Category Archives: British Ecological Society

The explosion in orchids as houseplants: what does it tell us about how flowers evolve?

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One of the major trends in horticulture over the last 20 years or so has been the rise in popularity of orchids as house plants. Orchids used to have a reputation as being delicate, choosy, costly things that needed expensive glasshouses, heating, and humidity systems to grow. Some groups of orchids are certainly like that, but many are not (Orchidaceae is one of the two largest families of plants, after all). These days it’s impossible to walk into any supermarket or department store and not see orchids for sale at a reasonable price, orchids that are tough and can withstand the relatively dry, centrally heated houses in which most of us in Britain live.

The majority of these orchids are varieties of Phalaenopsis, the moth orchids. Intensive hybridisation by commercial growers has meant that there is an almost inexhaustible range of flower colours, shapes, sizes and patterning available. Take a look at this gallery of images and you’ll see what I mean, or go into a shop that sells such orchids and observe that almost no two are alike.

This is the stuff of natural selection: genetic variation in the phenotype that can be acted upon by a selective agent. In this case it’s the growers of orchids who choose the most attractive types to sell and discard the others. If this variation emerged in wild populations most of it would disappear over time, but some, just occasionally, would be selected for by a different group of pollinators and go on to form a new species. This is much more likely to happen if the individuals with this variation are isolated from the rest of the population in time or space, for example if they flower later or have been dispersed to a distant valley or mountaintop (termed allopatric speciation). But it can also happen within populations – sympatric speciation.

Back in 1996, near the start of this orchid explosion, one of my earliest papers was a speculative commentary in Journal of Ecology called “Reconciling ecological processes with phylogenetic patterns: the apparent paradox of plant-pollinator systems”. It generated some interest in the field at the time and has picked up >250 citations over the years, mostly other researchers using it as supporting evidence for the discrepancies we see when trying to understand how flowers evolve within a milieu of lots of different types of potential pollinators selecting for possibly diverse and contradictory aspects of floral form. In that paper I made a passing comment that I expected the reviewers to criticise, which they did not. Once it was published I thought that perhaps other researchers in the field would critique it or use it as a jumping off point for further study, which has not really happened either. This is what I wrote:

“It appears that pollination systems are labile and may evolve quite rapidly….plant breeders can obtain a fantastic range of horticultural novelties through selective breeding over just a few generations.”

This is horticulture holding up a mirror to the natural world and saying: “This is how we do it in the glasshouse, look at the variety we can produce over a short space of time by selecting for flower forms; can nature do it as quickly, and if so what are the mechanisms?”

I still believe that pollination ecologists could learn a lot from horticulture and there’s some fruitful (flowerful?) lines of enquiry that could be pursued by creative PhD students or postdocs. Here’s one suggestion: part of the reason why these Phalaenopsis orchids are so popular as house plants is that they have very long individual flower life times, often many weeks. Now we suspect that floral longevity is under strong selection; see for example research by Tia-Lynn Ashman and Daniel Schoen in the 1990s. This showed that there is a negative correlation between rate of pollinator visitation and how long flowers stay open. Plants with flowers that are not visited very frequently stay open much longer, for example the bird-pollinated flowers of the Canary Islands that may only be visited once or twice a day, and which can remain open for more than 20 days. Is the floral longevity shown by these orchids (or other groups of plants that have been horticulturally selected) beyond the range found in natural populations? If so, what are the underlying physiological mechanisms that allow such extreme longevity? If not, does this mean that there is an upper limit to the lifespan of flowers, and if so, why?

In the mean time I’m going to enjoy the orchids above that sit on our kitchen windowsill. They actually belong to my wife Karin who has developed something of an interest in them in recent months. The big spotty one is a late birthday gift for her that I picked up this morning from a local flower shop, and which stimulated this post as I was walking home. I’d bet that we never see another one like it!

Silver Medal for the BES’s pollinator’s display at RHS Chelsea Flower Show!

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RHS Silver Medal

An early train to London yesterday got me to the RHS Chelsea Flower Show in time for the gates opening at 8am. I’d agreed to spend the day staffing the British Ecological Society’s Animal Attraction: The garden and beyond display, which deals with the relationships between plants and their pollinators – see my recent posts here and here.

The first thing I noticed as I approached the display was how impressive and well designed it looked, with some wonderful planting to complement the simple, bold scientific information. The second thing I noticed was that we had won a Silver Medal! The whole team was very pleased – it’s the third year that the BES has been represented at Chelsea, but the first time that it’s won a medal. I’m proud to have made a small contribution to that by advising on the plants and the scientific content, but the main kudos goes to the BES’s staff and to the garden designer Emily Darby.

Over the course of a long day we talked to hundreds of visitors about the display, what it represented, and the different ways that flowers are adapted to their pollinators. There was a huge amount of public interest and support, very gratifying to see. Here’s some pictures from the day:

RHS display

RHS crowd

RHS crowd with fig

RHS Jeff

RHS display

Pollinators, yeast, and the BES at RHS Chelsea – official press release

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The official press release for this week’s British Ecological Society display at the RHS Chelsea Flower Show, which I talked about last week, was embargoed until this morning; here’s the full text that’s been tailored by the University of Northampton press office:

Scent, colour and form all shape the choices we make about what to plant in our gardens. Gardeners know that flowers produce nectar and scent to attract the birds, bats, insects and other animals they rely on as pollinators, but few realise that organisms too small to see with the naked eye also play a vital role in this process.

Ecologists have discovered that a yeast called Metschnikowia plays a key part in the pollination story and next week, for the first time, visitors to the RHS Chelsea Flower Show will be able to get a sniff of it and see how it looks under the scanning electron microscope.

The yeast forms part of the British Ecological Society‘s Animal Attraction: The garden and beyond display, which focuses on the relationships between plants and their pollinators – relationships that are amazing in their diversity as well as crucial to global food security. The University of Northampton’s Professor of Biodiversity, Jeff Ollerton, has been advising the British Ecological Society on the project.

Metschnikowia is ubiquitous, present in most flowers in most gardens, yet ecologists are only just beginning to uncover its mysterious role in pollination. The yeast is studied in only four laboratories in the world and Dr Manpreet Dhami from Stanford University has donated the yeast for the British Ecological Society’s garden.

Like other yeasts, Metschnikowia may produce volatile chemicals that mimic the scent flowers use to attract pollinators, thus helping the flower to attract more pollinators and therefore set more seed. In return, the yeast becomes attached to birds, insects and other pollinators, which it relies on for dispersal.

Professor Ollerton explained: “It was a pleasure to work with the British Ecological Society on this project as it highlights two important points about the natural world: that pollinators other than bees are just as important to both wild plants and crops, and that the diversity and abundance of many of these groups is declining worldwide.” Professor Ollerton’s recent study, published in Science, found that 23 species of British bees and flower-visiting wasps have gone extinct since the 19th century.

According to Jessica Bays of the British Ecological Society: “To tackle this decline, we need to understand its causes, including climate change, habitat loss and pesticide use, and we also need to understand the role played by yeasts such as Metschnikowia, which is why we decided to bring it to Chelsea this year.”

Tickets are still available for the RHS Chelsea Flower Show 2016 – for more information click here.

Pollinators at RHS Chelsea Flower Show

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Pollinators, as regular readers of this blog will know, are diverse and important, both ecologically and agriculturally. But that diversity is declining and it’s an issue that deserves greater publicity and action.

To that end, for the past eight months I’ve been advising a team from the British Ecological Society (BES) on the content for a display at the RHS Chelsea Flower Show which is running all next week. The display is called “Animal Attraction: The Garden and Beyond” – if you follow that link you’ll get a sense of what the display is all about, but in essence there are three key messages that the BES is trying to get across:

Celebrating the diversity of pollinators (not just bees!) both in the UK and globally.
Flowers have evolved many different ways of attracting and rewarding pollinators, leading to the fantastic diversity of floral form that gardeners appreciate.
Planting a diversity of flowers in your garden can only be a good thing for helping conserve pollinator populations.

As you can see from my wristband, I’ll be helping to staff the stand all day Tuesday 24th May, so if you’re at the show come and say hello and take a look at what the BES team has produced.

7 minutes is a long time in science, 7 goals is a big win in football (BES Macroecology meeting day 2)

Scientists Must Write (and Speak and Listen and Review and Edit)

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“Scientists Must Write” was the title of a book published back in the late 1970s by a former tutor of mine, Robert Barrass, at what was then Sunderland Polytechnic (now the University of Sunderland). I had assumed the book was now a long gone publishing memory and no longer available. But it turns out that Robert updated it in the early 2000s and it’s still in print. Almost 30 years (30!) later I can clearly remember Robert impressing upon us the importance of good writing skills for scientists-in-training. At the time I was as far from being a professional scientist as it’s possible to be and so didn’t fully grasp this, but nonetheless what he said chimed with my own notions that writing was important, even for a scientist.

Nowadays I realise that it’s not just the writing of standard, academic papers, book chapters and books which is essential: writing of all kinds is a necessary facet of the life of a research active scientist. This June sees the publication of two contrasting articles that illustrate this point. The Royal Horticultural Society’s journal The Plantsman has published a piece entitled “The Importance of Native Pollinators“, whilst the historical journal Notes and Records of the Royal Society has published my paper on “John Tweedie and Charles Darwin in Buenos Aires“. Neither of these is standard academic fare, at least for me. The first is a popular article aimed largely at gardeners and others interested in understanding more about pollinator conservation. The second, whilst academic and rigourously peer reviewed, is primarily historical rather than scientific.

Why am I writing popular conservation articles and historical papers? Largely for different reasons, though they are linked by my overall fascination with biodiversity. The Plantsman article is an example of taking ideas and findings from the LBRG‘s research and presenting it to a wider audience who might, at the least, find it interesting and hopefully useful. One might describe it as “popular science” though I don’t really like the term: it suggests that it’s somehow different to “real” science, which is not the case: it’s really only the format of the presentation which is different.

The John Tweedie/Charles Darwin paper reflects my desire to understand where our scientific knowledge of biodiversity comes from. As scientists and conservationists, we draw conclusions about species’ distributions, conservation threats, extinctions, and so forth, based on information from specimens that have been collected by people like Tweedie and Darwin, and curated at places such as Kew and the Natural History Museum. By its nature it’s a historical process and historical research helps us to understand how we arrived at our current understanding. The only reason we know that 23 species of bee have gone extinct in England since about 1800 for example, as I cite in my Plantsman article, is that over the past two centuries specimens and observations have been recorded and analysed. This is an ongoing process, exemplified by the BWARS project mapping the spread of Bombus hypnorum the most recent addition to the UK’s native bee list.

As well as writing we scientists gain much from listening to what others in our field have to say and a well attended, and very interesting, meeting in London last week launched the British Ecological Society’s Macroecology Special Interest Group . The range of talks spanned community structure, interaction networks, ecosystem services, latitudinal gradients and disease biology, all at the large spatial and temporal macroecological scales covered by this subdiscipline of ecology. Or is it really a multidisciplinary field, a merging of old fashioned biogeography with more modern ecological approaches? Who knows, perhaps this is sterile semantics; as I mentioned to one of the organisers in the pub afterwards, “macroecology” seems to me to be more about a philosophy of approach rather than a field in itself.

Formal teaching has largely finished for the time being, so in addition to research activities and university administrative work, much of the remainder of the last couple of weeks seems to have been taken up with editorial and peer reviewing duties for journals, including PLoS ONE, for which I’m an academic editor. This can be time consuming and thankless, but is absolutely vital if the whole system of scientific publishing is not to grind to a halt. Scientists must write, but that writing is supported by a body of individuals who act as peer reviewers, editors, proof readers, and so forth. Collectively that eats up a lot of scientist-hours and is something we should never take for granted.

The Roof Tiles of Chirche (Darwin’s Unrequited Isle part 3)

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Architectural analogies in evolution are not new. The most famous (and, in its time, controversial) is perhaps Gould and Lewontin’s “Spandrels of San Marcos and the Panglossian Paradigm” in which these prominent evolutionary biologists suggested that some features of the biology of species were secondary “emergent” structures which formed from the conjunction of other, evolved characteristics. That is to say these features are not evolved in their own right, they are simply by-products of the evolution of other factors. In this respect they are like “spandrels” – the ornamented space between two structurally significant elements, for example the arches and the domed roof they uphold in the Basilica di San Marco in Rome. Gould and Lewontin were following a metaphorical path that had been traversed by many major figures in evolutionary biology. Most notably, Darwin used the notion of the architect, contrasting natural with artificial selection, in a number of his books, including “The variation of animals and plants under domestication”.

Another architectural analogy occurred to me over the past couple of weeks, time Karin and I have spent back in Tenerife pursuing field work funded by a small grant from the British Ecological Society. We are staying in a cottage in the pretty village of Chirche in the west of the island. The older properties, our rented castita included, are roofed with traditional, hand made rough clay tiles that are slim, curved and tapering towards one end. Tiles are carefully laid curve up and curve downwards in alternating rows so as to both shield the building from the weather and to shed the rain from the roof in the channels formed by the up-curved rows. These same tiles are used along the ridges of the roof, in contrast to roofing back in the UK where differently shaped tiles would serve for roof and ridge. Not only that but the same basic curved and tapering form serves as a structural element for the tops of walls, as half pipes to direct the flow of water, and as building blocks for chimney stacks, etc.

It’s a wonderful example of economy of manufacture and purpose, using the same basic element to serve multiple functions. What has this to do with biodiversity you ask? It’s a fitting observation for this trip, in as much as we are studying flowers and their visitors. Flowers are another great example of the economy of evolution: all of their basic elements (male stamens, female stigma style and ovary, petals and sepals) have evolved from the same basic botanical element – leaves. If that seems unlikely take a look (a really close look) at some of the fancy, highly bred flowers for sale at your local garden centre or plant nursery. Some will have leaf-like structures deep within the flower where genetic mutations have resulted in the expression of organs rather more like their ancestral form than like stamens or petals.

The purpose of returning to Tenerife is to collect more data as part of an on-going project I’ve been running within our undergraduate field course. The Canary Wallflower (Erysimum scoparium) has flowers that change colour; they are pure white when they first open and from the second day onwards they darken to violet then ultimately purple, staying on the plant for up to 10 days. At the same time the flowers stop producing nectar. The pollinators learn to associate white flowers with more reward and focus their attention on the newly opened blossoms. This is clearly an evolved strategy as it benefits the plant to have its most recent flowers preferentially visited, rather than the older flowers that have already received pollen.

In an earlier paper we demonstrated, by removing purple flowers from experimental plants, that these older flowers act as a long-to-medium range advertisement to pollinators (the plants look purple from a distance). It’s a very intriguing system. We now have about 10 years of data showing that the main pollinator is an endemic solitary bee (Anthophora alluadi). But there seems to be some variation between years, with a wider range of different bee species present in years following very dry winters (such as this one) when there are fewer other plants in flower. So the idea that we are testing is that the relative specialisation of the plant (i.e. how many pollinator species it has) is context dependent: in some years/sites it is a specialist, in others a generalist.

Biodiversity is not fixed in time or space. It varies at all scales and, for this plant and its pollinators, the biodiversity of interactions between them is stable only over modest time periods. Over the millions of years these plants and bees have existed in the Canarian archipelago, their exact roles within the system have probably varied enormously, like actors improvising their parts dependent on the whims of external forces, in this case weather conditions. The roof tiles of Chirche saw little rainfall during the last winter; bad for the local farmers and the other people who depend on this rain. But good for ecologists wishing to study how variation in climate can affect biodiversity.

Darwin’s Unrequited Isle (part 2)

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During our field trip to Tenerife the two vehicles covered over 900km each, which is not bad on an island only about 80 km in length along its main axis. We experienced temperatures that ranged in one day from a few degrees above freezing to the mid 20s centigrade. Up in the laurel forest I mentioned last week the weather was cold and foggy, whilst in the Malpais de Güímar it was hot and dry and we sunburned. We put in long, tiring days of walking transects, identifying, measuring and recording plants, and observing bee and bird behaviour. And there were ticks that had to be picked off skin in one of the barrancos we visited. The Romantic Adventurer within me would therefore like to believe that the aching limbs and upset stomach I suffered when we got back to the UK were due to some exotic virus passed on by these blood sucking arachnids. However the Cynical Traveller thinks it was more likely to be due to a hamburger of dubious age and temperature that I ate at Tenerife Sur airport on the way home.

The Tenerife Field course was hard work but great fun and I think (I hope!) the students learned a lot. At the very least they have now experienced just how diverse habitats can be on a small oceanic island. In that diversity rests both the beauty of Tenerife and part of its scientific interest. This variability in habitats is a result of its altitude (Tenerife is the second highest oceanic island in the world after Hawaii), subtropical latitude, climate, proximity to Africa, and geological history. In a single day one can travel from high alpine habitats, through sub-alpine desert scrub and pine forest, into succulent dominated low altitude desert scrub, back up to laurel forest (a form of subtropical rainforest), as well as distinct deep valley and strandline vegetation.

Add to this the occasional hurricanes and forest fires that tear across parts of the island, not to mention volcanic eruptions, plus the human impact, and it makes for a rather dynamic environment at a range of time scales. These processes probably add to the overall biodiversity, as predicted by the intermediate disturbance hypothesis, plus formation of new land area can select for novel proto-species. It begs the question of whether volcanic oceanic islands are more diverse than their coralline counterparts, which we might expect to be less dynamic environments. Has anyone investigated this? That’s one of the things that keeps my interest in biodiversity going: there are too many questions for a single lifetime.

I’m hoping that “Darwin’s Unrequited Isle” will take off as a new name to refer to Tenerife, replacing the Island of Eternal Spring cliché it currently holds (and shares with Madeira). Especially as many of the days we were there were spring-like only in the sense that they were wholly unpredictable. On the roof of Tenerife, in Las Canadas, our car thermometer registered 3 degrees centigrade at 1100am. And it snowed. I’ve never experienced that at this time of the year. We’ve had torrential rains storms but never snow. In late April. In the “Island of Eternal Spring”. I’m not complaining though, it all adds to the fascination of this most interesting of islands and is why we come back year after year. It’s also better conditions than my colleagues Duncan McCollin and Janet Jackson endured with those students who elected to do field work in Northamptonshire rather than Tenerife. For most of the time we were away it poured with rain back home, turning the drought-imposed hosepipe bans into flood warnings in some places.

Needless to say, the day of the snow was the day we were due to make some observations of bee behaviour. By and large bees don’t like snow and low temperatures ground most of them. So that planned activity was delayed until later in the day when it finally warmed up sufficiently for them to start flying.

This theme of variability in the weather, on a day-to-day basis and compared to previous years, was a recurring one all week. Tuesday was hot, as I recounted in my previous blog. But Wednesday was a huge contrast as we headed up into the cold, wet laurel forests of the Anagas Mountains. It’s always a little chilly on this part of the island due to the prevailing moisture-laden trade winds, but this year was colder and foggier than I can remember. The students collected data on the distribution of plants up a vertical cliff face that we can compare to similar data from another site collected last year. I’m intrigued by the way succulent plant groups such as Aeonium and Monanthes are able to survive on these water limited, nutrient poor environments, vertical versions of the desert scrub lower down the mountains. These succulents add to local plant species richness within the forest and provide nectar and pollen resources when they flower, increasing the overall levels of biodiversity of an already diverse habitat.

As well as studying plant diversity we also did some work with the animals of Tenerife. The bees I’ve already mentioned, but for the first time we also made some observations of how bird behaviour changes in tourist areas compared to more isolated spots. Even within a very short distance, no more than a few hundred metres, it’s clear that bird diversity, abundance and range of observed behaviours were greater in the areas where tourists congregate to barbecue and relax. We did some similar work with lizards for a few years and found that they were bolder close to tourist car stops than further away. Humans can impact the life of this island in very subtle ways.

We also spent a morning with volunteers from the Atlantic Whale Foundation (AWF) on one of their trips out to record individual whale and dolphin activity off the south west coast. The AWF piggy backs on one of the commercial whale watching boats and the students are encouraged to think about the synergies and tensions between the conservation-motivated scientific observation of the AWF and the commercial motivations of the tourist boats. It gets to the heart of what “eco-tourism” is all about and the point at which it does more harm than good. The only strong opinion that I have about it is that the value of eco-tourism is context dependent; some activities are better than others in some circumstances but not others. Regardless, the trip is always popular with the students (except one year when a student spent the whole time aboard with her eyes closed, suffering chronic sea sickness) and this year was exceptional, with great views of bottle nosed dolphins and pilot whales, as well as long distance spottings of common dolphins and a 20m fin whale.

The final day of the trip, prior to getting to the airport, is traditionally spent at the Pyramids of Güímar ethnographic park where the students discover some of Thor Heyerdahl’s left field views about possible pre-Columbian links between Canarian, Mediterranean and New World peoples. Whatever the truth behind the origin and function of these enigmatic structures, the visit is a pleasant way to end the field course. Nestled within the protective bowl of the Güímar Valley, I often wonder if it’s a coincidence that the Güímar structures look out towards the three cinder cones adjacent to the Güímar Badlands. Approaching from the south along the TF1 road, these hills take the form of a heavily pregnant woman lying on her back. Was it of symbolic significance to the ancient Tenerifeans in the days prior to the Spanish conquest? I like to think so though we probably will never know.

A small grant from the British Ecological Society means that I’ll be back in Tenerife at the end of May for ten days to do some follow up field work. Hamburgers will be avoided.