Spirits of the ancestors: the evolution of spurges

Some new spurge discoveries this week:  a species new to me, and some insights into where these weird weeds came from.   There’s a reconstruction of the supposed ancestral spurge,  and a draft family tree, some of whose branches have criss-crossed the Atlantic.  It may be long, but these plants tell an amazing story about our planet.

The latest spurge I found,on Boxing Day, was growing on a sunny bank near the Etang de Thau, and fittingly it’s called Euphorbia helioscopa [sun-watcher], sun spurge in English, Euphorbe réveil-matin, or Petite éclaire in French. All because the umbels open and face the sun in the morning.

Euphorbia helioscopa

The characteristics by which you can identify it include these: the leaves are oval, wider above the middle and finely toothed, red-tinged as is the stem; it has a flat terminal inflorescence consisting of a five-rayed umbel, and kidney-shaped nectar glands.

Another discovery this week was the website of an Italian naturalist, Dr Giuseppe Mazza, who describes in a fine style  the way the capsules of this species split open explosively, like most Euphorbias, to disperse the seeds: ‘And during a quiet autumn afternoon, between the herbs of the orchard, we can easily hear, as well as see, the babies of the Euphorbia helioscopa leaving for conquering the world.’

I do recommend a visit to his site, photomazza (click here). In a long translation of his article on Euphorbias he says the flowers are heirs ‘of the ancient bisexual corollas of a wicked botanic ‘Dynasty’…where poison, castration and nudism are of the family’.  Doesn’t sound like the textbook I had for A level.

Now for evolution, and there are a couple of important bits of background.  First, understanding something of the movement of the continents on their tectonic plates is vital to understanding how older plant forms have evolved: plant communities get separated and evolve in different directions, and get carried into new climate zones which exert new selections of the fittest. But it is like trying to understand three-dimensional chess. Try this video to get a general idea – I think it’s stunning, 600 million years in 90 seconds:

There’s also a good sequence of maps here.

Most diversity in the Euphorbiaceae family is in southern and eastern Africa and Madagascar, and most species are in tropical or subtropical Africa  and South America. In general, greater diversity indicates greater age of a group of plants. This suggests a possible origin for the family in the South Africa part of the supercontinent Pangea (Gondwana in the map below), and a spread to the part which would become South America.

Pangea 152 million years ago

Pangea – shown above when there were just ferns and pines,no flowers – had finally broken up by about 100 million years ago, when South America split off from Africa and the South Atlantic began to widen (below). This theory of  the origin of these plants is borne out by molecular studies, and the few fossils we have, which give an estimated age for the Euphorbiaceae family of 114 million years – in other words, very, very old : flowering plants only began to evolve about 140 million years ago.

Pangea 94 million years ago

(Colour maps from scotese.com)

Now the second bit of background.  The study of evolution has been revolutionised in the last few years by molecular genetics – the analysis of plant DNA to find particular genes or markers, and then comparing several species to see which has what.  The more genes in common, the more close the relationship, and a gene common to all suggests an ancestral feature. In this way a family tree can be drafted, and even dated – because we can estimate the rate of change in genes through mutation.   I found a recent (2012) molecular study of Euphorbia,  and if you’re not put off by a bit of jargon, it’s worth a look for the pictures and diagrams, though the middle section gets way too technical for me (you can find it here) .  Scientific papers are a bit like gunpowder tea: dry and shrivelled at first sight, but the longer you let them soak in your mind, the more flavours they release. Basically, from looking at the distribution of 10 genetic markers over 176 species, this is what the researchers come up with:

The Euphorbia genus can be divided into four big groups,  or clades in botan-ish. One of these, called the Esula clade, contains 500 species found in temperate regions of the northern hemisphere, from the eastern Mediterranean to central  Asia .  This group are almost all herbaceous, with a straight, leafy unbranched shoot and a terminal inflorescence.  It contains all the wild species I see here, and the other European species.

Let’s take a break to look at one of these: Euphorbia serrata.   It has leaves with finely toothed margins, and which become broader higher up the stem.  The umbels have 3-5 rays, and the bright yellow bracts are wide – the inflorescences make quite an impact.

Euphorbia serrata in May

The other groups seem to have developed successively in evolution from this stock, and comprise a group of 200 xerophytes (dry-adapted species) in South Africa; a group of 700 different species in Africa and Madagascar; and a group with half a dozen African members and about 600 species in the New World (including Poinsettias). The similarities in the last group suggest an early African origin and some evolution there, followed by ‘a single dispersal event’ to the new climates of the New World, where variation ran wild.  Now it seems that the Euphorbia genus evolved about 42.5 million years ago, long after South America had sailed away on its tectonic plate. So how did Euphorbia cross the ocean?

We don’t really know. To get there like humans did, through Asia and over the Bering Straits to Alaska, would have involved crossing inhospitably cold climate zones. Humans could dress up warm, plants can’t. So it has been suggested that there was a land bridge between northern Scotland and Greenland, and then to Baffin Island, about 40 million years ago when these regions were much warmer than they are now. Also, they were then, and are now, much further south than Alaska. Other genera in Euphorbiaceae, such as Croton, had evolved in America from the original 100 million-plus year old stock, but seem to have spread eastwards to Europe at about the same time. The land bridge had gone by 35 million years ago.  Could plants travel so far in the time available? Think of it: if seeds disperse a metre a year, that’s a kilometre in 1,000 years, 1,000km in a million. One thing geological time has got plenty of is time.

Now for the reconstructed ancestor-spurge of around 42 million years ago in Africa: it turns out that these most resembled the Esula clade, in other words the kinds of Euphorbia I’ve been featuring.  It was a non-succulent, woody plant with leaves arranged in a spiral around the stem, and cyathia in terminal inflorescences. The basic plan was probably for five of each flower part – now reduced to three compartments in the ovary of the female flower, a single stamen in the male flower, and commonly four nectar glands. The family forebears before this were probably wind-pollinated, with separate groups of male and female flowers on each plant: as Euphorbia evolved from this the flowers moved closer and the bracts became petal-like, and nectar glands developed, to form the cyathia  (unique to Euphorbia) which could attract insects – these weren’t around when the Euphorbiaceae family started over 100 million years ago.

Molecular genetic studies show a slow and steady rate of evolution in the Esula clade, as species arose to adapt from the subtropics to the increasing extent of areas in the northern hemisphere with temperate conditions,including cold and dry seasons. The poisonous milky sap is an adaptation to deter herbivores which were common in temperate grasslands.

Further, these genetic studies show that xeromorphic features in the genus as a whole, such as spines and succulence,  have evolved on at least fourteen separate occasions over the last 40 million years: an outstanding example of parallel evolution.

Well done for getting this far. A final photo call for Euphorbia cyparissias, or cypress spurge, so named for the many stems whose slender leaves look like young pine shoots  – the photo was taken back in May last year.

Euphorbia cyparissias in May

Euphorbia is such a rich genus, and carries the traces of 40 million years of the history of our planet, its continents and its climate. The more we study it, the more it has to tell us.

I’ve been trying in the music selections for these last three posts to mirror the way these species have travelled out of Africa, and through Europe to America, and back again, sometimes coming up with the same innovations in different places.  In the first was Sun Ra, who claimed to have been born on Saturn, but in fact came from Birmingham, Alabama, and who used imagery and costumes from Egypt. Second, Randy Weston who  came from New York, but lived and worked for many years in Morocco. Today’s choice is the Ethiopian  Mulatu Astatke, who was educated and began his career in Britain and then New York, before returning to his native country. He’s made some wonderful recordings in the last few years, and from the highly recommended album Mulatu Steps Ahead (2010) here’s a live version of an appropriate title: ‘Motherland’. On trumpet is the American-born British resident Byron Wallen. You can’t pin a good musician (or plant) down.

Coming up next: the ‘Kewdunnit’. More of a ‘whydunnit’, as you’ll see.

 

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First International Name-That-Spurge Competition: the finals

There’s a definite thrill in the herbarium as French, Occitan, Swedish, Algerian and English teams take their places. The Latin team is elderly, but a strong contender. There’s even a lone Italian. And what’s more, every competitor is clean: no steroids, no EPO, no diuretics. Why am I so sure? Well, this is botany,not professional cycling, and furthermore the whole thing is of course completely imaginary.

Euphorbia segetalis in the vines

Here for starters is the spurge that’s been lighting up the vineyards (if not the sports headlines) for a few months now:  and the Latins are off the mark with Euphorbia segetalis, or field spurge.

Euphorbia segetalis in December

Its leaves have fallen and the pink stem holds a yellow flowering and fruiting head, sometimes ball-shaped, usually slightly flattened.  The French team call it Euphorbe des moissons (harvest spurge), from its late flowering, and the Occitans lo lantreson, a contraction of the Latin lacteritia or milk-yielding.

Other Occitan names, applied to various species , include lo marcivol, which is derived from the Latin marcere, to wither or fade(marceribilis= liable to wither)  –  I presume because of the blue- or grey-green colour of the leaves, or because the flowers have no petals, as if they have already dropped.  Also la lachuscla, from lach (milk) and usclar (to burn) – this is worth remembering since the sap is irritant to the skin, sometimes severely so, and can cause blindness if it gets in the eyes. If you’re weeding it in the garden, or pruning any Euphorbia species, wear gloves and don’t touch your eyes. This property means it has been used in traditional medicine for warts and skin cancers. In the middle ages the irritant leaves were used by beggars to produce unsightly sores on their skins, with a view to eliciting more pity and more money from passers-by. Extra points to the Occitans for being safety-conscious.

How are the teams shaping up so far? I must admit I’m a bit disappointed by the Occitan vocabulary here.  Since the plants are all known to be strong purgatives (spurge is from the Latin expurgare, via old French espurge), I was expecting a variety of shit-related names, a cacophony of caca. In fact there seems only to be one: for the caper-spurge (E. lathyris) there is catapuça (catapuce in French) from  the Italian cacapuzza, or shit-stink.  In Chaucer’s Nun’s Priest’s Tale, ‘katapuce’ is one of the ‘laxatyves’ recommended by the hen Pertelote for the cockerel Chauntecleer to rid him of the indigestion which is giving him frightening dreams: ‘To purge yow bynethe and eek above’. The large fruits of this species were taken like pills in the 14th century.

Euphorbia characias in May

Let’s try another round. Here is E. characias (Mediterranean spurge) easily recognised because it’s one of the tallest spurges, often over a metre high, and because it has violet-brown nectar glands.

E. characias close up – note the brown nectar glands

For some reason, in Occitan it has the feminine version of the same name as the previous spurge: la lantresa, so for unoriginality the team lose the extra points they just gained.

So far the inter-language naming competition hasn’t really taken off: French and Occitan are being descriptive and everyone’s still hanging around nervously outside the privy door.  But now here’s an unusual joint effort from the Algerian and Swedish teams. How so? Let me – like all good sports commentators – profile the team by telling you the background story.

It all started in 40BC when Cleopatra VII of Egypt and Mark Antony had twin children, named Cleopatra Selene [moon] – or Cleopatra VII – and Alexander Helios [sun]. It was all looking so good for little Cleo – her famous mother’s only daughter – when at the age of 6 she was made ruler of Cyrenaica and Libya.  However in 31BC her daddy was defeated by Octavian’s fleet at the battle of Actium, and within a few months both her parents had committed suicide. Octavian took the children back to Rome, where they were paraded in golden chains too heavy for them to be able to walk. The twins were given to Octavian’s sister Octavia Minor to raise – she had once been Mark Antony’s wife.  Pick the family dynamics out of that one.

Coins depicting Juba (L) and Selene (R)

Sometime after her 14th birthday Cleo Selene’s  twin brother had died, and she was married to the exiled African king Juba II.  They were sent to rule over Mauretania, present-day Algeria, where Rome needed a client power.  At some point Juba became ill and was successfully treated by a herb collected in the Atlas Mountains by his personal physician – the grateful monarch named the herb Euphorbia regisjubae after the doctor, whose name was Euphorbus, and of course after himself (it is now named Euphorbia obtusifolia ssp regis-jubae.  Juba is said to have written over 50 books, some of them works of natural history.

Euphorbia obtusifolia ssp regisjubae

All so confusing for newcomers to our sport who translate the Greek Euphorbia as ‘good forage’, which is its literal meaning, but which is obviously wrong for a toxic plant.  The Swedish contribution came in 1753 when Linnaeus used the name Euphorbia for the whole genus of similar plants – the full story and much more is on the EuphORBia site here. If you’re an incurable romantic who just wants to know if Juba and Cleo were really in love, you’re reading the wrong blog: try this one  here.

Sorry about the digression – I think the judges might penalise this team for time-wasting. But from now on I’ll look at a spurge, recall Cleopatra, and call the flowers a name that hasn’t – as far as I know – been used yet:  sun and moon, in honour of the twins.

But look who’s limbering up now! It’s time for the English countryman’s team to enter, trained at a secret hideout by their Head Coach Geoffrey Grigson.  In The Englishman’s Flora, Grigson records a fantastic range of names for spurges used in various English counties – I was alerted to these linguistic riches by this entry in a fascinating photo-a-day journal by a writer who often comments here. These names include:  the devil’s cups and saucers (my personal favourite), wolf’s milk , deer’s milk,  virgin mary’s nipple (but giving emetic milk – an anti-mariolater at work here?), devil apple tree, devil’s churnstaff, wart-weed, bible leaf, potatoes in the dish, and Kiss me Dick (I can’t explain this, but I thought you’d want to know). A sensationally poetic performance which puts the yeomen in line for the gold medal.  While we await the adjudication, you might want to read this article by Richard Mabey on species naming –click here.

In a return to the classic boy-meets-girl, boy-pollinates- girl-with-aid-of-insect theme, here are some photos of male and female Mercurialis annua (annual mercury) plants – mentioned in the last blog post.  This habit of single-sex plants is an adaptation to ensure cross-pollination. Male and female side by side: male has the erect inflorescence, female flowers well-nigh hidden.

Mercurialis annua – male (L) and female (R)

Flowers in close-up: male has the stamens:

Male Mercurialis annua

the female flower isn’t obvious, but you can make out a bristly fruit.

Female Mercurialis annua

Music which pays tribute to the traditions of north Africa: the great Randy Weston.

Coming next: the last in the present spurge series.

 

 

 

 

 

 

 

Weird weeds: Euphorbia

Clump of Euphorbia paralias in the dunes

I’ll admit that I’ve put off starting to write about spurges (Euphorbia), partly because I feel I don’t know enough about them, but it’s time to take the plunge.

They are such curious plants, as if assembled on another planet from a description given over a dodgy radio link from a non-botanist on Earth (I’ll say what I can about their evolution in a later post). They’re deeply weird and I’m fascinated by them. Let me list some of their oddnesses.

1.They seem to be flowering plants without flowers  –at least, without petals.  In fact the flowers are very small and rudimentary and the place of petals is sometimes taken by coloured  leaves, e.g. in poinsettias (botanical name Euphorbia pulcherrima,or ‘very pretty spurge’), or by small bracts. Male and female flowers are separate – not a unique feature, but unusual. The nectar glands are sometimes as big as the tiny flowers.

Diagram courtesy of the EuphORBia project website – address below

2. Their whole growth habit is odd – a spurge is like a succulent plant, often hairless and smooth to the touch, as if half plant and half animal – a reptile maybe, or as if made of some new plastic. Most Mediterranean species consist of a tall pinkish stem circled by simple stalkless glaucous (grey-green) leaves and crowned by a complicated inflorescence.

3.They are closely related to plants varying wildly in form: round succulent stems the size of baseballs, spiny succulents resembling cacti, spiny bushes, even trees. Is it in spite of, or because of, all these oddities that they’re so successful? The Euphorbia genus contains over 2,000 species – the second-largest genus in botany. The family Euphorbiaceae comprises at least 7,500 species.

4. They exude a white sap if cut, which contains toxins which are violent purgatives, hence the name ‘spurge’. The origin of the name of the genus is interesting, but I’ll leave it to next time or we’ll be here all night.

Such a lot to say – for this post I’ll just show a species I saw recently, and a close relative from the same family but a different genus.

So, let me introduce you to the sea spurge – Euphorbia paralias  – a perennial, often found growing in clumps in sand dunes, like this one. In fact most spurges prefer dry, sandy or rocky soils, in full sun.

You can see the simple stem and leaf arrangement – it’s characteristic of this species that the leaves overlap, giving it a sort of bottle-brush appearance.

In December when the photo was taken the flowering was over but you can see the fruit, a three-lobed capsule as in all spurges – a swelling of pretty well the whole female flower, which is on a stalk or pedicel. The structure next to it contained a male flower – there are usually several – reduced to consisting of a stamen on a stalk. The fruit capsule splits open explosively to scatter the seeds. Thus what looks like a flower is in fact several, male and female, grouped inside two blades which seem to be half leaf, half petal, and which are called the  cyathophylls – the whole structure being called not a flower but a cyathium.

Mercurialis annua – male plant

Now the relative, Mercurialis annua (annual mercury), also a member of the Euphorbiaceae and  a common weed throughout Europe. Here the male and female flowers occur on separate plants – this plant, like the others near it, was a male, as you can see if you look closely at the picture – there are tiny stamens poking out of the simple flowers. I haven’t found a female plant to photograph yet, and I think they prefer different habitats – I’ll keep you posted.

I’m not the only one fascinated by spurges – ‘Happiness is a state of Euphorbia’ proclaims one person’s website dedicated to these plants. And all the basics you need to know are very well explained, with diagrams, on the site of the international study group for this family of plants, the EuphORBia Portal (so named to indicate the comprehensive and planetary scope of the project) – click on the link here.

If I want to mark how odd these plants are, I can think of nothing better than to show some clips of the musician Sun Ra. Here he is in the film Space is the place (1974) trying, hilariously, to explain himself  to members of  a black youth club. Maybe spurges came from his planet.

And on the day of news that the founder of the Montreux jazz festival, Claude Nobs, has died, here is Sun Ra and his Arkestra performing at Montreux:

Coming up next: more stuff you didn’t want to know (till now) about spurges.

 

 

New gear resolution

I’d like to start by wishing all of you who have found your way to this blog:

Happy New Year!

Blwyddyn Newydd Dda!

Bonne Année!

Bona annada plan granada!

Many thanks to everyone for your interest and comments since I started last year, and welcome to anyone visiting here for the first time. It’s New Year’s Day, you haven’t got time to read, and nor have I to write much. This is a short post to share some images of flowers taken over the last few days, to show there is life out there in the middle of winter – helped by a recent mild spell with some sunny days when the temperature reached 16 degrees. And of course I’m also showing off my new camera and lens – the title isn’t a typo.

Iris unguicularis

The Algerian Iris (I. unguicularis) – originally from North Africa but grown widely in gardens, and the first Iris to flower. This was in some waste ground next to an electricity substation – it was probably planted there, and has spread and settled. It’s a very low-growing species, and my flower book says the ovary is at or below ground level – amazing, I’ll have to look closer next time.

Geranium rotundifolium

I think this is the round-leafed crane’s bill – all the little geraniums look very similar to me.  If I keep at this, I hope I’ll get better at telling them apart.

Euphorbia

Yes, but which Euphorbia? I’m planning a longer post soon on the great variety of species of spurge round here, because I find them bizarrely fascinating. And I love their shades of green and yellow.  The little yellow star-shapes are nectar glands, and the buds are separate male flowers – the female flower usually grows in the middle of the glands. Found by the side of the road – Chaiselongue said to me, ‘You know, all the people who pass in cars are looking at you strangely – they think there’s only one thing you can be doing crouched down in a ditch.’

Viola alba subsp. dehnadii

The first violet I’ve seen, on the path just by our garden – had to lie flat on the ground to take this. The Latin name is a bit confusing, but there is a white subspecies too (scotophylla) , found in the Balkans.

Resolutions: To work on a comparison of the various spurges, as I’ve said. And other topics I’ve got in mind include something about the social life of plants (yes, really), more on the beach bums of the plant world who survive on the sand dunes, the wonderful plants of the garrigue, a botanic garden mystery ( a Kewdunnit) – and much more. Hope to see you again many more times in 2013.

And there will be more Brazilian music too. Here’s the genius Baden Powell showing how to play with a lit cigarette: