities and without them the rarer and more specialised species could not exist.

Details of the study are as follows:

Biella P., Akter A., Ollerton J., Tarrant S., Janeček Š., Jersáková J. & Klecka J. (2019) Experimental loss of generalist plants reveals alterations in plant-pollinator interactions and a constrained flexibility of foraging.  Scientific Reports 9: 1-13

Here’s the abstract:

Species extinctions undermine ecosystem functioning, with the loss of a small subset of functionally important species having a disproportionate impact. However, little is known about the effects of species loss on plant-pollinator interactions. We addressed this issue in a field experiment by removing the plant species with the highest visitation frequency, then measuring the impact of plant removal on flower visitation, pollinator effectiveness and insect foraging in several sites. Our results show that total visitation decreased exponentially after removing 1-4 most visited plants, suggesting that these plants could benefit co-occurring ones by maintaining high flower visitor abundances. Although we found large variation among plant species, the redistribution of the pollinator guild affected mostly the other plants with high visitor richness. Also, the plant traits mediated the effect of removal on flower visitation; while visitation of plants which had smaller inflorescences and more sugar per flower increased after removal, flower visitors did not switch between flower shapes and visitation decreased mostly in plants visited by many morpho-species of flower visitors. Together, these results suggest that the potential adaptive foraging was constrained by flower traits. Moreover, pollinator effectiveness fluctuated but was not directly linked to changes of flower visitation. In conclusion, it seems that the loss of generalist plants alters plant-pollinator interactions by decreasing pollinator abundance with implications for pollination and insect foraging. Therefore, generalist plants have high conservation value because they sustain the complex pattern of plant-pollinator interactions.

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Filed under Bees, Biodiversity, Butterflies, Hoverflies, Pollination, University of Northampton, Wasps

Is pollination really an ecosystem service?

Ashy Mining Bee 2017-06-17 10.55.53

Yesterday on Twitter Prof. James Bullock from the Centre for Ecology and Hydrology posted a slightly provocative tweet asking: “why pollination is so often called an ecosystem service. To my mind it is an ecosystem process which can, in some circumstances (e.g. crop pollination), support services such as food provision”.

I confess to being a bit surprised to see this; I’d always referred to pollination (at least by animals) as an ecosystem service, and it’s classified in that way in large status-and-trend reports such as the Millennium Ecosystem Assessment and (more recently) the IPBES Assessment Report on Pollinators, Pollination and Food Production which describes animal pollination as “a regulating ecosystem service that underpins food production and its contribution to gene flows and restoration of ecosystems”.

The crux of James’s question is illustrated in this diagram from a paper by Prof. Georgina Mace and colleagues in 2012 entitled Biodiversity and ecosystem services: a multilayered relationship.  However note that even here, pollination straddles the line between ecosystem processes and services:

Mace ES image

My initial response to James’s tweet was that animal pollination is really a community process as the interaction, and its outcomes, between animal and crop plant is dependent mainly on species diversity and abundance.  Remember, an ecosystem is the sum of the biotic (i.e. community) plus abiotic (e.g. energy, water, mineral nutrients, etc.).  So as far as crop pollination is concerned, the abiotic components of an ecosystem don’t really come into it except in as much as they influence diversity and abundance of all life on Earth.  This is in contrast to more strictly ecosystem processes that link directly to the abiotic factors, such as primary productivity and soil formation, that then support ecosystem services.

It’s further complicated by the fact that many of the plants that perform ecosystem services, such as carbon capture by trees, are themselves dependent upon animal pollination to maintain their populations.  It’s the plants that are providing the ecosystem services but the animals are playing an important role in supporting that.

If you’d like to follow that discussion, which has some interesting contribution from a range of people, here’s the link:


But ultimately I feel that these are fairly arbitrary definitions across a continuum of causes and effects: we know what animal pollination of crops and wild plants is and why it’s important, so what we call it doesn’t really matter, does it?  Other things are much more concerning.  At the moment the UK is experiencing unprecedented weather: for the first time ever, earlier today, a temperature of in excess of 20 Centigrade has been recorded in winter.  It currently feels more like late April or early May than February.  I’m already seeing a lot of pollinator activity in the garden and beyond, and each day more plants come into flower, far earlier than expected.

The current and future effects of such changes in the climate are far more important than discussions of the semantics of processes versus services, however interesting that might be.


Filed under Bees, Biodiversity, Climate change, Ecosystem services, IPBES, Pollination

A poem for Valentine’s Day


I have to confess that I forgot completely about Valentine’s Day, it’s not a celebration that I generally pay much attention to, as expressions of love are something that everyone should be doing all the time, surely?

Anyway, this bastardised version of “Roses are red” is for my wife Karin:

Some bees are red
Others are blue
There’s twenty thousand species
Of every hue

Some flies are yellow
Some wasps are cerise
Many of them pollinate
Better than bees



Filed under Bees, Biodiversity, Poetry, Pollination, Wasps

Recent reviews in pollination biology: an annotated list: UPDATED x 3

2019-02-09 13.47.49

As it’s my birthday today, I thought I’d reward myself by completing a blog post that I started just after Christmas and never got round to finishing.  Review articles that summarise recent developments in a field are an important contribution to the scientific literature that allow us to pause and reflect on where a topic has been and where it is headed.  Having recently (co)authored a couple of reviews I can attest that they are useful in this respect for both the writers and for the readers.

In the past couple of years quite a number of critical and timely reviews have been published which are proving very useful to me: I’m currently writing a book and these reviews have been invaluable in summarising aspects of a field that is currently publishing in excess of 1000 research papers per year. So I thought I’d bring them together into a single listing with a short commentary on each.  No doubt I have missed many other reviews so please feel free to point out any gaps and I will update the list as I go along.

Each review is hot linked to the source; a good proportion of the reviews are open access, notably those from the recent special issue of Annals of Botany devoted to the ecology and evolution of plant reproduction.  Some reviews are very focused, but most are quite broad.  Several of these complement one another.  I hope you find them interesting and useful.

Barrett, S. & Harder, L. (2017) The ecology of mating and its evolutionary consequences in seed plants. Annual Review of Ecology, Evolution and Systematics 48: 135-157

Mating systems, i.e. who breeds with whom, are just as complex in plants as they are in animals.  However some features of seed plants, such as the fact that they don’t move, that most species have both male and female functions, and that their growth is modular and often indeterminate, represent significant challenges that have been overcome in a bewildering variety of ways.


Braun, J. & Lortie, C.J. (2018)  Finding the bees knees: A conceptual framework and systematic review of the mechanisms of pollinator-mediated facilitation.  Perspectives in Plant Ecology, Evolution and Systematics 36: 33-40

In a community, if one plant species positively affects another, we term this “facilitation”.  It can occur at a variety of life stages, including reproduction whereby the presence of one species increase the likelihood of another species being pollinated.  This review shows that it occurs fairly frequently at a variety of spatial scales, but there are still significant gaps in our understanding of the phenomenon.


Fuster, F., Kaiser‐Bunbury, C., Olesen, J.M. & Traveset, A. (2018) Global patterns of the double mutualism phenomenon. Ecography

When species provide benefits to one another in two different ways, for example an animal is both a pollinator and a seed disperser of a plant species, we refer to it as a “double mutualism”.  As this fascinating review shows, double mutualisms are very uncommon, but they are widespread, and probably under-recorded.


Minnaar, C., Anderson, B., de Jager, M.L. & Karron, J.D. (2019) Plant–pollinator interactions along the pathway to paternity. Annals of Botany 123: 225-245 

The male aspect of plant reproduction, i.e. pollen donation, is often neglected when we consider how pollination systems evolve.  This review provides as up to date account of where we are in understanding how paternity influences floral characters such as shape and colour.


Ollerton, J. (2017) Pollinator diversity: distribution, ecological function, and conservation. Annual Review of Ecology, Evolution and Systematics 48: 353-376

A very broad over view of our current understanding of the biodiversity of pollinators, taking a deep time and a wide spatial perspective to put current concerns about loss of pollinators into a wider perspective.


Parachnowitsch, A.L., Manson, J.S. & Sletvold, N. (2019) Evolutionary ecology of nectar. Annals of Botany 123: 247–261 

We often take nectar for granted – it’s just sugar and water, isn’t it?  As this review shows, nectar is dynamic and complex, and affects a range of ecological functions beyond just providing pollinators with a reward.  However there’s still a huge amount we don’t understand about how nectar traits evolve.


Toledo-Hernández, M., Wangera, T.C. & Tscharntke, T. (2017) Neglected pollinators: Can enhanced pollination services improve cocoa yields? A review.  Agriculture, Ecosystems and Environment 247: 137-148

Chocolate is most people’s favourite confectionery and is famously pollinated only by small midges.  Or is it? As this review shows, lots of other insects visit cocoa flowers, but their role as pollinators has not been well studied.


Vizentin-Bugoni J, PKM Maruyama, CS Souza, J Ollerton, AR Rech, M Sazima. (2018) Plant-pollinator networks in the tropics: a review. pp 73-91 In Dáttilo W & V. Rico-Gray. Ecological networks in the Tropics. Springer.

This book chapter that I co-authored with some very energetic and creative young Brazilian researchers summarises what’s currently known about plant-pollinator interaction networks in tropical communities.  One of the conclusions is that they are really not so different to those in temperate and subtropical biomes.


Wright, G.A., Nicolson, S.W. & Shafir, S. (2018) Nutritional Physiology and Ecology of Honey Bees. Annual Review Entomology 63:327-344

A review of how bees use nectar and pollen at the level of both the individual and the colony, focused on the most widespread of pollinator species.


As expected, several people have told me about reviews I’d missed, and in some cases ones that I had read but forgotten about!  I’ll list them below, though without annotations:

Bennett, J. et al. (2018) A review of European studies on pollination networks and pollen limitation, and a case study designed to fill in a gap, AoB Plants 10:

Knight, T. et al. (2018) Reflections on, and visions for, the changing field of pollination ecology. Ecology Letters 21: 1282-1295

Vallejo-Marin, M. (2018) Buzz pollination: studying bee vibrations on flowers. New Phytologist



I had deliberately restricted the reviews to 2017 onwards, but via email David Inouye kindly sent a few older ones through which are equally useful:

Brosi, B. J. (2016) Pollinator specialization: from the individual to the community. New Phytologist: 210: 1190–1194

Hahn, M. and C. A. Brühl (2016) The secret pollinators: an overview of moth pollination with a focus on Europe and North America. Arthropod-Plant Interactions: 1-8

Inouye, D. W., et al. (2015) Flies and flowers III: Ecology of foraging and pollination. Journal of Pollination Ecology 16



A more recent addition to this set of reviews was sent to me by Anne-Laure Jacquemart.  Although it’s focused just on one (rather variable) crop, I think it will be really useful for anyone interested in the pollination biology of crop plants:

Ouvrard, P. & Jacquemart, A.-L. (2019) Review of methods to investigate pollinator dependency in oilseed rape (Brassica napus).  Field Crops Research 231: 18-29





Filed under Bees, Biodiversity, Brazil, Honey bees, Mutualism, Pollination

Pollinator availability, mating system and variation in flower morphology in a tropical savanna tree – a new, open-access study

Curatella image by Pedro Lorenzo

Widespread plant species can encounter a variety of different pollinators across their distributional range.  This in turn can result in local adaptation of flowers to particular pollinators, or to an absence of pollinators that results in adaptations for more self pollination.   A newly published study by one of my former PhD students, André Rodrigo Rech in Brazil, has looked at this in the widespread South American savanna tree Curatella americana.  André studied 10 populations separated in space by thousands of kilometres, in cerrado vegetation, one of the most threatened habitat types in Brazil.  Here’s the abstract:

Widely distributed organisms face different ecological scenarios throughout their range, which can potentially lead to micro-evolutionary differentiation at specific localities. Mating systems of animal pollinated plants are supposed to evolve in response to the availability of local pollinators, with consequent changes in flower morphology. We tested the relationship among pollination , mating system, and flower morphology over a large spatial scale in Brazilian savannas using the tree Curatella americana (Dilleniaceae). We compared fruit set with and without pollinators in the field, and analyzed pollen tube growth from self- and cross-pollinated flowers in different populations. Populations with higher natural fruit set also had lower fruit set in bagged flowers, suggesting stronger barriers to self-fertilization. Furthermore, higher levels of autogamy in field experiments were associated with more pollen tubes reaching ovules in self-pollinated flowers. Morphometric studies of floral and leaf traits indicate closer-set reproductive organs, larger stigmas and smaller anthers in populations with more autogamy. We show that the spatial variation in mating system, flower morphology and pollination previously described for herbs also applies to long-lived, perennial tropical trees, thus reemphasizing that mating systems are a population-based attribute that vary according to the ecological scenario where the plants occur

Here’s the full citation with a link to the paper which is open access:

Rech, A.R., Ré Jorge, L., Ollerton, J. & Sazima, M. (2018) Pollinator availability, mating system and variation in flower morphology in a tropical savannah tree. Acta Botanica Brasilica (in press)

The illustration of Curatella americana  and its pollinators is by Pedro Lorenzo.

This paper is a contribution to a special issue of Acta Botanica Brasilica dedicated to floral biology and pollination biology in Brazil It’s all open access and if you follow that link you can download the papers.

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Filed under Bees, Biodiversity, Biogeography, Brazil, Evolution, Pollination

Why I’m joining the People’s Walk for Wildlife on Saturday 22nd September

Peoples walk for wildlife

If you live in the UK and have an interest in wildlife you’ve probably heard about the event that takes place in London this coming Saturday:  The People’s Walk for Wildlife.  If you follow that link you’ll find a video of Chris Packham explaining what the walk is all about and why he’s organised it, plus logistical information, timings, etc.

Karin and I are going to join the walk and I thought I’d give a brief summary of why I think it’s important for people to take part.

If you watch the video you’ll see that Chris does a great job of laying out the issue of wildlife loss, a loss not just of species but of abundance.  There are species that still can be found in Britain but which have declined in numbers by 90% or more over my lifetime.  Such species can be found in all of the major groups of biodiversity in this country:  birds, mammals, fish, reptiles and amphibians, insects and other invertebrates, fungi, and plants.  Many, many millions of individuals gone from our countryside.

Why has this happened?  Well, the causes are complex and inter-related.  Agricultural intensification over the last century has been a major issue as I’ve previously discussed on this blog in relation to pollinator extinctions.  But that’s only part of it. Another big problem that we have in the UK is an unwillingness to let nature just get on with itself.  We feel that we have to manage everything: Too many ravens?  Cull them.  Hedgerows or road verges looking a bit untidy?  Cut them.  Old tree infected with a fungus?  Chop it down.

In part this mindset is linked to an idea of what natural heritage should look like, an idea of order within a landscape, of making the countryside look pretty, and of doing things simply because that’s what our predecessors did.  A good example was recently tweeted by Dave Goulson who had found mole traps on a Natural Trust property that he visited; as Dave rightly said:  “When will we stop slaughtering harmless wildlife that causes us the tiniest inconvenience?”  There is no reason in this day and age to kill moles – what conceivable harm do they do?  In fact, as ecosystem engineers, they are an important part of the ecology of the British countryside.

One of the reasons why this is happening largely unnoticed by the government agencies responsible for the environment is that our landscapes change at a very slow rate.  Indeed places like the Lake District or the Scottish Highlands or the Chiltern Hills look much the same as they have done for hundreds of years.  Visually they are still stunning places to visit and that’s why they attract millions of tourists every year, and also why people enjoy living there.  But they have lost much of their wildlife and, with it, some of the ecological function that makes them work as ecosystems.  If this continues then natural processes such as dispersal of seeds by birds and mammals, and the subsequent maintenance of tree populations, will cease.

But that’s okay isn’t it?  Trees and shrubs not establishing themselves: go out and plant them by hand.  Is this really what we want?  If it is then we will end up turning our countryside into a museum.  And not even a very good museum at that: not a museum with dynamic interactive displays, rather a static, dull set of exhibits that you can only peer at through dusty glass.

So that’s why we are joining the People’s Walk for Wildlife next Saturday: this is an important issue and people need to show government that they are concerned.  I hope you agree and I hope you will join us.

Dave G. has promised to come dressed as a bumblebee; I’ve seen his costume and he’s a man of his word, so it’ll be worth looking out for him.  I can’t promise anything so flamboyant but I may well take a placard that says something like:  “Save ALL of our pollinators, not just bees!”  If you spot it, do some over and say hello.


Filed under Bees, Biodiversity, Ecosystem services

There ain’t no b(ee) in Starbucks


I do love a road trip.  Karin and I are just back from a drive too and from her homeland of Denmark, via ferry from Harwich to Hook of Holland, in order to pick up a porcelain dinner service that belonged to her grandparents.  It was a great trip and I hope to put up some photos from that shortly.  But before then I thought I’d write a short post about a key element of any good road trip:  coffee.

If I drive for two hours or so I have to take a break and top up with at least a coffee, possibly also a snack, certainly lunch at the appropriate time.  Last Friday, en route to Harwich, we stopped off at a motorway service station that had a Starbucks.  Whilst waiting for my coffee (Americano, no milk, thank you very much) I noticed that there was quite a lot of text on the walls all about where and how coffee grows, its cultivation and harvesting, and so forth.  Being the sort of ecologist who is interested in how plants flower and set fruit I focused on the relevant text (see the photo above).  It’s a little indistinct but, in essence, this is what it says:

“Coffee plants flower once a year…..the flowers are jasmine scented….and then some magic happens….and nine months later you get coffee fruit”

Okay, I made up the bit about “magic” but, seriously, that’s what is implied by this text: that by some hocus pocus, coffee flowers turn into the coffee fruit that contain the beans.  No mention made of the fact that pollinators (mainly wild and managed bees) are important in this process.  Although coffee can self pollinate (which is fairly magical I suppose) without the pollinators we would have much less coffee of poorer quality.

In my recent review of pollinator diversity and conservation I did some back-of-the-envelope calculations of coffee production to illustrate the dependence of modern human society on animal pollination. Here’s what I wrote:

“Coffee is pollinated by a range of wild insects (mainly bees) and managed honeybees (Ngo et al. 2011), is second only to oil in terms of its value as a commodity [turns out this is not true – see below*], and supports millions of subsistence farmers. Global coffee production in 2016 amounted to 151.624 million bags, each weighing 60kg (International Coffee Organisation 2017). One coffee bean is the product of a single fertilisation event following the deposition of at least one pollen grain on a flower’s stigma. The mean weight of a single coffee bean is about 0.1g which means there are approximately 600,000 beans in a 60kg bag. The total number of coffee beans produced in 2016 is therefore 151.624 million bags multiplied by 600,000 beans per bag, which equals 90,974,400,000,000, or >90 trillion coffee beans. However coffee is on average 50% self pollinating (Klein et al. 2003) and a single bee visit may pollinate both ovules in each coffee flower, so we can divide that figure by four: nonetheless global coffee production requires at least 22 trillion pollinator visits to flowers. Clearly the global coffee market is supported by many billions of bees that require semi-natural habitat as well as coffee plantations in order to survive”.

I don’t want to pick on Starbucks, it just so happens that that’s where we stopped, and I have certainly seen similar displays in Costa, for instance, with again no mention of bees.  Apparently Starbucks et al. don’t want to acknowledge the role of these bees in supporting their (very lucrative) industry, at least not in the cafes themselves.  If you Google “Starbucks pollinators” then you find some information online about how the company values bees, etc. etc.  But come on coffee sellers, you’re better than this, let the public know in the places where the public goes!  If you need advice from an expert, someone to write some text for you, I’m more than happy to act as a consultant.


*Even careful scientists get things wrong sometimes – this is a myth as you can read if you follow this link.



International Coffee Organisation. 2017. Coffee production statistics for 2016. Accessed 20th June 2017

Klein AM, Steffan-Dewenter I, Tscharntke T. 2003. Fruit set of highland coffee increases with the diversity of pollinating bees. Proc. R. Soc. B. 270: 955–961

Ngo HT, Mojica AC, Packer L. 2007. Coffee plant – pollinator interactions: a review. Can. J. Zool. 89:647–660



Filed under Bees, Biodiversity, Ecosystem services, Honey bees, Pollination

British phenological records indicate high diversity and extinction rates among late-summer-flying pollinators – a recently published study

Balfour et al Figure 1

Natural history records of plant flowering and pollinator foraging, much of them collected by well informed amateurs, have huge scientific importance. One of the values of such records to ecology is that it allows us to document where these species occur in space and when they are active in time. This can be done at a range of spatial and temporal scales, but large-scale patterns (for example at a country level) are, I think, especially useful because they provide scientific evidence that can inform national conservation strategies.

During 2017 I collaborated with a young early career researcher at the University of Sussex, Dr Nick Balfour, on an analysis of the phenologies of British pollinators and insect pollinated plants.  That study was recently published (see citation below) and I think that the results are fascinating.

Nick did most of the leg work on this, which involved assessing more than one million records that document the activity times of aculeate wasps, bees, butterflies and hoverflies held in the databases by three of the UK’s main insect recording organisations, the Bees, Wasps and Ants Recording Society (BWARS), the UK Butterfly Monitoring Scheme (UKBMS) and the Hoverfly Recording Scheme (HRS).  Information on flowering times was taken from a standard British flora (Clapham et al. 1990 – Flora of the British Isles. Cambridge University Press).

As well as looking at annual flight periods and flowering trends for these organisms we also focused on pollinator and plant species that were endangered or extinct. Here are some headline results and thoughts on what the work shows:

  • About two-thirds (62%) of pollinator species peak in their flight times in the late summer (July and August), though there was some variation between the different groups – see the figure from the paper above).  Particularly noticeable was the double peak of the bees, with the first peak denoting the activity of many early-emerging solitary bees, such as species of the genus Andrena, whilst the second peak is other solitary bees plus of course the bumblebees which by that time have built up their colonies.
  • A rather fixed phenological pattern with respect to different types of plants was also apparent, which I was not expecting at all: insect pollinated trees tend to flower first, followed by shrubs, then herbaceous species (again, refer to the figure above). This might be because larger plants such as trees and shrubs can store more resources from the previous year that will give them a head start in flowering the following year, but that idea needs testing.
  • Putting those first two points together, what it means is that trees tend to be pollinated by those earlier emerging bees and hoverflies, whereas the herbs are mainly pollinated by species that are active later.
  • When looking at the extinct and endangered pollinators, the large majority of them (83%) were species with a peak flight times in the late summer, a much larger proportion than would be expected given that 62% of all species are active at that time. However this was mainly influenced by extinct bee species and the same pattern was not observed in other groups.
  • The obvious explanation for that last point is that historical changes in land use have led to a dramatic reduction in late summer flowering herbaceous species and the subsequent loss of floral resources has been highly detrimental to those bees. But intriguingly no such pattern was apparent for the endangered pollinators and clearly there are complex reasons why pollinators should become rare or extinct, a point that I have discussed previously on the blog.
  • The lack of late summer flowering resources for pollinators is a contentious issue however as plant conservation groups have in the past recommend that meadows and road verges are cut in late summer to maximise plant species richness.  Mowing road verges once or twice a year certainly benefits plant diversity, as this recent review by Jakobsson et al. (2018) demonstrates.  But there’s very little data available that assesses how timing of cutting can affect pollinators.  The only study that I know of (and if I’ve missed any, please let me know) that has considered this is the PhD work of one of my former students, Dr Sam Tarrant who looked at pollinators and plants on restored landfill sites compared to nearby nature reserves.  In a paper that we published in the journal Restoration Ecology in 2012 we showed that on restored landfill sites the abundance of pollinators in autumn surveys (conducted September-October) was just as high as for summer surveys.  On nature reserves, which are routinely cut from mid-July onward, this was not the case.

Here’s the full citation of Nick’s study with a link to the publisher’s website, and a copy of the abstract is below.  If anyone wants a PDF, drop me a line:

Balfour, N., Ollerton, J., Castellanos, M.C., Ratnieks, F.L.W. (2018) British phenological records indicate high diversity and extinction rates among late-summer-flying pollinators. Biological Conservation 222: 278-283


The long-term decline of wild and managed insect pollinators is a threat to both agricultural output and biodiversity, and has been linked to decreasing floral resources. Further insight into the temporal relationships of pollinators and their flowering partners is required to inform conservation efforts. Here we examined the
phenology of British: (i) pollinator activity; (ii) insect-pollinated plant flowering; and (iii) extinct and endangered pollinator and plant species. Over 1 million records were collated from the historical databases of three British insect monitoring organisations, a global biodiversity database and an authoritative text covering the national flora. Almost two-thirds (62%) of pollinator species have peak flight observations during late-summer
(July and August). This was the case across three of the groups studied: aculeate wasps (71% of species), bees (60%), and butterflies (72%), the exception being hoverflies (49%). When species geographical range (a proxy for abundance) was accounted for, a clear late-summer peak was clear across all groups. By contrast, there is marked temporal partitioning in the flowering of the major plant groups: insect-pollinated tree species blossoming predominantly during May (74%), shrubs in June (69%), and herbs in July (83%). There was a positive correlation between the number of pollinator species on the wing and the richness of both flowering insect pollinated herbs and trees/shrubs species, per calendar month. In addition, significantly greater extinctions occurred in late-summer-flying pollinator species than expected (83% of extinct species vs. 62% of all species). This trend was driven primarily by bee extinctions (80% vs. 60%) and was not apparent in other groups. We contend that this is principally due to declines in late-summer resource supplies, which are almost entirely provisioned by herbs, a consequence of historical land-use change. We hypothesize that the seasonality of interspecific competition and the blooming of trees and mass-flowering crops may have partially buffered spring flying pollinators from the impacts of historical change.


Filed under Bees, Biodiversity, Butterflies, Hoverflies, Macroecology, Pollination, Wasps

Pollinators, landscape and friends: our recent trip to the Danish island of Sejerø

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This is not the first time I’ve written about the beautiful Danish island of Sejerø – see my post “Why do bumblebees follow ferries?“.  It’s home to our friends Pia and Stephen Valentine (Stephen is the very talented artist who produced the fabulous study of waxwings that Karin commissioned for my birthday last year).  Earlier this month we traveled over to stay with them and to explore some more of the island.  Here are some photos and thoughts from that trip.

Despite the hot, dry weather that northern Europe has been experiencing recently there were pollinators aplenty.  Thistles and knapweeds (both groups from the daisy family Asteraceae) are well known to be drought tolerant and attract a lot of insect interest.  This is a Pantaloon Bee (Dasypoda sp.)  If it was Britain I’d say that it was D. hirtipes, but there are other species on the continent so I can’t be sure.  These bees are well named: the “pantaloons” are found only on the females and are used to collect pollen, especially from Asteraceae.

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I believe that this is the male of this species; note the absence of the pollen-collecting hairs on the rear legs and the yellow face, typical of many male bees:

The flower heads of the knapweeds were highly sought after; on this one, two different bumblebees (Bombus spp.) were competing with two Silver Y moths (Autographa gamma):

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Sometimes the bumblebees got an inflorescence to themselves, though the photobombing Silver Ys were never far away:

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It’s been a good year for the Silver Y, large numbers have migrated northwards from southern Europe and we’ve had lots in our garden too.  On Sejerø they were everywhere, on all kinds of plants: 

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The butterfly is one of the Blues (Lycaenidae), possibly Common Blue (Polyommatus icarus), but again this being Denmark they may have other species that I’m not familiar with.  Note the Silver Y photobombing once more…:


Wild carrot (Daucus carota) was common on the island and always attracts a wide range of flies, wasps and beetles:


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Close to home we found a huge cherry tree laden with the fruits of pollination and collected a couple of kilos for Stephen to make into jam.  Stoning them was messy but fun and a nice opportunity to sit and chat about nature and people:

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I was very impressed with Stephen’s up-cycled general purpose baskets, made from plastic containers he finds on the beach, wire, and lengths of old hosepipe:

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Along the shore another edible plant, Sea Kale (Crambe maritima) was attracting a lot of attention from white butterflies (Pieridae) whose caterpillars feed on this and other members of the cabbage family (Brassicaceae):

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I tried a piece of raw leaf; it tasted ok, salty and a little bitter.  Apparently it’s very nice if you blanch the young leaves.  It’s a distinctive and impressive component of the beach flora:

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Amidst the greens, buffs and browns of the beach landscape we encountered the occasional scarlet of a patch of poppies (Papaver sp.):

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Everywhere on the island we saw evidence of the link between life on land and in the sea, and the cycles and processes upon which that life depends.  Sand martins (Riparia riparia – an apt name – “riparian” refers to the interface between land and water) are common and their nest excavations speed up the return of sediments back to the sea:

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Favoured rocks have been used by gulls and other sea birds for generations, their guano helping to enrich these coastal waters and fueling the primary production of seaweeds and diatoms, which in turn feed other shore life:

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Evidence of human activities was never far away, though, concrete and steel blending with nature:

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Wheat fields merging with the sky:

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Thanks to Pia and Stephen, and of course Zenja, for making this such a wonderful trip and allowing us to join them in exploring their home island:

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Filed under Bees, Biodiversity, Birds, Butterflies, Moths, Pollination