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

Is there really a “battle for the soul of biodiversity” going on at IPBES? UPDATED x 2

Carved demon

No.  But perhaps I should give some context to both question and answer…

The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) describes itself as “the intergovernmental body which assesses the state of biodiversity and of the ecosystem services it provides to society, in response to requests from decision makers”.   Sounds a little dry, I agree, but in fact IPBES is the most exciting and innovative international environmental body to have emerged in recent years.  Exciting because its remit is specifically to assess how society is affecting global biodiversity in toto, but also its value to humans.  Innovative because it’s a broad church that is trying to bring together the knowledge and expertise of both natural and social scientists, practitioners, indigenous peoples, and stakeholders of all kinds. This broad approach is something which some other international bodies have not, traditionally, been so keen to adopt.

IPBES has its critics who see it as superfluous in that its mission overlaps too much with that of organisations such as the Convention on Biological Diversity, the Ecosystem Services Partnership, and the United Nations Environment Programme.  However I certainly think that there’s room for such an organisation.  We need as many voices as possible shouting about how important these issues are, at all levels of society, from the work of local conservation volunteers and the People’s Walk for Wildlife upwards to the highest levels of international governance.  So I’m a supporter of what IPBES is trying to do; perhaps I’m biased but I was especially impressed by the fact that the first major output of IPBES was a badly needed Assessment Report on Pollinators, Pollination and Food Production for which I acted as an expert peer reviewer over its two iterations.  I’ve written posts about this a couple of times – see for example this one.

In recent weeks, however, there’s been some reports of in-fighting within IPBES, and between IPBES and other organisations, that science journalists have seen as being a major war of ideas.  It culminated in Nature publishing a piece entitled “The battle for the soul of biodiversity“, backed up by an editorial suggesting that “the global body for biodiversity science and policy must heal rifts“.

The crux of the perceived disagreements centre on terminology and concepts as much as anything, and specifically the notion of ‘ecosystem services’ versus ‘nature’s contributions to people”.  These seem to me to be saying much the same thing using different words, and I have to say that I was shocked when I read those articles and wondered what the hell was going on: was IPBES really falling apart before it had even managed to firmly establish itself (remember it only launched in 2013)?  Or was this just journalistic hyperbole of the kind that serves no real purpose other than to increase sales and page views?

I have no inside track to IPBES’s workings so I kept an eye on developments.  I was delighted, therefore, to see the 19th September issue of Nature publish four letters from IPBES insiders and experts from other organisations.  All of these, plus the articles I linked to above, are open access.

The first letter is from Jasper Montana of Sheffield University pointing out that “ideas need time to mature” and that “debates are grist to the mill of innovation for environmental governance”.  In other words, IPBES is a young organisation and the sorts of terminology being used are far from mature: terms such as “ecosystem services” and “natural capital” are at most a few decades old.  Clearly there is an urgency in building governance systems that can effectively conserve biodiversity, but debates around the best terms to use will not hinder that process.

The second letter from Bernardo Strassburg in Brazil entitled “honour guidelines that reconcile world views” pointed out that IPBES’s own guide to such concepts notes that the ecosystem services approach is just one of several, all perfectly valid, ways of viewing the relationships between people and nature, and of seeing people as part of nature.

The next letter is from IPBES chair Sir Bob Watson assuring us that “squabbles don’t obscure the bigger picture” and that a diversity of opinions and ideas is one of IPBES’s strengths.  It’s worth noting here that the original model for IPBES was the IPCC (Intergovernmental Panel on Climate Change) which has in the past been criticised for not allowing a diversity of opinions among contributors to its reports.  You can’t please all the people all of the time, and clearly not Nature journalists….

Finally Rudolf de Groot, chair of the Ecosystem Services Partnership, plus colleagues Pavan Sukhdev & Mark Gough, argued that “sparring makes us strong” and write the most critical of the four letters, stating that they “strongly object to the tone and content” of the original article.  They assure us that the Ecosystem Services Partnership and IPBES are not in competition and that there is mutual respect for different opinions and concepts.  Furthermore “both organizations…stand united against biodiversity loss and ecosystem degradation…. Irrespective of the terminology used, our community is undivided in our knowledge that we fundamentally depend on nature in countless ways.”

So there you have it.  The Nature article and editorial were, in my opinion and those of the letter writers, over the top, exaggerating debates and disagreements that, whilst certainly real, do not endanger IPBES nor its mission.  I urge you to read the original articles then the letters, and make up your own mind.  Comments welcome as always.

UPDATE 1:  Just after I tweeted this post the Natural Capital Coalition added it to the bottom of a tweet thread that they had started when the original articles were published.  I confess that I missed these first time round but the thread adds extra detail to why the articles were misleading.  Well worth reading – here’s the start of the thread:

 

UPDATE 2:  It seems Nature is happy to continue the exchange of views following the article; the current issue of the journal contains another letter (once again open access), this time from Jim Harris (Cranfield University) and Janne S. Kotiah (University of Jyväskylä, Finland) pointing out that “the debate around which framework to use to value biodiversity could stem from the relatively recent coining and adoption of the concept of nature’s contribution to people (NCP).  Google Scholar returns only 19 hits for NCP and nearly 100,000 for ecosystem services, mainly because the latter has been in use for much longer“.

They go on to say (as all the correspondents on this article have) that they see no reason why the two worldviews of NCP and ecosystem services are irreconcilable. NCP seems new and different because it’s unfamiliar jargon   All of this reminded me of one of my first posts on this blog – “Business and biodiversity: oil and water?” which documented an event that I attended in London called “Biodiversity & ecosystem services: new collaboration opportunities for academics with businesses” .  It’s worth quoting what I said with regard to jargon within the field:

“In the workshop I attended there was some discussion as to whether technical language such as “biodiversity”, “natural capital” and “ecosystem services” (which one contributor referred to as “eco-babble”) deters senior business managers from engaging with nature conservation. I pointed out that words and phrases such as “email”, “internet” and “world wide web” were not so very long ago similarly considered to be technical jargon but are now part of our every day language.”

I still stand by this: technical language is only a barrier to engagement if people do not take the time to understand the jargon.  And jargon can become everyday language very swiftly.

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The good and the bad in biodiversity

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At some point last week a small fly bit my leg, perhaps a biting midge in the family Ceratopogonidae*.   In doing so, the fly infected the wound with bacteria, possibly a Staphylococcus species.  That’s turned into a large, painful cellulitis (pictured) that is causing fever, body aches, dizziness, sweating, sleep problems, exhaustion, and general unwellness**.  Although I love biodiversity, sometimes it causes all kinds of health problems for humans.  Bad biodiversity.

A visit to my GP yesterday afternoon resulted in her prescribing me a course of antibiotics, specifically clarithromycin.  Although this is a synthetic antibiotic it was developed as a variant of erythromycin which in turn is a natural antibiotic isolated from the bacterium Streptomyces erythraea.  Good biodiversity.

There’s a temptation in environmentalism to see nature as all good, a Mother Earth that provides for us.  Which it does, and one way of considering these benefits is as ecosystem services.  However nature also inflicts a whole range of ecosystem disservices on the human population of this planet, backed up by some of its biodiversity.  Nature is neither all good nor all bad, it just is.

My first year undergraduate classes start next week with the module Biodiversity: an Introduction.  I hope to be well enough to teach it and at some point I’ll use this as an example the good and the bad in biodiversity.

 

 

*Ironically flies in this family are major pollinators of one of the main groups of plants I study in the genus Ceropegiasee this post from last year.

**And a pain in the arse to my wife – sorry Karin!  It was she who persuaded me to go and see the GP after a few days of “no, no, it will get better on its own….”

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Hornets are pollinators too!

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This morning I spent a very pleasant couple of hours walking around the farm that’s at the heart of the Warner Edwards Gin Distillery, in Harrington just north of Northampton.  We are setting up some collaborations around conservation and sustainability between the university and Warner Edwards.  The first of these involves surveys of their farm by one of our final year undergraduates, Ellie West, to assess pollinator diversity and abundance, and opportunities for habitat enhancement on the farm.

One of the highlights of this morning’s visit was seeing this gorgeous hornet (Vespa crabro) taking nectar from common ivy (Hedera helix).  I think that she’s a queen stocking up on energy prior to hibernating.  But just look at how much pollen she’s carrying!  There’s every chance that she’s a very effective pollinator of ivy, which is a key nectar resource at this time of year.  It’s such an important plant in other ways too: ivy binds the landscape physically and ecologically, in ways few other native plants do.  Pollination by insects such as hornets (and hundreds of other species) results in berries that are eaten by birds and mammals, whilst the branches and dense, evergreen canopy provides nesting sites for birds and shelter for over wintering insects.

Hornets and ivy: two of my favourite native British species.

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Filed under Biodiversity, Birds, Mammals, Pollination, University of Northampton, Wasps

Which h index should I use? UPDATED

2018-09-16 10.04.28

UPDATE:  Thanks to my kind commentators (below) who pointed out that one can change Google Scholar, taking out papers that don’t belong, merging variants, etc.  It had been a while since I looked at Google Scholar and perhaps I knew this in the past but had forgotten.  However I had an issue with it linking to my Google account and so had to delete the old profile and set up a new one.  That seems to have worked OK, I have got rid of the publications that weren’t mine, and my h-index looks to be fairly accurate at 38.  I have adjusted the text below to reflect this.

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Despite some (well founded) criticism as to its usefulness, the h-index seems to be with us to stay.  In a couple of posts I’ve articulated some of its advantages and disadvantages – see for example What’s the point of the h-index? and How does a scientist’s h-index change over time? – and it’s clear that more and more funding agencies are using it to evaluate the track record of applicants.  Just this afternoon I finished the second of a couple of grant reviews in which the applicant was asked to state their h-index.  What they were not asked was which h-index they should state, i.e. the source of the value, though I think that this is important information.  Why?  Because it varies so much depending on where the it comes from.  I’ll give you an example – here’s my own h-index values taken from a few different sources:

Google Scholar: h = 38

ResearchGate: h = 36

ResearchGate (excluding self citations): h = 34

Web of Science (all databases): h = 34

Web of Science (Core Collection): h = 29

Scopus: h = 29

There’s a 10 point difference (almost 25%) between the largest and the smallest values.  So which one should I cite in grant applications, on my CV, etc.  Well the largest one, obviously!  Right?  Well maybe, but not necessarily.  In fact none of these values are completely accurate, though some are more accurate than others.

Web of Science includes papers and book chapters that don’t belong to me, and I can easily shave a couple of points off that value.  Some of these mis-attributions are chapters from a volume that I co-edited.  Some are papers that I edited for PLoS ONE and which have been assigned to my record.  Others are for the two or three other researchers named “J. Ollerton” who are out there.  Google Scholar had some entries which are just bizarre, such as “The social life of musical instruments” by Eliot Bates, which Google Scholar seems to think I wrote and has credited me with its 102 citations.  However, as you can see form the update, I’ve corrected this.

Web of Science and Scopus don’t pick up as many citations in books or reports as does Google Scholar which is a deficiency in my opinion.  Being cited in a peer-reviewed journal is often thought of as being the gold standard of citation but frankly I’m very happy to be cited in government and NGO reports, policy documents, etc., which themselves may often be peer reviewed, just by a different type of peer.

Poised in the middle of this range, ResearchGate may be most accurate but it lacks transparency: as far as I can see there isn’t a way to look at all of your citation data per paper in one go, you have to look at each publication individually (and who has time for that, frankly?)

As far as calculating an accurate h-index is concerned I don’t think we will ever come to an agreement as to what should be considered a publication or a citation.  But systems like Google Scholar and Web of Science should at least try to be accurate when assigning publications to an individual’s record.

So which h-index should you use?  In the interests of accuracy and honesty I think it’s best to state a range and/or add a proviso that you have corrected the value for mis-attribution of publications.  In my case I’d say something like:

“Depending on source my h-index lies between 29 (Scopus) and 38 (Google Scholar)”.

If the h-index is to have any value at all (and there are those who argue that it doesn’t and shouldn’t) then it requires us as scholars to at least try to make it as accurate as we can.  Because frankly I don’t think it’s going to go away any time soon.

 

 

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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.

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There ain’t no b(ee) in Starbucks

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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, 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.

References

International Coffee Organisation. 2017. Coffee production statistics for 2016. http://www.ico.org/prices/po-production.pdf 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

 

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

The evolution of pollination systems in one of the largest plant families: a new study just published – download it for free

Figure 1 JUNE revision

Interactions between flowering plants and the animals that pollinate them are known to be responsible for part of the tremendous diversity of the angiosperms, currently thought to number at least 350,000 species.  But the diversity of different types of pollination system (bird, bee, moth, fly, etc.) is unknown for most large, related groups of plants (what systematists term “clades”) such as families and subfamilies.  In addition we know little about how these interactions with pollinators have evolved over time and in different parts of the world.  Only a handful of groups of flowering plants have been studied with respect to questions such as:

How much do we currently know about the diversity of pollination systems in large clades?

How is that diversity partitioned between the smaller clades (e.g. subfamilies, tribes, genera) of a family, and what are the evolutionary transitions between the major groups of pollinators?

Do these pollination systems vary biogeographically across the clade’s range?

These sorts of questions have been addressed for the massive, globally distributed Apocynaceae (one of the top 10 or 11 largest angiosperm families with more than 5,300 species) in a study just published using a new database of pollinators of the family.  What’s more, the work is open access and anyone can download a copy for free.  Here’s the citation with a link to the paper:

Ollerton, J., Liede-Schumann, S., Endress, M E., Meve, U. et al. [75 authors in all] (2018) The diversity and evolution of pollination systems in large plant clades: Apocynaceae as a case study. Annals of Botany (in press)

In this study we have shown that (among other things):

  • The family is characterised by an enormous diversity of pollination systems involving almost all of the major pollen vectors and some that are nearly unique to the Apocynaceae.
  • Earlier diverging clades have a narrower range of pollination systems than those that evolved later.
  • Transitions from one type of pollination system to another are evolutionarily constrained, and rarely or never occur, whereas others have taken place much more often, e.g. between wasp and beetle pollination.
  • There is significant convergent evolution of pollination systems, especially fly and moth pollination, by geographically and phylogenetically distinct clades.

You’ll notice that there are 75 (!) authors on this paper.  That’s because we’ve pulled together a huge amount of previously unpublished data and used some state of the art analyses to produce this work.  It was a monumental effort, especially considering that my colleague Sigrid Liede-Schumann and I only decided to push ahead with this project about a year ago when we chatted at the International Botanical Congress that I posted about at the timeIn truth however the origins of this paper go back over 20 years to 1997 when when Sigrid and I published a study of what was then known about pollination systems in the Asclepiadaceae (the asclepiads).

In that paper we said that the research “is intended to be ongoing…[we]…hope to re-review asclepiad pollination within the next decade”.  At the time I didn’t think it would actually take more than 20 years!  However over that period a lot has changed.  For one thing the Asclepiadaceae no longer exists, broken up and subsumed within a much larger Apocynaceae.  Also, I’ve done a lot of work in the field and in the herbarium on some of the smaller groups within the family, such as CeropegiaOthers, including many of my co-authors, have also been working on different groups in various parts of the world.  Finally the level of sophistication of the analyses we are now able to do has increased beyond recognition compared to what we could achieve in the mid-1990s.  All of this means that now is the right time to produce this study.

Having said all of that, this is still a work in progress.  Our Pollinators of Apocynaceae Database contains a sample of just over 10% of the species in the family.  So lots more data on plant-pollinator interactions needs to be collected before we say we fully understand how pollination systems have evolved in this most remarkable family.  I’d be happy to talk with anyone who is interested in the family and being involved in future data collection.

The database will be freely available to anyone who wants to use it – lots more can be done with this information and, once again, I’m happy to chat with potential collaborators.

I was recently interviewed about the study, and about plant-pollinator interactions and the Apocynaceae more generally, for the In Defense of Plants podcast – here’s a link to that interview.

Finally, I’d like to express my sincerest thanks to my co-authors on this study – I really couldn’t have done it without you guys!

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Filed under Apocynaceae, Biodiversity, Biogeography, Evolution, Pollination, Wasps

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

Abstract:

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.

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

A once in a lifetime sunset?

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It’s been a curious year in the UK, weather wise, with an early, mild spring interspersed by sudden cold snaps that may (or may not) have had a profound impact on pollinators, and then a summer that was hotter and drier than any in living memory.  There’s been some amazing thunderstorms and torrential rains, and weeks when there was no rain at all.  Then, on Thursday evening, as Karin and I were coming back from a walk around Abington Park (via a quick stop in the pub) the heavy, rain-bloated skies conspired with the setting sun to produce, for a brief period, a display of light and clouds that was more vibrant and gorgeous than any I’ve ever seen.  The sky reflecting from the rain-soaked pavements of Northampton added further drama to what may well be a once in a lifetime experience.

Here are a few shots I managed to take using the camera on my phone; I’ve not altered the colour or played with images in any way, but they do partial justice to the quality of the light that evening.

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Filed under Biodiversity, Climate change