Category Archives: Biodiversity

Pesticides and pollinators: some new studies and contrasting conclusions

The question of whether or not neonicotinoid pesticides are negatively impacting agricultural pollinator abundance, diversity and behaviour continues to focus the minds of researchers. It’s an issue that has been almost constantly in the news since the earliest suggestions that these pesticides were harming pollinators. These concerns have led to temporary EU restrictions on the use of these chemicals, a decision that was partially over turned this year in the UK.

The past two months has seen the publication of at least five papers on the topic, two of them this week alone. In this post I want to highlight those papers and provide some commentary.

The first two studies have shown that neonicotinoid pesticides can affect pollinator behaviour, and specifically the memories of both honey bees and bumblebees:

Wright et al. “Low doses of neonicotinoid pesticides in food rewards impair short-term olfactory memory in foraging-age honeybees”

Stanley et al. “Bumblebee learning and memory is impaired by chronic exposure to a neonicotinoid pesticide“.

Subtle behavioural changes such as those documented here are not generally assessed in standard toxicological safety assessments for pesticides, which are mainly focused on whether or not the chemicals kill non-target animals, and at what dosage. But for plant-pollinator interactions (including agricultural pollination) such changes in pollinator behaviour could be crucial to the effectiveness of the pollinators. How crucial? Well up until today we didn’t know; but with the publication of another paper by Stanley and colleagues we now have evidence that the sub-lethal effects on pollinator behaviour can actually translate into an effect on pollination of apple crops:

Stanley et al. “Neonicotinoid pesticide exposure impairs crop pollination services provided by bumblebees“.

The study is the first one to my knowledge that tests the effects of field-relevant doses of pesticides on pollinator performance and subsequent pollination services in a commercial farm crop, and adds some valuable hard data to an already heated debate. The story, embargoed until this evening, has already been picked up by media, including the BBC News website.

To summarise the study: using artificial bumblebee colonies and caged apple trees Stanley and colleagues implemented an experiment in which they tested the effect of two different levels of exposure to a neonicotinoid pesticide on pollinator behaviour and subsequent pollination services to the fruit trees. They found a clear effect of exposure to the higher level of pesticide, resulting in a change in bee behaviour and a subsequent reduction in apple quality.

By way of a contrast, another study this week has focused on the lethal effects of these pesticides. Henry et al. “Reconciling laboratory and field assessments of neonicotinoid toxicity to honeybees” has shown that although the chemicals are lethal to individual honey bees, the overall impact of the loss of the bees is buffered by the fact that the colonies can simply produce more worker bees to compensate for the losses. This is interesting but needs to be judged in the context of the fact that honey bees are very unusual and atypical compared to most other pollinators, and indeed most other bees. They produce very, very large colonies with a unique social structure, and so this compensation might be expected. These caveats were echoed by some of the scientists asked to comment on the study in media stories such as the one on the BBC News website.

Finally, Godfray et al. have updated their earlier review of the environmental effects of these pesticides with “A restatement of recent advances in the natural science evidence base concerning neonicotinoid insecticides and insect pollinators“. Given the rate at which new studies are coming out, it won’t be long before a second restatement is required!

Where does this leave the whole debate around pesticides? Still with firmly entrenched views on both sides I would have imagined. No doubt the debate will run and run.

Meanwhile, important as it is, the focus on pesticides is in danger of over-shadowing other really interesting studies that might affect how we manage our agro-ecosystems in the UK. For example, I’d completely missed a paper from the end of September by Pywell et al. entitled “Wildlife-friendly farming increases crop yield: evidence for ecological intensification“. As far as I can judge from the Altmetric information for the paper, so too had the media: it received no coverage on any of the usual outlets. But this is important stuff that deserves wider publicity: it’s going to take more than a ban on pesticides to recover some of the biodiversity (at both a species and a habitat level) that we’ve lost due to intensive farming over the last 100 years or so.

Pollination syndromes: a brief update on recent developments, and news that Stefan Vogel has passed away

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In a recent post I discussed the current debates about “pollination syndromes”, which I described as “sets of flower characteristics that have repeatedly evolved in different plant families due to the convergent selection pressures applied by some groups of pollinators”.

The authors of the Ecology Letters paper that I discussed (Rosas-Guerrero et al. 2014) have now replied to our original critique of their approach and you can read that reply (Aguilar et al. 2015) in Journal of Pollination Ecology by following this link. Readers can make up their own minds as to whether the authors have responded adequately to our concerns, but I just briefly wanted to raise three points.

The first is that much of these authors’ response is focused on an earlier paper of ours (Ollerton et al. 2009) rather than on our critique per se. Nick Waser, Mary Price and myself have therefore written a second response that deals with some of the misunderstandings apparent in that piece; it’s available to download here.

The second point relates to the existing literature on pollination syndromes and pollinator effectiveness used by Rosas-Guerrero et al. (2014); as we demonstrated in our critique this is clearly a biased data set that is skewed towards groups of plants with relatively large flowers, “interesting” pollination systems, and text book examples of classical pollination syndromes such as bird and bat pollination. Researchers who study flowers and their pollinators choose their subjects based on a whole set of criteria, but random selection is not one of them. However as far as we can judge, Aguilar et al. (2015) seem to be arguing that drawing strong, “universal” conclusions about syndromes from this highly biased data set is perfectly acceptable because of the statistical rigour of formal meta-analysis. I’d re-iterate our main point that no amount of statistical rigour and exhaustive literature searching can take into account inherent biases within the primary data (i.e. the literature itself).

Finally, Aguilar et al. (2015) claim that “human disturbance of natural habitats has caused disruptions in patterns of mutualistic interactions that may partly explain the presence of the diverse pollinator assemblages that are frequently found in pollination studies”. It seems to us to be disingenuous to argue that pollination syndromes are universally valid and then to essentially concede that there are lots of wrong visitors (“secondary” pollinators), and to explain that with the idea that everything is disturbed in the Anthropocene. If this is really the case then we probably need to throw out a lot of our understanding of evolutionary ecology as a whole, not just studies of plant-pollinator interactions.

Clearly we don’t accept this argument and in fact it has echoes of arguments that have been going on since the 19th century (Waser et al. 2011): more than 130 years ago the Darwinian biologist Hermann Muller was criticising Federico Delpino (one of the original architects of the idea of pollination syndromes) for ignoring the “wrong” flower visitors. Interestingly, Delpino was a fundamentally a teleologist who saw purpose in nature, expressed through (as he perceived them) the highly ordered relationships between flowers and pollinators.

As we discuss in the Waser et al. (2011) paper, Stefan Vogel was another prominent pollination biologist, and advocate of the importance of pollination syndromes, who was also fundamentally teleological in his thinking. I was sad to learn that Stefan passed away very recently, in what I believe is his 90th year. I was fortunate enough to meet Stefan at a symposium in honour of his 80th birthday at the International Botanical Congress in Vienna in 2005. He graciously signed my copy of The Role of Scent Glands in Pollination and said, with a twinkle in his eye, “you and I have probably got a lot to discuss”. Unfortunately we never got the opportunity, but later I dedicated our 2009 paper on Ceropegia pollination to him “in honour of his pioneering work on pollination” in the genus. Stefan’s legacy of research, particularly in the tropical regions of South America, is a fitting tribute to his memory.

Pollination syndromes clearly continue to attract much interest in the scientific literature, and just this week I was intrigued to see a paper by John Benning showing that a species of Ericaceae that looks as though it “should” be pollinated by bees is actually moth pollinated. No doubt the discussion of the evolutionary extent and predictability of pollination syndromes will continue for some time to come.

A new bee for Northamptonshire!

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Back in the summer I produced a series of posts for Pollinator Awareness Week highlighting the pollinators to be found in our own urban garden in Northampton. One of those posts was of what I believed to be the Little flower bee (Anthophora bimaculata), a species which at the time I’d never previously seen. I noted that this was a new urban record for Northampton as my PhD student Muzafar Sirohi had not recorded it during his bee surveys, which I discussed earlier this year.

Some time later I checked the bee records on the National Biodiversity Network (NBN) Gateway site and realised that not only was this the first urban record of the species in Northampton, it was actually the first record for the county of Northamptonshire as a whole! The record has recently been accepted on iRecord and will be added to the NBN records.

Of course this is personally exciting (a new record for a large county found in our back garden) and it adds a significant regional record to the currently known distribution of the species. The map on the BWARS account of Anthophora bimaculata shows that the species is predominantly southern in its distribution, with a few eastern and western outliers. This new record places the species firmly in the centre of England, confirming that it is more widespread than previously assumed.

There are two possible explanations for the discovery of this bee in Northamptonshire. One is that it’s a very recent range expansion and the species is becoming more common and widespread, perhaps as a result of climate change. The second is that it’s always been present in Northamptonshire, but just never recorded. At the moment it’s impossible to decide between these two possibilities as there’s evidence to support both. Not only did Muzafar not record A. bimaculata in his surveys in 2012, neither did Dr Hilary Erenler, Dr Sam Tarrant or Kathryn Harrold in their pollinator surveys in the region between 2007 and 2015. Having said that, we do know that Northamptonshire is a historically under-recorded county for bees as it has no County Recorder for Hymenoptera, and both Hilary and Muzafar recorded species new to Northamptonshire, which I hope to report on at a later stage.

Differentiating between these two scenarios will be difficult and may be impossible unless we can discover previously unknown historical specimens of this bee that were collected in the county, or the species continues to expand in its range.

Understanding the distribution of pollinators such as bees is a key component of initiatives such as the National Pollinator Strategy – if we don’t know where the things we are trying to conserve actually are, how can we conserve them? So it’s very pleasing to be able to make a small contribution to that process from the comfort of our own garden!

Virtual Conference on Pollinators, Pollination and Flowers

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Academic conferences are an important part of what makes science function, via the exchange of ideas and information, publicly and in person. The act of sitting and listening to both established and early career researchers discussing their most recent work, sometimes before it’s in print, is stimulating and exciting, and will never be replaced by digital technology. We’re social animals and conferences, as much as anything else, are social events.

But conferences are becoming more expensive, more frequent, and increasingly out of reach to researchers with limited budgets. They are also getting larger: how many times have you attended a big conference and been torn between which of two (or three or four) talks to go to in parallel sessions? Wouldn’t it be nice to be able to see all of them? Or to go back and hear again the talks that you most enjoyed? Likewise, wouldn’t it be great if your students or members of the public could also see what such conference presentations are like?

With this in mind, some time ago I dreamed up the idea of “virtual conferences” in as an experiment that aims to bring together into one place the most interesting recorded seminars, webinars, conference talks and public lectures that are freely available, and present them as a series of themed mini-conferences. All of the videos in these collections are available on sites such as YouTube* and my role is just to curate them and present them in one place for convenience, as a showcase for some of the best research in biodiversity, evolutionary biology, ecology and conservation, very broadly defined, including inter-disciplinary and policy-related presentations. And just as at a conference, there’s an opportunity to discuss the talks in the comments section on each post and to provide links to other talks on the same topic.

As well as being a service to the research community and the wider public, I hope that these conferences will be a useful teaching resource at advanced undergraduate and postgraduate level.

If anyone is interested in guest-curating a set of presentations in their own subject area on this blog, please do get in touch and I’ll be happy to talk about it.

So here’s the first virtual conference, on (naturally) pollinators, pollination and flowers:

Judith Bronstein (University of Arizona)

The conservation biology of mutualism

Peter Crane (University of Chicago)

The origins of flowers

Jeffery Pettis (USDA Bee Research Laboratory, Maryland)

The role of pesticides in declining pollinator health

Linda Newstrom (Landcare Research, New Zealand)

Pollinator systems in New Zealand and sustainable farming fund

Mace Vaughan and Eric Mader (Xerces Society/USDA/University of Minnesota)

Pollinator habitat assessment and establishment on organic farms

Carlos Vergara, Rémy Vandame, and Peter Kevan (Universidad de las Americas-Puebla/El Colegio de la Frontera Sur/CANPOLIN)

Coffee pollination in the Americas

Claire Kremen (University of California, Berkeley)

Restoring pollinator communities in California’s agricultural landscapes

*I’m assuming that, as all of these videos are in the public domain, none of the presenters or copyright owners objects to them being presented here. If you do, please get in touch and I’ll remove it.

SCAPE day 3 – science on a Sunday

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Last night I added a new edible plant family to my life list – Cornaceae – courtesy of the ever-hospitable Marcin Zych and his home-made fruit liqueurs. The one he opened after dinner was made from the fruit of edible dogwood (Cornus mas) and had been maturing for five years. It was sour but delicious, and very, very strong. That’s my first new addition to the list since my Brazil trip back in in November 2013. One day I will post an annotated list of the biodiversity of plant families I’ve consumed….but not tonight, it’s the end of a tiring final day of the SCAPE conference.

To end the meeting this morning there was a short session of three talks from Klaus Lunau’s sensory ecology group. Klaus started the proceedings with a talk about the role of UV-absorbent dark central “bull’s eyes” in the middle of flowers and compound inflorescences. He concluded that, despite their near mythological status, UV patterns were perhaps no more important than patterns absorbing at other wavelengths and presented some interesting experimental data to support the argument. Over breakfast Klaus and I had discussed the absence of difficult questions at the conference; he felt people were being a little too polite. So I asked him a hard one – whether his findings held up for male bees which don’t collect pollen. He confessed that he’d not tested them and agreed that it would be worth doing: hope he does, will be an interesting test.

Klaus was followed by Saskia Wilmsen who showed us the results of some elegant experiments using artificial “flowers” with different shaped epidermal cells (flat, conical, etc.) These different surfaces have distinctive optical properties in different light conditions, and bees behave in slightly different ways, accordingly. A very cool reminder that as we move to ever finer scales in pollination ecology, from macro biogeographical and community questions, to micro surveys, the layers of complexity just go on increasing.

This latter point was reinforced by the final presentation of the meeting, which was Sebastien Kothe discussing the functional role of the spines possessed by pollen in some plant families, especially Malvaceae. He presented compelling evidence that these spines have evolved in order to reduce their attractiveness to pollen collecting bees. The spines render the pollen hydrophobic meaning that the bees have to use much more nectar to bind it into the pollen baskets. It would be interesting to track the evolution of this echinaceous pollen through the fossil record and to assess whether its appearance coincides with the evolution of particular bee groups.

And with that, the 29th SCAPE meeting was finished except for the usual hugs and goodbyes and promises to meet up again in 12 months time, probably inside the Arctic Circle: it looks as though the 30th meeting will be held at the field station at Abisko.

The rest of Sunday was spent visiting the botanic garden and the art museum in Aarhus, both to be recommended if you have a chance to visit. It’s now 8.15pm and I’m sat at Billund Airport with a large glass of Carlsberg, my first of the trip. It’s been a great meeting and I look forward to repeating it next year, and interacting with such a passionate group of scientists. Over and out from SCAPE.

SCAPE conference 2015 – day 2 – probably the best pollination ecology meeting in the world

SCAPE conference 2015 – day 1 – welcome to the sanatorium

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The first day of the 29^th SCAPE conference drew to a close and as I started to draft this post I could hear around me some intense discussions of Amy Parachnowitsch’s “crazy idea” (her words!) that flowers may be able to “eavesdrop” on one another via their floral scents. It was a very thought provoking way to end a stimulating day. And I look forward to reading the discussion paper on which the talk was based, in Trends in Plant Sciences.

What else did I learn on the first day? Here’s a few things I noted, with a link to the programme, but certainly not an exhaustive list:

Paul CaraDonna told us about the way that interactions between plants and pollinators have a faster turnover early in the season than later in the season. We discussed this afterwards and it could be because of newly emerged, naïve individual pollinators encountering and exploring flowers they’ve not previously seen.

Jane Stout described the history and future of the All-Ireland Pollinator Plan, and how it was driven from bottom-up by two scientists (Jane herself and Una Fitzpatrick) – a salutary tale of what can happen when passionate scientists become advocates for change.

Markus Sydenham discussed his work on power line corridors in Norway and the fact that these linear landscape elements, though artificial, can be good for solitary bees in appropriately managed by cutting and removal of woody vegetation.

A project encouraging organic Danish farmers to assess the quality of their own land for pollinating bees was described by Vibeke Langer. Interesting example of “citizen science” that goes directly to those who might benefit most from larger and more stable pollinator populations.

In Hawaii, Robert Junker and colleagues have found evidence that the flowers of the endemic plant Metrosideros polymorpha have evolved in less than 150 years to be more effectively pollinated by introduced honey bees rather than its native bird pollinators, which have declined substantially. Some individuals of this species seem to be pre-adapted for bee pollination; is this evidence that a larger bee species once existed on Hawaii but is now extinct?

The “complex, messy” ecology behind the co-existence of different Medicago species (facilitated by the interaction of plant genotypic kinship and allelopathic chemicals produced by Thymus species, was the focus of Bodil Ehlers work.

Judith Trunschke showed how ecotype morphology in hawkmoth-pollinated orchid Platanthera bifolia seems to be driven by different pollinators in grassland and woodland habitats. Are we seeing the early stages of the evolution of two new species here?

I had the honour of being the first speaker yesterday morning, talking about the macroecology of wind versus animal pollination, and the University of Northampton was further represented by Kat Harrold, who is working on her PhD as part of the Nene Valley Nature Improvement Area project. Kat presented a short over view of her work during the poster session.

There was much more, of course, and all of it stimulating and interesting, but that’s at least a taster. The conference is taking place in a fascinating conference facility that was a former TB sanatorium. It’s a step up from the ex-leper colony that SCAPE used in Finland a few years ago….

Gull use of urban parks in winter – data I’ll never publish (2)

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For the second in my occasional series of “data I’ll never publish” I want to present a short post about how two species of gulls use an urban Northampton park in the winter. The park is called the Racecourse (I’ve mentioned it before) and is en route to the campus on which I work. It’s long been apparent that the numbers of gulls using the park increases from autumn into winter and declines to zero in the spring and summer, when they head off to breed in and around Northamptonshire’s reservoirs and gravel pits, and further afield. During the winter they spend their time feeding on earthworms, squabbling, chasing crows, and generally relaxing prior to the next breeding season.

What I was interested in knowing was just how quickly the numbers built up, whether it was a slow, steady build-up or a rapid influx of birds, and also the relative numbers of the two commonest species to be found there, Black-headed gull (Chroicocephalus ridibundus) and Common gull (Larus canus).

So during my walks to work between late August 2014 and early January 2015 I simply counted the numbers of birds I saw in the quadrant of the park that I passed. Certainly not the most onerous data collection I’ve ever carried out, and done purely because it interested me, not with any view to conducting a serious study. Here’s the data plotted up as peak birds seen per day, with day of the year on the x-axis, running from 27th August to 5th January:

A few things intrigue me about this. First of all, Common gulls are much more, er, “common”, on the park than Black-headed gulls, despite the fact that Black-headed gulls are far more abundant in the UK during the winter (estimated as 2.2 million versus 710,000 birds). However anecdotally I’ve observed that other parks in Northampton appear to have more Black-headed gulls, suggesting that the two species are to some extent dividing up the urban parks and other grasslands between themselves, like rival gangs with different local patches.

That’s purely speculative and would be worth pursuing as a student project, to test if (a) this hypothesis is correct; and (b) whether that division of the parks is stable between years.

The other thing that’s of interest from these data is that, as you can see from the 10-day moving average, the Common gulls suddenly increase in numbers around the middle of November. I wonder whether this is due to an influx of migrant birds coming in from further north and east in Europe and Scandinavia? At the same time I recorded an unusually large flock of Black-headed gulls: were these also migrants just passing through?

Urban gulls have been getting some bad press recently; but they really are fascinating birds that add a lot to the biodiversity interest of our parks and playing fields. They deserve further study because we take them for granted and there’s really not much published on their urban ecology.

How do artificial nectar feeders affect hummingbird abundance and pollination of nearby plants? A new study in the Journal of Ornithology

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Back in November 2013, during my research and teaching trip to Brazil, I discussed an amazing garden that we visited in which the owner had set up around a dozen hummingbird feeders that were attracting hundreds of individual birds from over 20 species. As I mentioned, one of the owner’s concerns was that by feeding the birds he might be negatively affecting the reproduction of hummingbird-pollinated plants in the surrounding forest. I thought it unlikely but there have been very few tests of this idea, and none in that part of South America.

After I left, a Master’s student called Jesper Sonne, based at the Center for Macroecology and Climate in Copenhagen, worked with my Brazilian and Danish colleagues on collecting data to address this question. Between us we analysed and wrote up the results, and have recently published the paper in the Journal of Ornithology under the title “Spatial effects of artificial feeders on hummingbird abundance, floral visitation and pollen deposition“.

The abstract is below and if anyone wants a PDF, please drop me a line. But the take home message is that although these feeders have a significant local effect on hummingbird abundance, there’s no evidence that they affect plant reproduction in the vicinity. It’s nice when predictions prove correct….

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Abstract

Providing hummingbirds with artificial feeders containing sugar solution is common practice throughout the Americas. Although feeders can affect hummingbird foraging behavior and abundance, it is poorly understood how far this effect may extend. Moreover, it remains debated whether nectar-feeders have a negative impact on hummingbird-pollinated plants by reducing flower visitation rates and pollen transfer close to the feeders. Here, we investigated the effects of distance to nectar-feeders on a local hummingbird assemblage and the pollination of Psychotria nuda (Rubiaceae), a hummingbird-pollinated plant endemic to the Brazilian Atlantic Rainforest. At increasing distance (0–1000 m) from a feeding-station, where hummingbirds have been fed continuously for the past 13 years, we quantified hummingbird abundance, and rates of flower visitation and pollen deposition on P. nuda. We found that hummingbird abundance was unrelated to distance from the feeders beyond ca. 75 m, but increased steeply closer to the feeders; the only exception was the small hummingbird Phaethornis ruber, which remained absent from the feeders. Plants of P. nuda within ca.125 m from the feeders received increasingly more visits, coinciding with the higher hummingbird abundance, whereas visitation rate beyond 125 m showed no distance-related trend. Despite this, pollen deposition was not associated with distance from the feeders. Our findings illustrate that artificial nectar-feeders may locally increase hummingbird abundance, and possibly affect species composition and pollination redundancy, without necessarily having a disruptive effect on pollination services and plants’ reproductive fitness. This may apply not only to hummingbirds, but also to other animal pollinators.

BBC Wildlife magazine for October features Northampton harvest mice research