Category Archives: Apocynaceae

We’ve just named a new species of fly from Yemen! And it came out of a flower from Kew

Back in the late 1990s and early 2000s, whenever I had a (rare) day free from teaching, marking, supervision, meetings, writing, and other university commitments, I would hop on the train from Northampton to London. My destination was the Spirit Collection of the Herbarium at the Royal Botanic Gardens, Kew, where bottled flowers are preserved in their three-dimensional complexity, rather than squashed flat onto herbarium sheets. To this day, the smell of formaldehyde in the “Kew Mix” takes me back to the chilly basement space of that collection.

The Kew Herbarium is a massive, internationally important resource for taxonomy, evolutionary biology and ecology, and one which ought to stay where it is, in my opinion.

The purpose of my visits was to exploit the large number of Ceropegia specimens that had been collected by botanists working in Africa, the Middle East, and Asia. These amazing flowers are so complex that they are best preserved in spirit, and that complexity in turn is a function of their sophisticated pollination systems. The flowers temporarily trap their pollinators, releasing them unharmed after a period, during which they will have picked up pollen and/or the flower will have been pollinated. If you have ever grown String-of-Hearts as a house plant, that’s the group we are talking about.

The botanists who collected these flowers were, of course, only interested in the plants. But as well as pickling the blooms they sometimes pickled the insect contents of the flowers, giving us a record of what the flowers were luring into their temporary traps. Not only that, but Ceropegia belongs to the milkweed subfamily of Apocynaceae, which means that their pollen is in the form of pollinia. These are coherent packages of pollen that mechanically, and persistently, clip to the insect. This gives us an opportunity to sort out the real pollinators (with pollinia attached) from other insects that may be inside the flowers for other reasons, such as looking for prey or sheltering from the dry heat of the day.

It had occurred to me that if someone was to check these flowers for insects, and extract any that were found, then we could build up an unprecedentedly complete picture of the diversity of pollinators in a large, mainly tropical plant genus of around 200 species. So that’s what I did, whenever time allowed. Having gained permission to do this, I was pleased to discover that the process was considerably speeded up by the fact that preserving the flowers in this way clears the tissues, making them colourless and translucent. By shining a bench light through the bottles I could see which flowers contained insects and carefully dissect them out.

Most flowers were empty, but occasional visits over a period of a few years resulted in a data set of flower visitors and pollinators for about 60 species and subspecies of Ceropegia. The first paper from that work was published in 2008 in Annals of Botany as ‘Fly pollination in Ceropegia (Apocynaceae: Asclepiadoideae): biogeographic and phylogenetic perspectives‘. Later work by colleagues and myself meant that in 2017 we could publish an update in the journal Flora (Diversity of Diptera families that pollinate Ceropegia (Apocynaceae) trap flowers: An update in light of new data and phylogenetic analyses).

The work also fed into our large study of pollination systems in Apocynaceae and I even published a small note about an ant specimen that I had extracted which still had the evidence of its last meal (a fly’s wing) protruding from its mouth.

The work at Kew had given us a short cut to understanding how pollination systems have evolved in this big plant species radiation. The equivalent field work required to collect the same data would have taken many person years and no funding agency would have given it the time of day. Not only that, but a portion of the data is from parts of the word that are war-torn, dangerous, and largely inaccessible to field scientists at the moment. Which brings us to the present paper.

All of the pollinators, and most of the flower visitors, to Ceropegia that have been discovered to date are small flies (Diptera) often only a couple of millimetres in length. There are relatively few taxonomists who can identify such flies and most of the specimens I extracted were identified to genus or family by Andrew Whittington. One such specimen was determined to be a species of Lygistorrhina, known as ‘long-beaked fungus gnats‘. It was found in a flower of Ceropegia aristolochioides ssp. deflersiana, which is something of a generalist in this genus of specialists: it’s pollinated by at least four fly genera and 11 others have been collected from its flowers sans pollinia, including this one.

The flower was collected in 1975 by botanist John Wood, in Yemen – like I said, inaccessible – and the semi-arid climate in which it was found, whilst typical for Ceropegia, is unusual for Lygistorrhina. When National Museums Scotland entomologist Vladimir Blagoderov looked at the specimen he quickly realised that it was a new species and contacted Andrew and myself to discuss describing it. The paper documenting the new species, which we have named Lygistorrhina woodi in John’s honour, was published today. Here’s the reference with a link to the paper, which is open access:

Blagoderov, V., Ollerton, J. & Whittington A. (2023) A new species of Lygistorrhina (Lygistorrhina) Skuse, 1890 (Diptera: Keroplatidae, Lygistorrhininae) with a key to the subgenus. Zootaxa 5361: 151–158

Here’s the abstract:

A new species of Lygistorrhina (Lygistorrhina) Skuse, 1890, Lygistorrhina woodi sp. nov., is described. The specimen was dissected from an alcohol-preserved flower of Ceropegia aristolochioides ssp. deflersiana Bruyns (Apocynaceae, Asclepiadoideae, Ceropegieae) stored in the Kew herbarium. This is the first occurrence of the lygistorrhine gnats in a hot, semi-arid climate. A key to all known species of the subgenus Lygistorrhina (Lygistorrhina) is provided.

Two of my favourite families, entwined

Introducing Ceropegia stylesii – a novel species of “Brachystelma” from South Africa

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This is a guest post by Dr Annemarie Heiduk about a new species that she’s recently described.

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In an earlier blog post about the discovery of a novel Ceropegia species, Jeff’s finishing sentence was: “I wonder what else is still waiting to be discovered in the stunning grasslands of South Africa?”

I am happy to provide a first answer to this question: Ceropegia stylesii.

This new species does not have the tubular kettle-trap flowers typical of Ceropegia, which temporarily trap pollinators, but open-rotate corollas where the gynostegium (fused male and female reproductive organs) is freely accessible to pollinators. So, in the traditional sense, C. stylesii is not a Ceropegia. This needs some explanation here!

Ceropegia is a genus in the plant family Apocynaceae (Jeff’s favourite family of plants!) and therein the genus is placed in the subfamily Asclepiadoideae which originally was a family on its own (“Asclepiadaceae”).

Within this subfamily, the genus Ceropegia belongs to the Stapeliinae – a subtribe which comprises ca. 720 species. About 220 species thereof have exciting looking and very cleverly designed kettle-trap flowers which attract small flies as pollinators via deceptive strategies (see http://plantlifesouthafrica.blogspot.com/2019/07/plantlife-sa-volume-473-july-2019.html). The remaining species in Stapeliinae are the well-known stem-succulent stapeliads (ca. 355 species in >30 genera) and ca. 140 species known as Brachystelma.

With increasingly better molecular methods to study the evolutionary relationships of species in Stapeliinae, the traditional grouping of the species was illuminated as being artificial, i.e., species with kettle-trap flowers are not actually a natural group and Brachystelma species are scattered among them; the stapeliads are also nested in Ceropegia but as a single (monophyletic) group. These results based on DNA-sequence similarities are not compatible with the traditional generic concept in Stapeliinae, and as a result, changes were instigated.

Some colleagues wish to see all 720 species of Ceropegia, Brachystelma and the stapeliads merged into one single large genus Ceropegia, a solution which would entail more than 400 new name combinations. Others prefer to adopt a less dramatic change of concept and only include Brachystelma in an enlarged Ceropegia while keeping the stapeliads separate based on their monophyly and distinct vegetative features. This pragmatic solution considers both taxonomic and phylogenetic facts and reduces the previously multiple cases of paraphyly to a single case. More importantly, it avoids hundreds of name changes in the group. Both concepts are correct in their own right and justified, so it is a personal decision which one to follow.

The newly described species C. stylesii would traditionally have been placed in Brachystelma as it is lacking tubular kettle-trap flowers. After the inclusion of Brachystelma into Ceropegia, C. stylesii is placed within section Bowkerianae – a group comprising species both with and without tubular kettle-trap flowers. With the description of C. stylesii, the section now has 15 members of which 10 have open-rotate flowers. Among these, C. stylesii appears to be most closely related to C. gerrardii from which it can only readily be distinguished when in flower (see the lower most image above).

The flowers of C. stylesii superficially look like miniature versions of a dark-flowered form of C. gerrardii, which growths in the same habitat. C. stylesii flowers are only about 6 mm in size whereas those of C. gerrardii are about three times larger. While C. gerrardii occurs in grasslands throughout eastern South Africa, C. stylesii is believed to be endemic to Ngome, where it is known from two localities with a total of less than 10 plants. After the recent discovery of C. heidukiae at Ngome, the area revealed another outstanding member of this amazing plant group, and thereby once again proves its conservation importance.

C. stylesii is named for David Gordon Alexander Styles, botanical explorer and collector, to honour his valuable contribution to botanical knowledge in South Africa. David is renowned for “…his daring nature to go leaps and bounds for the specimen he is interested in” (see Chetty 2021), a statement I can readily confirm based on personal experience. Many of David’s collections (by now well over 6000 specimens donated to various herbaria) are novelties awaiting to be described. With C. stylesii, a total of five plant species bear his name. I am delighted that eventually a Ceropegia species could be named for him as David’s knowledge on the distribution and habitats of these special plants is of great value to my research on this plant group.

A new study shows that even short-tubed flowers can specialise on hawkmoths as pollinators

Generating AI art from titles of scientific publications

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WARNING: huge time wasting potential ahead.

As regulars to my blog might know, I’m a sucker for computer-generated “stuff”, for example virtual ecological systems; see my 2020 post “a simple online ecosystem model: like Tamagotchi for the green generation“. Last night while browsing Twitter I came across a few people tweeting about app.wombo.art which uses words and phrases as a prompt for its AI to generate art in a variety of styles. For example, the image above is based on the title of my book Pollinators & Pollination: Nature and Society. The downloaded image always has “dream” at the top which is easy enough to crop, while “PROMPT” is the word or phrase that you entered, which can be turned off.

You can also use the titles of scientific articles – this one is my 1996 paper “Generalization in Pollination systems and Why it Matters” (I don’t think that it counts as a graphical abstract…):

A lot of people were submitting their thesis titles and I expect to see some of these used as frontispieces in PhDs in the near future. Here’s mine (from 1993) – “Ecology of flowering and fruiting in Lotus corniculatus“:

The other category that I had fun with was using scientific names – here’s the genus Ceropegia:

And here is Apocynaceae:

Can you guess what phrase I used to generate this one:

What’s really fascinating about this system is that every time you generate an image from the same phrase it returns something different. Go have fun, but be warned: it’s a bit of a rabbit hole and it’s possible to waste a lot of time playing around:

A milkweed on the shore: tracking down an elusive Danish plant

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Since arriving in Odsherred towards the end of August I’ve been looking out for one plant in particular on our bicycle rides and hikes around the region. Vincetoxicum hirundinaria is a widespread asclepiad or milkweed: a member of the family Apocynaceae, subfamily Asclepiadoideae. This is a group of plants on which I’ve published quite a few research papers and which feature heavily in my book Pollinators & Pollination: Nature and Society.

So far the species has proven elusive and a few Danish ecologists that I’d spoken with told me they had never seen it in the wild. The GBIF account of the species shows a few populations in this part of Denmark but I wasn’t sure if they were old records of populations that no longer exist. But as of yesterday I can confirm that at least one of those populations is extant!

We had cycled out to the small town of Klint about 13km west of us, to see the glacial moraine landscape for which the area is famous and which gives Odsherred UNESCO Geopark status. As we approached the small fishing harbour at Klint I let out an excited shout to Karin who was just ahead of me: in amongst the roadside vegetation I’d spotted the distinctive and immediately recognisable yellow of Vincetoxicum hirundinaria in its autumnal hues! In the photos that follow you can see how well that yellow stands out against the colours of the other plants in the community.

At this time of the year the plant has ceased flowering, but the occasional swollen green seed pod was evidence of successful pollination of their morphologically complex flowers.

I was surprised at just how close to the sea the plants were growing; they must get inundated by sea water during stormy tidal surges.

So what is pollinating these flowers on this exposed shoreline? That’s a question that I want to pursue in the coming years. The Pollinators of Apocynaceae Database has remarkably few records of pollinators in this species, given how widespread it is. Flies certainly pollinate it, but there’s also records of wasps and bees as visitors, including bumblebees on flowers of a plant that I had in cultivation in Northampton. There’s a couple of other research groups in Scandinavia and Europe who are looking at the pollination ecology of the species and I’m hoping that we can collaborate on a study of spatial variation in its reproduction. Vincetoxicum is quite a large genus (around 150 species) and only around 10% of the species have been studied in any detail. But these studies are revealing a complex diversity of pollinators, including most recently, cockroaches in the Chinese species Vincetoxicum hainanense. I’m sure this intriguing group of plants has more fascinating stories to tell us about the ecology and evolution of its pollination systems.

FIGURE 4 from Xiong *et al.* (2020) Specialized cockroach pollination in the rare and
endangered plant *Vincetoxicum hainanense* in China. *American Journal of Botany* 107:
1355–1365.

The largest West African flower: Pararistolochia goldieana!

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Some years ago, browsing in a second hand bookshop, I happened across a copy of an old magazine from 1950 called Nigeria. Published by the then colonial government, it was a miscellaneous collection of articles about the culture, geography and natural history of that fascinating West African country. Although aspects of the contents are problematical by modern standards, I bought it because of a short article about a wild plant with enormous flowers and a remarkable pollination strategy. In particular, the spectacular photograph of a man holding a flower that’s the length of his forearm grabbed my attention: who couldn’t love a flower like that?!

The plant is Pararistolochia goldieana, a vine found in the forests of this region, as described in the introductory text:

These types of flowers are pollinated by flies, a common strategy in the Birthwort family (Aristolochiaceae) to which the plant belongs. This strategy of fly pollination in which flies are deceived into visiting the flowers by their stink and colour, and temporarily trapped in the enclosed chamber, is something that I explore in detail in my book Pollinators & Pollination: Nature and Society, particularly in the genus Ceropegia. Those plants show convergent evolution with the pollination systems of Aristolochiaceae, though they are unrelated.

Pararistolochia goldieana has a wide distribution across West Africa, including Cameroon, Equatorial Guinea, Nigeria, and Sierra Leone. The IUCN Red List categorises it as ‘Vulnerable’ due to habitat loss. The population where these photographs were taken is described on the final page of the article:

The city of Ibadan is one of the largest in Nigeria and has grown enormously, ‘from 40 km² in the 1950s to 250 km² in the 1990s‘. I wonder if this forest, and its botanical treasures, still exists?

During field work in Gabon in the 1990s I was fortunate enough to encounter a species of Pararistolochia in the rainforest of Lopé National Park. It was a different species to P. goldieana, with rather smaller but no less spectacular flowers, and it stank to high heaven! We knew it was there long before we saw it. I collected some flies from the flowers and had them identified, though I’ve never published the data: it’s available if anyone is working on a review of pollination in the family.

This 1950 article is anonymous, so I don’t know who to acknowledge for the amazing images. However the botanist R.W.J. Keay was working on a revision of the family for the Flora of West Tropical Africa project at the time, so it may have been written by him.

A spectacular new plant has been named to honour a colleague: meet Ceropegia heidukiae!

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Finding organisms that have not previously been described by scientists is not unusual; every year, hundreds of ‘new’ species enter the taxonomic literature, a testament to how little we still understand about the Earth’s biodiversity. The majority of these species are insects, because that’s the most diverse group of organisms on the planet. But new species of plants and fungi also turn up regularly: for example in 2020, botanists and mycologists at Kew named 156, including some from Britain.

So although discovering undescribed species is not uncommon, any field biologist will tell you that it’s an exciting moment to spot something that you’re never seen before and which could turn out to be new. That was certainly the case when my colleague Dr Annemarie Heiduk’s attention was drawn to a South African plant that was clearly something special. As Anne said to me this week:

‘I will never ever forget the very moment when I spotted it and immediately knew it was something no-one has ever seen before. And I was so lucky to find it in flower. I cannot describe how beautiful it looked sticking out of the surrounding grass vegetation. It is certainly one of a kind and I really know how lucky I was to have found it. Not once did it ever cross my mind that I will discover a novel Ceropegia species, let alone one that is so distinct!’

So it was that last year Anne discovered the plant that was to be named in her honour: Ceropegia heidukiae. The species has been described by David Styles and Ulrich Meve in the journal Phytotaxa (from where the image above was taken). There’s also an account of the species on the Pollination Research Lab blog, with further photographs and information about the plant.

Anne has been honoured in this way not just because she discovered the plant, but also because, to quote the paper, she:

‘is a pollination ecologist who with her research on the floral chemistry and deceptive pollination strategies of Ceropegia trap flowers has acquired recognition as an expert in this field’

Anne tells me that she has already collected pollinator and floral scent data for this new species, so we can look forward to seeing that published in the near future. I described the fascinating pollination ecology of Ceropegia, including some of Anne’s earlier work, in my recent book. This is a genus of plants that has intrigued me since I first saw photographs of them and started growing them as a teenager, 40 years ago. Since then I’ve published several papers about their pollination strategies, and how they compare with the family Apocynaceae as a whole: see the following links for some examples:

https://jeffollerton.co.uk/2017/09/03/fly-pollination-in-the-trap-flower-genus-ceropegia-a-new-study-just-published/

https://jeffollerton.co.uk/2018/08/21/the-evolution-of-pollination-systems-in-one-of-the-largest-plant-families-a-new-study-just-published-download-it-for-free/

So, a big congratulations to Anne, and to David and Ulrich – it’s an amazing plant! I wonder what else is still waiting to be discovered in the stunning grasslands of South Africa?

Flowers can be assholes – quite literally!

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WARNING: There’s a high yuck factor to this post, it’s not for the squeamish or easily offended!

One of my Twitter contacts, Traci Birge in Finland, has been reading Pollinators & Pollination: Nature and Society, and making some very nice comments about it. I had to laugh at this one in which she describes some plants as “assholes” because of the way in which they deceive pollinators into visiting their flowers but offer no reward in return:

Pollinators and Pollination is a great journey.

Still thinking about plants manipulating animals – plants can be assholes (@JeffOllerton's description is more scientific), e.g. using scent to convince flies they are carrion & suitable site for egg-laying.
— 🐟 Traci Birge🐝 (@TraciInFinland) January 17, 2021

If you follow that thread you can see that Traci was closer to the truth than perhaps she realised: there are some plants with flowers that appear to mimic the anuses of dead mammals, particularly in the families Apocynaceae and Araceae. By their smell, texture, colour and hairiness they are fooling flies into visiting the flowers, because assholes, like any mammalian orifice, provide an entry point for maggots of carrion-feeding flies. Sometimes the deception is so great that the flies lay their eggs on these blooms, though of course the maggots starve.

A great example of an anus-mimicking bloom is the Dead Horse Arum (Helicodiceros muscivorus). Check out the image above: if that doesn’t look like a horse’s ass, I don’t know what does!

Other examples might be found within the stapeliads, especially the genus Huernia which often have a thickened annulus to the centre of the flower. However that could also be interpreted as mimicking an open, inflamed wound on the side of an animal:

As I point out in the book, you might imagine that there would be strong natural selection against flies visiting these flowers if they lose fitness by laying eggs on such an unsuitable substrate. But the flowers are tapping into really deep-seated behaviours and clearly the flies can’t distinguish the flowers from the real thing.

This is flower pollination that is far removed from the deliciously perfumed, cute-and-cuddly, heart-warming world of bees and flowers. Isn’t nature wonderful?

All photos from Wikipedia, as follows:

Helicodiceros muscivorus: Göteborgs botaniska trädgård (photographer: Ingemar Johansson) – http://www.mynewsdesk.com/se/pressroom/goteborgs_botaniska_tradgard/image/view/dracunculus-muscivorus-128973, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=19265330

Huernia zebrina: Enzo^ – Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=10963668

Huernia schneideriana: Juan Carlos Fonseca Mata – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=94705877

Cockroaches as pollinators: a new example just published

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When you think of the word “pollinator” what comes to mind? For most people it will be bees, particularly the western honeybee (Apis mellifera). Some might also think of hoverflies, butterflies, moths, bats, hummingbirds…..but cockroaches?! The first published example that I know of which demonstrated that the flowers of a plant are specialised for cockroach pollination is from the mid-1990s. Since then only a handful of well documented cases have come to light, but there are undoubtedly more out there waiting to be discovered, particularly in the wet tropics. Most of the c. 4,600 species of cockroaches are nocturnal, and cockroach-pollinated flowers tend to open at night, which is one reason why they are under documented.

In a new study, published this week in the American Journal of Botany, a team of Chinese, German and British biologists has shown that a species of Apocynaceae from China is the first known example of cockroach pollination in that large family. Here’s the reference with a link to the study; if anyone wants a copy please email me:

Xiong, W., Ollerton, J., Liede-Schumann, S., Zhao, W., Jiang, Q., Sun, H. Liao, W. & You, W. (2020) Specialized cockroach pollination in the rare and endangered plant Vincetoxicum hainanense (Apocynaceae, Asclepiadoideae) in China. American Journal of Botany (in press)

The abstract for the paper follows:

Premise

Species of Apocynaceae are pollinated by a diverse assemblage of animals. Here we report the first record of specialized cockroach pollination in the family, involving an endangered climbing vine species, Vincetoxicum hainanense in China. Experiments were designed to provide direct proof of cockroach pollination and compare the effectiveness of other flower visitors.

Methods

We investigated the reproductive biology, pollination ecology, pollinaria removal, pollinia insertion, and fruit set following single visits by the most common insects. In addition, we reviewed reports of cockroaches as pollinators of other plants and analyzed the known pollination systems in Vincetoxicum in a phylogenetic context.

Results

The small, pale green flowers of V. hainanense opened during the night. The flowers were not autogamous, but were self‐compatible. Flower visitors included beetles, flies, ants and bush crickets, but the most effective pollinator was the cockroach Blattella bisignata, the only visitor that carried pollen between plants. Less frequent and effective pollinators are ants and Carabidae. Plants in this genus are predominantly pollinated by flies, moths and wasps.

Conclusions

Globally, only 11 plant species are known to be cockroach‐pollinated. Because their range of floral features encompass similarities and differences, defining a “cockroach pollination syndrome” is difficult. One commonality is that flowers are often visited by insects other than cockroaches, such as beetles, that vary in their significance as pollinators. Cockroach pollination is undoubtedly more widespread than previously thought and requires further attention.