Tag Archives: Botany

6000 scientists can’t be wrong: the International Botanical Congress 2017

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A late afternoon flight from Heathrow got me to Beijing International Airport just in time for me to enjoy a nine hour delay in my connecting flight to Shenzhen in southern China.  I finally arrived at my hotel at 2:15am, exhausted and sweaty in the 30 degree night time heat.  The one consolation is the the hotel was short of rooms so upgraded me to a suite the size of a small city, with a shower like a tropical rainstorm.  Perfect to wash off the dirt of travelling before collapsing into bed.

Why am I here and why is the hotel short of rooms?  Because 6000 scientists have descended on Shenzhen for the 19th International Botanical Congress (IBC).  The IBC is a six-yearly event that rotates around the world; I attended in 1999 in St Louis and 2005 in Vienna, but missed Melbourne in 2011.  At this IBC I’m giving two talks, one at the beginning and one at the end of the conference.  More on that later in the week.

Six thousand botanists need a big conference venue and this morning, after a late breakfast, I strolled up to the convention centre where it’s being held.  It’s enormous, the scale of the thing is overwhelming.  I wandered around whilst they were getting ready for registration opening this afternoon and took some images on my phone.

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There are some fabulous displays of living plants, including this one at the main entrance:

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These are attracting pollinators: in 10 minutes I counted lots of honey bees, one butterfly, at least two species of wasps, and a large carpenter bee (Xylocopa sp.) visiting flowers.  I only managed to photograph the first two though:

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On the way back to my hotel I gatecrashed an international turtle expo.  Who knew turtles were such a big thing in China….?

OK, that’s all for now: I have to head back to the convention centre to register, so I’ll leave you with the view I’m seeing from where I’m writing this.  Shenzhen is quite a place and I’ll write more about it later in the week:

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Filed under Bees, Biodiversity, Butterflies, Honey bees, Pollination, Urban biodiversity, Wasps

Dispelling the myth that orchid species usually only have a single pollinator

Orchids at Kew 2014-02-24 15.30.32

The idea that members of the plant family Orchidaceae (the orchids) “typically have exclusive relationships with their pollinators“, such that each orchid has only one pollinator, is a persistent one.  Recently I’ve encountered it on horticultural websites (follow that last link), in grant proposals, and on Wikipedia.

The problem is that it’s not true: it’s a myth that is perpetuated by people (often botanists or horticulturalists) who may know a lot about orchids but don’t know as much as they think they know about pollination ecology.

Orchids certainly have some fascinating and often quite intricate floral mechanisms to ensure pollination, but these have not necessarily evolved to attract and exploit just one species of pollinator.  Even in the case of sexually deceptive orchids that fool their (male) pollinating insects into believing that they are mating with a female of the same species, it is sometimes the case that more than one insect species is involved.  For example, in the well studied genus Ophrysflowers are pollinated by a narrow taxonomic range of pollinators, from a single species to up to five closely related species“.  As the authors of that last paper state, this is not the same as the mythological “extreme case of one orchid/one pollinator”.

Likewise different species of orchid bees may pollinate the same orchid flowers as they visit to collect scent compounds; for example in the Brazilian species Dichaea pendula, species from at least two different bee genera act as pollinators (Nunes et al. 2016).

The fact that “one orchid/one pollinator” is a myth is not new knowledge, it’s been widely discussed in the pollination ecology literature for decades.  For example, in our 1996 paper “Generalization in Pollination Systems, and Why it Matters” we showed data from the late 19th/early 20th centuries that clearly indicated a range of specialization in European orchids (follow that link and look at  Figure 3B).  Even earlier than this, in his 1992 paper “Trends in the pollination ecology of the Orchidaceae: evolution and systematics” Raymond Tremblay showed that only about 62% of species for which he could find data had a single pollinator, and that this varied considerably between different subfamilies of Orchidaceae, with some subfamilies being more specialized than others.

More recently, in a chapter in the 2006 book I co-edited with Nick Waser entitled “Geographical Variation in Diversity and Specificity of Pollination Systems” Steve Johnson, Andrew Hingston and myself looked at data from southern African compared to North American and European orchids; here’s the figure from that assessment:

 

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Orchids  are more specialized in southern Africa compared to Europe and North America (as are a number of other plant groups including the asclepiads, which we’re comparing them with here).  But even in southern Africa, only about 65% of the orchids studied have a single pollinator species.  It’s worth pointing out, though, that many of the species included in this analysis, and in Raymond Tremblay’s paper, have been studied only at single sites and often in single years, meaning that we have no idea if there is any spatio-temporal variation in the pollinators a particular orchid species exploits.

Why does this myth persist?  I think it’s for the same reason that myths are retold from generation to generation: they are great stories that fascinate the teller and the audience.  Indeed, orchids are very special plants with some amazing floral and vegetative adaptations, fascinating relationships with fungi, and incredible diversity.  But we don’t have to mythologise their relationships with their pollinators to try to make orchids more special than they already are.

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Filed under Bees, Biodiversity, History of science, Pollination

What’s green, waxy and smells of cheese? The flowers of Deherainia smaragdina!

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A tweet this morning from Chris Howell at Birmingham Botanical Garden reminded me that for some time I’ve been meaning to post up images of an enigmatic flower that has intrigued me for over a decade, ever since I encountered it in the Palm House at Kew.

It was the smell that I first noticed: strong and pungent like a ripe blue cheese, or unwashed feet.  This drew me to a small, evergreen shrub with the wonderfully eliding name of Deherainia smaragdina, a Mexican member of the primula family (Primulaceae) though older sources put it in the Theophrastaceae, a family no longer recognised by most botanists.

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At first I couldn’t spot where the smell was coming from, then I saw the flowers: larger than I was expecting (a couple of centimetres across) given that they were not immediately obvious, and very waxy and stiff to the touch.  In fact (to the human eye) it was quite well camouflaged against the plant’s own leaves, not at all what one expects from a flower.  However camouflaged flowers that rely only on scent for attracting insects are not unknown in the plant kingdom, and probably under-recorded: see for example Adam Shuttleworth and Steve Johnson’s work on wasp-pollinated flowers of asclepiads (Apocynaceae) in South Africa, where the “cryptic colouring” is similar in reflectance to the background vegetation.  “Smaragdine” means emerald-like, so a very fitting species name.

The scent tends to come and go, perhaps affected by temperature or light levels.  Under the scanning electron microscope the surface of the petals has some intriguing bulbous cells (which I’d hypothesise produce the scent) and the wavy, waxy covering of the cuticle is clearly visible:

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Another intriguing thing about Deherainia smaragdina is that the bisexual flowers are in a male phase when they first open, moving into female phase only after a day or two. Compare the two flowers below.  In the male phase (left) the pollen-bearing stamens are centered in the flower, hiding the female stigma (which is probably not receptive at this stage); over time the stamens move outwards to expose the stigma and the flower goes into female phase (the flower on the right):

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Why this plant should smell of cheese is a mystery, but it’s probably attracting a particular type of pollinator – though what they are no one knows !  It’s never been studied, as far as I’m aware.  We might predict from the scent that it’s flies, but I think that wasps are also a possibility.  If anyone is doing field work in the parts of Mexico where this plant grows, please look out for it and try to photograph flower visitors: I’d love to hear from you!

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Filed under Biodiversity, Pollination, Wasps