Category Archives: Pollination

Virtual Conference on Pollinators, Pollination and Flowers

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….

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.

How much do we really understand about pollination syndromes?

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Ecologists and evolutionary biologists have, for many years, sought to document repeated patterns that they see in nature; to understand the processes that determine these patterns; and to make predictions about how and when they are going to be observed in the future or in other parts of the world. There are many examples of such patterns, including: cyclical population dynamics of species such as lemmings; the occurrence of specific types of plant communities (e.g. rainforest, grasslands) in areas with particular climates; and convergent evolution of unrelated species to similar ecological niches, such as large, predatory placental and marsupial mammals (e.g. the dog and wolf family compared to the Tasmanian “wolf”).

An example of convergent evolution that has fascinated botanists since the 19^th century is the idea of “pollination syndromes”, which are sets of flower characteristics that have repeatedly evolved in different plant families due to the convergent selection pressures applied by some groups of pollinators. Thus, red, scentless flowers producing lots of nectar are typical of many hummingbird pollinated plants in the New World, whilst white, night-scented flowers often signify moth pollination. Good examples of plant species possessing these archetypical flower traits are have been used as text book examples for decades, repeatedly used to illustrate the predictable and specialised nature of some plant-pollinator interactions.

The problem is that until recently the pollination syndromes have rarely been subjected to critical tests of their frequency and predictive value (Ollerton et al. 2009 and references therein). It’s been tacitly assumed that (after more than 150 years of study) we clearly know all there is to know about them, even though there have been criticisms levelled at the syndromes since their inception, a fact that has been subsequently ignored (Waser et al. 2011).

However in the last 20 years biologists have begun to seek answers to questions such as: How often do plant species conform to the expectations of the classical pollination syndromes? How good is our ability to predict the pollinators of a plant based just on its flower characteristics? What is the role played by flower visitors that do not conform to the predictions of the pollination syndromes? Similarly, what is the role of animals that steal nectar or pollen, or act as herbivores, in shaping flower traits? What new examples of convergent evolution of flower traits remain to be discovered?

Research conducted in many different parts of the world has addressed these questions, questions which some biologists had assumed were already answered or which were not worth asking in the first place. And the answers to them are proving to be both surprising and controversial.

For example, the most comprehensive test of the frequency and predictability of pollination syndromes that has been conducted to date (Ollerton et al. 2009) concluded that only a small proportion of the 352,000 species of flowering plants could be categorised into the pollination syndromes as classically described. Likewise, they estimated that the predictive power of the pollination syndromes was about 30%. Other studies have shown that “secondary” flower visitors can be just as, or more, effective pollinators than the “primary” pollinator predicted by the syndromes (e.g. Waser & Price 1981,1990, 1991); that floral antagonists can play an important a role in shaping flower traits (e.g. Junker and Parachnowitsch 2015 and references therein); and that there are still examples of convergent evolution to “unexpected” pollinators waiting to be discovered in less well researched parts of the world, which in fact is most of the world (Ollerton et al. 2003).

Recently the very prestigious journal Ecology Letters published a paper that has challenged the challengers. Rosas-Guerrero et al (2014), by using a statistical technique called meta-analysis underpinned by a review of the available literature, suggested that pollination syndromes are much more predictable than Ollerton et al. (2009) concluded, and perhaps as high as 75%. However some of my collaborators and I see problems with their approach to studying pollination syndromes that have biased the conclusions that they draw, and therefore undermined the robustness of those conclusions, which we set out in a response to their original paper (Ollerton et al. 2015). We originally tried to publish this in Ecology Letters but for some reason the journal was not interested; it’s therefore freely available from Journal of Pollination Ecology if you follow that link.

I won’t go into the detail of what we perceive as problems in Rosas-Guerrero et al.’s approach to testing the syndromes (you can read the paper for yourself) but in summary they relate to how the literature review was conducted (which failed to include all of the studies that could have provided data for their meta-analysis); the significant bias in the current literature because plant-pollinator interactions are not studied randomly (biologists are often drawn to large-flowered plants possessing those archetypical, classical flower traits associated with particular syndromes); the variation in how different researchers determine the effectiveness of the pollinators in their system, meaning that these studies are not always comparable; and issues around annual variation in pollinator identity and presentation of data.

Despite providing a focus and framework for understanding pollination biology for over 150 years, the pollination syndromes continue to surprise us and to provide a vital antidote to scientific hubris: we really do not understand nearly as much about them as we assume.

In an era when we are more and more concerned about loss of pollinator diversity, including extinction at both a species- and country-level, do these debates really matter or are they of purely academic concern, of interest to a few botanists and ecologists? As you might expect, I’d argue that they do matter: there are still some fundamental aspects of pollination ecology that we don’t completely understand, or have only recently been seriously addressing, some of which I’ve worked on myself and which I’ve highlighted in this blog. These include the number of flowering plants that require animal pollination, the diversity of pollinators at a global and regional level, the relative importance of different types of pollinators, and whether or not plants and pollinators are more specialised in tropical compared to temperate communities. Without some of this fundamental knowledge we are unable to make effective arguments, policies and strategies for conserving pollinators.

References

Junker RR, Parachnowitsch AL (2015) Working towards a holistic view on flower traits—how floral scents mediate plant–animal interactions in concert with other floral characters. Journal of the Indian Institute of Science 95:43–67.

Ollerton J, Johnson SD, Cranmer L, Kellie S (2003) The pollination ecology of an assemblage of grassland asclepiads in South Africa. Annals of Botany 92:807–834.

Ollerton J, Alarcón R, Waser NM, Price MV, Watts S, Cranmer L, Hingston A, Peter CI, Rotenberry J (2009) A global test of the pollination syndrome hypothesis. Annals of Botany 103:1471–1480.

Rosas-Guerrero V, Aguilar R, Marten-Rodriguez S, Ashworth L, Lopezaraiza-Mikel M, Bastida JM, Quesada M (2014) A quantitative review of pollination syndromes: do floral traits predict effective pollinators? Ecology Letters 17: 388–400.

Waser NM, Price MV (1981) Pollinator choice and stabilizing selection for flower color in Delphinium nelsonii. Evolution 35:376–390.

Waser NM, Price MV (1990) Pollination efficiency and effectiveness of bumble bees and hummingbirds visiting
Delphinium nelsonii. Collectanea Botanica (Barcelona) 19:9–20.

Waser NM, Price MV (1991) Outcrossing distance effects in Delphinium nelsonii: pollen loads, pollen tubes, and seed set.
Ecology 72:171–179.

Waser NM, Ollerton J, Erhardt A (2011) Typology in pollination biology: lessons from an historical critique. Journal of Pollination
Ecology 3:1–7.

Garden pollinators for PAW no. 6 – Buff-tailed bumblebee (Bombus terrestris)

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It would be impossible to write a series of blog posts about garden pollinators for Pollinator Awareness Week without considering the bumblebees (genus Bombus) and I intend to devote the last two posts to that group of bees. The bumblebees are arguably the UK’s most important pollinators of both wild and crop plants, certainly later in the season when colony numbers have increased. Earlier in the season it’s the solitary bees such as the Orange-tailed mining bee that are predominant.

Although common and widespread in gardens, the Buff-tailed bumblebee (Bombus terrestris) belongs to a group of bees in which the workers are rather variable in appearance and can be very difficult to distinguish from those in the Bombus lucorum group, which includes two other species (B. cryptarum and B. magnus).

This is a truly social species with an annual nest comprising workers and a queen. Nests are founded by queens that have mated the previous year and hibernated. They usually choose old rodent nests in which to begin their colonies, which is why they are sometimes found in garden compost bins. An interesting question that I’ve not seen answered is whether the queens actively displace mice or voles from such nests: does anyone know? This association between bumblebees and mice led Charles Darwin and Thomas Huxley into some speculation as to the role of spinsters in the British Empire.

In my garden the Buff-tailed bumblebee pollinates a range of crops including strawberries, squashes, courgettes, blackberries, runner beans, french beans, tomatoes, and raspberries. As the photo above shows they also visit the flowers of passion fruit, where they seem to be more effective than the smaller honey bees and solitary bees.

Garden pollinators for PAW no. 5 – Orange-tailed mining bee (Andrena haemorrhoa)

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The Orange-tailed mining bee (Andrena haemorrhoa) is also referred to as the Early mining bee due to its habit of emerging from over-wintered nests as early in the year as March. In truth, however, many Andrena species put in an early appearance, making them important pollinators of orchard fruit such as apples, which you can see from the photograph above, taken in my urban garden earlier this year. So “Orange-tailed” is a more descriptive name.

Thanks to the Orange-tailed mining bee and other early bees, this unnamed apple variety (which Karin and I rescued from the bargain area of a local garden centre) has gone on to produce a heavy crop of eating apples (see below). There’s considerable interest in the role of wild bees such as these as pollinators of fruit in commercial orchards, not just in Europe but in the USA too, where other Andrena spp. also pollinate apples.

The epithet “Mining bees” refers to the fact that these solitary species of the genus Andrena usually make their nests in soil, excavating deep tunnels in which to construct individual cells. It’s another generalist, taking pollen and nectar from a wide variety of garden and wild flowers. Dandelions are particularly important early in the year – so don’t over-manage your lawn and allow some to flower!

Garden pollinators for PAW no. 4 – Gatekeeper butterfly (Pyronia tithonus)

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For my fourth contribution to Pollinator Awareness Week I’m going to highlight the Gatekeeper (Pyronia tithonus), a butterfly that I featured on this blog last year. As I noted in that post, it’s fairly rare to have Gatekeepers in an urban garden which indicates that the shrubs and hedges grown by myself and my neighbours are providing the right microclimate for the adults. In addition the overgrown lawns of some adjacent gardens give opportunities for egg laying as the caterpillars are grass feeders.

Adult butterflies are very well camouflaged when resting with their wings folded. They take nectar from a range of plants in my garden but particularly love the dark, heavily scented infloresences of the buddleia variety pictured here. They also visit the wild blackberries scrambling through the hedge that separates us from next door’s garden and probably pollinate those flowers. Although it’s often said that butterflies are poor pollinators compared to bees, due to their general un-hairiness and habit of holding themselves above the stamens and stigmas in a flower, it very much depends on the type of flower. We have an unpublished manuscript that I hope to submit to a journal later this year showing that butterflies are actually better pollinators of one grassland plant than bumblebees.

Garden pollinators for PAW no. 2 – Marmalade hoverfly (Episyrphus balteatus)

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One of the most frequently encountered of hoverfly species in urban gardens is the beautifully named Marmalade hoverfly (Episyrphus balteatus). This insect is a “true fly” of the order Diptera that is sometimes confused with superficially similar wasps (order Hymenoptera), though (as the common name suggests) the species is translucent orange and black in colour rather than waspish yellow and black. It also has a very flat abdomen whereas wasps are rounded, and they certainly don’t sting.

Individual insects are relatively ineffective as pollinators – they are small and not very hairy, so carry little pollen compared to bumblebees for instance. However they can be extremely abundant and that abundance makes up for any individual ineffectiveness. It’s a real generalist, visiting lots of different types of flowers, and in my garden they visit radishes (as I noted last year) and raspberries.

I often see individuals patrolling crops such as runner beans, not visiting the flowers but laying eggs on leaves and stems: the larvae of the Marmalade hoverfly is carnivorous and feeds on aphids, so it plays an interesting dual role of both pollinator and pest controller. Definitely a gardener’s friend!