Category Archives: Brazil

Generalist pollination can evolve from more specialised interactions: a new study just published

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There’s a long-standing idea in biology that ecological specialisation is an evolutionary “dead end” from which species can never emerge.  In other words, if a species becomes so adapted to a particular ecological strategy (could be feeding or habitat requirements or how it interacts with other species ) then no amount of natural selection will result in its descendants evolving different strategies, thereby diversifying into new species.  In particular it’s traditionally thought that evolving broader, “generalist” strategies from narrower, “specialised” ones is highly unlikely.

This has been much discussed in the literature on the ecology and evolution of pollination systems, where traditionally this “dead end” scenario has been accepted.  However a small number of case studies have shown that generalised pollination systems can evolve within much more specialised clades, beginning with Scott Armbruster and Bruce Baldwin’s study of Madagascan Dalechampia (Euphorbiaceae), published in Nature in 1998.

To this limited body of examples we can now add another case study: in the genus Miconia (Melastomataceae), generalist nectar/pollen rewarding strategies can evolve within a clade of plants that predominantly uses a more specialised, buzz-pollinated strategy involving just bees.

The work is part of the PhD research of Vinicius de Brito who is one of the researchers I was privileged to do some field work with in Brazil when I was there in 2013 – see my post: “It’s called rainforest for a reason, right?  Brazil Diary 6“.  Vini is the guy on the left of the photo accompanying this post.  Here’s the citation and a link:

de Brito, V.L.G., Rech, A.R., Ollerton, J., Sazima, M. (2017) Nectar production, reproductive success and the evolution of generalised pollination within a specialised pollen-rewarding plant family: a case study using Miconia theizans. Plant Systematics and Evolution doi:10.1007/s00606-017-1405-z 

Here’s the abstract:

Generalist plant–pollinator interactions are prevalent in nature. Here, we untangle the role of nectar production in the visitation and pollen release/deposition in Miconia theizans, a nectar-rewarding plant within the specialised pollen-rewarding plant family Melastomataceae. We described the visitation rate, nectar dynamics and pollen release from the poricidal anthers and deposition onto stigmas during flower anthesis. Afterwards, we used a linear mixed model selection approach to understand the relationship between pollen and nectar availability and insect visitation rate and the relationship between visitation rate and reproductive success. Miconia theizans was visited by 86 insect species, including buzzing and non-buzzing bees, wasps, flies, hoverflies, ants, beetles, hemipterans, cockroaches and butterflies. The nectar produced explained the visitation rate, and the pollen release from the anthers was best explained by the visitation rate of pollinivorous species. However, the visitation rates could not predict pollen deposition onto stigmas. Nectar production may explain the high insect diversity and led to an increase in reproductive success, even with unpredictable pollen deposition, indicating the adaptive value of a generalised pollination system.

As always, I’m happy to send a PDF to anyone who wants a copy, just drop me an email.

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Filed under Bees, Biodiversity, Brazil, Butterflies, Evolution, Hoverflies, Mutualism, Pollination, Wasps

The road to degradation: is “naming all the species” achievable or even desirable?

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In 2013 Mark Costello, Robert May and Nigel Stork published a review paper in the journal Science called “Can We Name Earth’s Species Before They Go Extinct?”  It’s a paper that I discuss with my students in their final year Biodiversity and Conservation module, and it always generates a lot of interest, and it’s has been well cited since it first appeared (143 citations* to date according to Web of Science).  There was an interesting response by Mora et al., with a riposte by Costello et al., but overall the original paper has been rather influential in framing some discussions about taxonomic effort and description of species, and the idea that we can “name everything” with additional resources.  At the end of the review Costello and colleagues answered their own question by stating: “We believe that with modestly increased effort in taxonomy and conservation, most species could be discovered and protected from extinction” [my emphasis].

Is their optimism justified?  Can “most species be discovered”?  And what are the implications for how we go about “discovering” these species that are unknown to science?

In my professional life I’ve been fortunate enough to carry out field work with some great colleagues in some wonderful parts of the world, including tropical rainforest and savannah in Guyana and Gabon, mountain scrub in the High Andes of Peru, seasonal dry forest in Australia, montane grasslands in South Africa, Namibian desert, and Brazilian cerrado and Atlantic rainforest.  All of these were sites where non-biologists would rarely venture: off the beaten track and (usually**) away from the typical tourist haunts.  It would be tempting to describe these places as “remote” but really they were not, because they all shared something in common: accessibility.  We were able to reach these sites by traveling along roads, of variable quality, usually in four-wheel drive vehicles.  The roads were often not in good condition, and frequently not metaled, but they were roads nonetheless.

It’s sometimes said that if one were to map the geographical coordinates of plant specimens stored in herbariums such as the one at Kew, you would end up with a road map of the world.  That’s because collecting biological specimens, or carrying out field work, requires us to be able to gain access to an area.  And accessibility usually means roads, unless one is working on the coast or along a river or lake, or have lots and lots of funding to allow teams to be helicoptered into an area (which is rare, but makes for exciting television).  Therefore most collecting of biological specimens is done in areas not far from roads.

So, any initiative that intends to “name all the species” in a particular group is going to require access to the remotest parts of the planet, areas that currently have no roads running through them.

There are still areas of the world that we can consider “remote” and “wilderness”, areas that are more than 100km from the nearest road – as a study published at the end of 2016 demonstrated.  But these are often found in the most biologically rich parts of the planet, for example tropical rainforest and mountainous areas, where we wouldn’t necessarily want to put roads to make them accessible to taxonomists (or even ecologists).  That’s because where roads go, people go, and accessibility to an area is usually followed by exploitation and degradation: illegal hunting, logging, mining, poaching of specimens for sale, etc. etc.

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Now, don’t get me wrong, taxonomy is absolutely vital to the conservation of the earth’s biodiversity.  It also underpins much ecological, bio-molecular and agricultural research and technology.  But the trade off for taxonomists is that they must gather their specimens and data from accessible areas, and that often means roads, and roads mean degradation.

The impetus for this post came from Twitter where a taxonomist highlighted the very good work done by the Virtual Institute of Spider Taxonomy Research (VINT) and described it as an “initiative to discover all spider species of the world in 30 years”.  Interestingly I can’t find that aspiration on the VINT website, but if it exists I’m not sure it’s achievable for spiders or any other diverse group of species, without being able to access parts of the world that are best left un-degraded.  Again, this is particularly true of the tropics where species can have very limited distributions.  A number of years ago an Australian botanist told me about how he was only able to collect some epiphytic Hoya specimens in Papua New Guinea by going into areas of rainforest that had been illegally logged, removing the plants from crowns of the felled trees, with no little risk to his own safety if the loggers had spotted him.  Some of those species might have remained undescribed if the area had not been opened up by a road prior to deforestation.  That would have been a loss for Hoya taxonomy, but surely positive for conservation.

Can “most species be discovered”?  Is this even a desirable thing?  I used to think so, because of the oft-stated view that we can’t conserve what we don’t know.  Now I’m not so sure, for reasons I hope I’ve articulated.  But as always I’d welcome your comments and criticisms.

 

*Including one in the conference: Annual Forum on Grumpy Scientists: the Ecological Conscience of a Nation:Royal Zoological Society, Sydney, Australia.  I’d have liked to have been a fly on the wall at that meeting!

**Usually, but not always: I have a few papers where some or all data collection was done in and around back-packers hostels, hotels, and tourist lodges.  Hey, you take your opportunities where you find them in this game!

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Filed under Biodiversity, Brazil, Spiders, University of Northampton

The macroecology of animal versus wind pollination – a new study just published

In collaboration with colleagues in Brazil, Denmark, and elsewhere in the UK, we’ve just published a new research paper which looks at the global spatial distribution of wind and animal pollinated plant species, and the underlying historical and contemporary ecological causes of that distribution.  It’s a study that builds on my “How many flowering plants are animal pollinated?” paper in Oikos, and has been a long time in its gestation.  We’re very excited by its findings and plan to develop this project in the future.

As a bonus we made the cover of the journal with the amazing image below!  Big thanks to Pedro Viana and Jesper Sonne for the photos.

Here’s the citation with a link to the publisher’s website; the abstract is below.  If anyone wants a PDF copy, please ask.

Rech AR, Dalsgaard B, Sandel B, Sonne J, Svenning J-C, Holmes N & Ollerton J (2016) The macroecology of animal versus wind pollination: ecological factors are more important than historical climate stability. Plant Ecology & Diversity 9: 253-262

 

Abstract:

Background: The relative frequency of wind- and animal-pollinated plants are non-randomly distributed across the globe and numerous hypotheses have been raised for the greater occurrence of wind pollination in some habitats and towards higher latitudes. To date, however, there has been no comprehensive global investigation of these hypotheses.

Aims: Investigating a range of hypotheses for the role of biotic and abiotic factors as determinants of the global variation in animal vs. wind pollination.

Methods: We analysed 67 plant communities ranging from 70º north to 34º south. For these we determined habitat type, species richness, insularity, topographic heterogeneity, current climate and late-Quaternary climate change. The predictive effects of these factors on the proportion of wind- and animal-pollinated plants were tested using correlations, ordinary least squares (OLS) and logistic regression analyses with information-theoretic model selection.

Results: The proportion of animal-pollinated plant species was positively associated with plant species richness and current temperature. Furthermore, in forest, animal pollination was positively related to precipitation. Historical climate was only weakly and idiosyncratically correlated with animal pollination.

Conclusion: Results were consistent with the hypothesised reduced chance for wind-transported pollen reaching conspecific flowers in species-rich communities, fewer constraints on nectar production in warm and wet habitats, and reduced relative effectiveness of wind dispersal in humid areas. There was little evidence of a legacy of historical climate change affecting these patterns.

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Filed under Biodiversity, Biogeography, Brazil, Climate change, Macroecology, Pollination

The integration of alien plants in mutualistic plant–hummingbird networks – a new study by Maruyama et al. (2016)

The collaborations with researchers in Brazil and Denmark in which I’ve been involved in recent years, focused particularly on hummingbirds and networks of plant pollinator interactions, have been very productive, most recently seen in a study of the effects of hummingbird feeders on diversity and abundance of the birds.

This collaboration continues with a new study that has just been published in the journal Diversity and Distributions which deals with the way in which non-native plant species are exploited by assemblages of hummingbirds in the New World.  Here’s the abstract:

 

Aim:  To investigate the role of alien plants in mutualistic plant–hummingbird networks, assessing the importance of species traits, floral abundance and insularity on alien plant integration.

Location: Mainland and insular Americas.

Methods: We used species-level network indices to assess the role of alien plants in 21 quantitative plant–hummingbird networks where alien plants occur. We then evaluated whether plant traits, including previous adaptations to bird pollination, and insularity predict these network roles. Additionally, for a subset of networks for which floral abundance data were available, we tested whether this relates to network roles. Finally, we tested the association between hummingbird traits and the probability of interaction with alien plants across the networks.

Results: Within the 21 networks, we identified 32 alien plant species and 352 native plant species. On average, alien plant species attracted more hummingbird species (i.e. aliens had a higher degree) and had a higher proportion of interactions across their hummingbird visitors than native plants (i.e. aliens had a higher species strength). At the same time, an average alien plant was visited more exclusively by certain hummingbird species (i.e. had a higher level of complementary specialization). Large alien plants and those occurring on islands had more evenly distributed interactions, thereby acting as connectors. Other evaluated plant traits and floral abundance were unimportant predictors of network roles. Short-billed hummingbirds had higher probability of including alien plants in their interactions than long-billed species.

Main conclusions: Once incorporated into plant-hummingbird networks, alien plants appear strongly integrated and, thus, may have a large influence on network dynamics. Plant traits and floral abundance were generally poor predictors of how well alien species are integrated. Short-billed hummingbirds, often characterized as functionally generalized pollinators, facilitate the integration of alien plants. Our results show that plant–hummingbird networks are open for invasion.

 

The full reference is: Maruyama, P.K. et al. (2016) The integration of alien plants in mutualistic plant–hummingbird networks across the Americas: the importance of species traits and insularity.  Diversity and Distributions (in press).

Happy to send a PDF to anyone who would like one.

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Filed under Biodiversity, Biogeography, Birds, Brazil, Pollination

Pollinators and pollination – something for the weekend #9

The latest in an (ir)regular series of posts to biodiversity-related* items that have caught my attention during the past few weeks; this one’s focused on pollinators and pollination because there’s been so much emerging on this recently it’s been impossible to decide what to write more fully about!

 

Feel free to recommend links that have caught your eye.

*Disclaimer: may sometimes contain non-biodiversity-related items.

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Filed under Bees, Biodiversity, Birds, Brazil, Ecosystem services, Evolution, Honey bees, Macroecology, Pollination

SCAPE day 3 – science on a Sunday

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.

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Filed under Bees, Biodiversity, Brazil, Pollination

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

Hummingbirds on feeds in Brazil

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.

Hummingbirds on feeds in Brazil 2

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Filed under Biodiversity, Birds, Brazil, Gardens, Pollination