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Field notes from Mexico 6 — a botanist in the museum

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On my last day in Mexico, my hosts kindly took me to see the National Museum of Anthropology in Mexico City. First of all — wow. It’s absolutely spectacular, and if you have even the slightest interest in human history, culture and archaeology then you should go. Much like the British Museum* in London, you simply can’t take in the whole place in a single day. In fact, you would struggle to do so in a week.

In a single afternoon I was only really able to take in two archaeological sections: the Mexica empire, and the civilisations of the Pacific coast. The former were characterised by a militaristic state, the latter by their complex cultures and fine crafts. In fact, I was even more focussed, as I was specifically looking for evidence of botanically-inspired features among the artefacts, and I found plenty.

Many of them, interestingly, were related to cacti. This surprised me. Although Central America is the cradle of cactus diversity, and they are the most distinctive feature of Mexican dry vegetation, they are also relatively unimportant as crops and a minor component of most systems. Evidently they were considered worthy of carving into stone though.

In the section on the Mexica, rulers of the Aztec Empire, there is an altar with an Opuntia (prickly pear) clearly depicted on the rear face. This distinctive cactus provides a useful resource: its pads, once cleaned of the spiny glochids**, are cooked as a vegetable, known today as nopales, a word which derives directly from the Nahuatl as spoken by the Aztecs. Likewise the fruit, tuna, is still harvested and eaten widely in Mexico. The name Opuntia itself, however, is from the reference by Theophrastus to a plant in the classical Greek city of Opus which could grow from a leaf that was stuck in the ground. He wasn’t talking about a cactus though, because although they are now invasive in some parts of the Mediterranean, they definitely hadn’t arrived there in 300 B.C.

A stone altar with Opuntia carved into the rear.
Reconstructed burial with corpse placed on a pile of Opuntia pads.

 

Opuntia isn’t solely used for food though; one of its more surprising appearances was in a reconstruction of a burial chamber from La Cueva de la Candelaria, on the border between the modern states of Hidalgo and Durango, which was occupied around 1100–1300 AD. The bodies each rest upon a layer of Opuntia pads. It hardly seems like comfort — no-one would do that if they were alive — perhaps these were provisions for the journey beyond?

Other cacti have more entertaining functions, such as peyote (Lophophora williamsii), a favourite hallucinogen for ritual and recreational use. It appears as a design on a large pot, and also in my favourite piece in the museum, a ring of revellers surrounding a shaman who is clearly holding a cactus in his hand. Both are from the Tumbas de Tiro tradition of West Mexico (200–600 AD).

Peyote on a pot.
The shaman in the centre is holding a peyote.

RIMG2623To finish off the cacti, how about this metre-tall carved columnar cactus, probably from the genus Cereus? I definitely coveted this for a corner of my living room. It’s thought to be a boundary marker between two territories, and has the face of a legendary Mexica leader carved into its base. What interests me is that this kind of cactus isn’t present in that area, at least not in the modern world. Was it chosen because it was a feature of the landscape back then, or alternatively because it would stand out as unusual?

Other plants have important cultural associations. I’ve mentioned Agave before on this trip, particularly with reference to the manufacture of the alcoholic beverage pulque. I learnt much more in the museum though. Pulque had its own god, Ome Tochtli, which translates as ‘Two Rabbit’. Adults were only permitted one drink of pulque in any sitting (size not specified), and drunkenness was heavily frowned upon, lest one lose control and fall under the violent spell of Cenzon Totochtin, or ‘Four Hundred Rabbits’ (which, wonderfully, is the name of a popular brand of mezcal). So remember kids, two rabbits good, four hundred rabbits bad.

RIMG2635Another impressive piece of Mexica sculpture was this calabaza (Cucurbita moschata), a relative of the modern pumpkin. This magnificent piece was the size of… well, a ripe pumpkin. Alongside maize, which appeared in countless exhibits, beans and chilli, this was one of the staple foods of the peoples of central Mexico.

Not all the exhibits were carved in stone. One of the most important documents held by the museum is the Botorini Codex, a long pictographic account painted on fig bark by an Aztec artist around 1530–1541, so not long after the Spanish arrived. It tells the legend of how the Aztec arrived in the Valley of Mexico after leaving their original home of Aztlan. They decided to settle there due to the abundance of resources, but their first action was, of course, to cut down the trees. This is a useful reminder that tropical deforestation is by no means a new phenomenon, even if its intensity has increased in the modern world. One puzzling mystery though: why does the tree have arms?

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A section from the Botorini Codex illustrating the clearance of forests in the Valley of Mexico following the arrival of the ancestors of the Aztec.

Finally, I’ll finish with another Mexica carving. On first inspection it looks like a bird sitting in a stylised flowering tree. But look more closely and you’ll see that the bird is eating some kind of caterpillar. In other words, it’s an archaeological representation of a tritrophic interaction! Perhaps they would have been unsurprised by findings of ecologists in Panama 500 years later that birds protect trees from herbivory.

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Bird eats caterpillar eats tree. Tritrophic interactions in archaeology!

* Which is an order of magnitude larger again, thanks largely to the pillaging of cultures around the world in the name of empire, such as in the notorious case of the Elgin Marbles.

** Bristly patches of spines on some cacti, which often have barbs and detach when touched. I recommend a bar of soap to remove them. Then throw away the bar of soap before anyone else uses it by accident.

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Field notes from Mexico 5 – ghost plants

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Monotropa uniflora in the understorey of an Abies religiosa forest, El Chico National Park, Hidalgo, Mexico. Thanks to Sarah Pierce for the ID.

On numerous occasions on our trip through the coniferous forests of Mexico on the #PinaceaeGo project, we’ve encountered a ghostly pale plant on the forest floor. Depending on where in the world you’re from, it might look very familiar; or totally unlike anything you’ve ever seen before. That in itself is part of the mystery surrounding this plant.

Monotropa uniflora is variously known as the ghost plant, corpse plant, or Indian Pipe. As its appearance suggests, it is parasitic, and does not contain any chlorophyll of its own for photosynthesis. Unlike most parasitic plants, however, it doesn’t obtain its energy from other plants. Instead, it is an unusual example of a mycoheterotroph* — it steals sugars from mycorrhizal fungi in the soil which are themselves symbiotic partners of trees. In other words, the trees choose to associate with the fungi, providing them with sugars in return for soil nutrients. Monotropa hijacks this arrangement and takes from the mycorrhizae while offering nothing in return.

This indirect theft is what allows it to survive even in dense, dark forests, and to be associated with a range of forest types. While most parasitic plants target particular plant species, M. uniflora is highly specialised on a few species of mycorrhizal fungi from the Russulaceae. All these features set mycoheterotrophs apart from more common parasitic plants such as dodder (Cuscuta spp.) or broomrapes (from my favourite plant family, the Orobanchaceae**), which are direct parasites on other plants.

Confusion over the taxonomy of Monotropa has been long-standing. Prior to Linnaeus, a related species Monotropa hipopitys was actually included in the genus Orobanche. Early botanists must have thought that parasitism ranked as a higher criterion for organising plants than flower traits. For a while it had its own family, the Monotropaceae, but it is now incorporated into the Ericaceae, along with heathers and Rhododendron, which superficially look nothing like it.

Another of its bizarre features is what biogeographers refer to as a disjunct distribution. It occurs in all sorts of places worldwide, in Russia, North and South America, but with large gaps between them. Genetic evidence suggests that these are distinctive, but not enough to call them different species. How did they get to such widespread locations? Was it through their dust-like seeds, or linkages in previous climates, or human transportation? Even where it is found, it’s never very common, and appears only in certain seasons.

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Global distribution of Monotropoideae (including Monotropa uniflora) from Kathleen Kron’s Ericaceae site.

It’s not often that one can come across the same distinctive species in so many places around the world. How did a species of heather come to evolve into a fungal parasite, to develop such a strange form, and to spread itself quite so far? Wherever you find it, it’s always going to be special and mysterious.

* Here’s a pretty old review of this group of plants from 1994. If another has been published since then I’m unaware of it, and suggests that there might be scope for an update.

** One day I hope to retire to a herbarium and prepare a full review of the Orobanchaceae, so long as no-one else gets there first. I collect them on sight, wherever I am in the world. This is probably a pipe-dream. I’m never going to retire…

Field notes from Mexico 4 – tree farmers

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Pico de Orizaba looms large over the landscape of Veracruz State, Mexico. From this vantage  point we’re still 3000 m from the summit.

There are two main crops grown on the northern slopes of Pico de Orizaba, a dormant volcano and the highest mountain in Mexico*. Unsurprisingly, one is maize, the standard subsistence crop in this region. The other is the pine tree Pinus patula.

A maize field on the valley floor
A developing plantation of Pinus patula. Here, close to the village, they also graze sheep beneath them.

We’ve spent two days this week getting to know the northern face of Pico de Orizaba, which is the side where the majority of coniferous species are found. As in so many parts of the world, our explorations are complicated because anywhere that’s accessible has been transformed by humans, which means that even if we can spot intact forests through the telescope, reaching them would be nigh-on impossible without a guide, climbing gear and a lot more time.

The first day was spent on the ridge tops, trying to get a view down into some of the valleys and find a promising route. This was a race against time as the cloud falls rapidly over the course of the day, shrouding everything in thick fog. Eventually we spotted some tall old-growth stands and reached a friendly village where they showed us the trail to reach them. We scouted a short way up the ridge but heavy rain put paid to any further adventures.

The next morning we set out to climb the narrow gorge which led to the forests we wanted to reach. On several occasions we hit waterfalls and had to turn back to climb around them. It also poured with rain for a large part of the day. Our determination was rewarded, however, when we finally emerged into some grand, full-stature forests of Pinus patula, mixed with some P. ayacahuite and Abies religiosa. It was a breathtaking sight and made the long climb worthwhile.

Hiker: “What a gorgeous waterfall!”. Forest ecologist: “How am I supposed to get up this gorge now?”
Bedraggled, but you can see the tall pines just upstream in the valley behind me.

We weren’t the first to reach them though. All the way, our trail had been pock-marked by the hooves of donkeys. It soon became apparent that what we had reached was not an isolated remnant of forest but the current front line of an ongoing, small-scale logging operation.

The dominant cottage industry in this region is the manufacture of low-grade crates and pallets, the kind that are used to transport fruit and vegetables. Many households are surrounded by mounds of sawdust; often someone (usually a woman) is sat outside knocking together an endless series of crates. The improvised sawmill providing the planks is around the back. Their dominant raw material is Pinus patula.

Even in this remote location, the chainsaws get here first.
The forest remains but the giants are being lost.
The end product: stacks of crates.
Charcoal production is another cause of forest loss.

Which brings me back to my comment at the start of the post about farming Pinus patula. Government grants have provided landowners in this area with thousands of seedlings of Pinus patula, which are now being planted all through the valleys. Men can be found peppered across the slopes, clearing the brash and shrubs away in order to plant yet more. The scheme has obviously been running for several decades because, in a few places, the trees are now reaching harvestable sizes.

I will confess to having mixed feelings about this. There is no doubt that the main driver of loss of these magnificent ancient forests has been the manufacture of cheap pine products. On the other hand they are, in some sense, being replaced, which means that the activity could in the longer-term become sustainable. Farmers are at least planting a native tree species, and one which clearly belongs in these valleys. It will act to reduce erosion, prevent flooding, and although not as good as old-growth stands, plantations will still provide habitat for many of the species that formerly inhabited the forests. The waste products — bark and other off-cuts — can be used as fuelwood to reduce their dependence on other sources such as charcoal. Finally, making crates provides a stable income for communities who have lived on and farmed these slopes for generations.

This landscape is so rugged, the topography so steep, that there will always remain some places where the native vegetation persists, out of reach of both donkey and chainsaw. These may only be small fragments but they are crucial in providing continuity, seed sources and safe redoubts from the encroachment of civilisation. I may never reach them or survey them, but I am glad to see them from my telescope, and know that they still exist.

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This beautiful forest is under threat. But somewhere in these mountains others like it will remain, simply by virtue of their inaccessibility.

UPDATE: in between writing and posting this piece, the aftermath of Storm Earl led to multiple deaths in the area around Coscomatepec, where we were staying, due to flooding and landslides. It’s worth remembering that behind the headline figure of fatalities is always a larger story of survivors who have lost houses, crops, livestock; many villages will have been cut off. Mexico is a beautiful country but one with great disparities in wealth, and in this tragedy the heaviest burden will fall on those least able to cope.

* Its total height is 5,636 m, but most striking is its prominence, rising 4,922 m above the surrounding landscape. It really does stick out.

Field notes from Mexico 3 — Pulque Party

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Caution — drunkards. My favourite warning sign on the roads*. The source of their booze, the maguey plant, is on the left. Photo: Libertad Sanchez-Presa.

Once you leave the main roads and cities, a large amount of Mexican culture revolves around the Agave. Its most internationally renowned member is the blue agave, Agave tequilana, whose sugary heart is used to make tequila. A less well-known drink is mezcal, which can be made from a range of Agave species, and by small producers. This allows for a wide variety of styles and flavours, making it a more diverse and interesting drink than mass-market tequila.

In the region where we’ve been working, however, the dominant species is Agave americana, known as maguey. The plants are everywhere, either as dedicated plantations, scattered among crops, or surrounding houses and smallholdings. They’re not just a weed though; they are carefully tended and visited regularly to harvest the sugary sap from their core, known as aguamiel (honey water).

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The heart of the maguey plant contains a pool of sugary sap (aguamiel). In this case it is protected from evaporation and contamination by a plug of igneous rock.

During our hunt for the lost firs, which was a great adventure, we ended up walking through a number of farms in the foothills. In one we met a local woman collecting her aguamiel, who showed us how it was done. The process is pretty simple: a coke bottle with a hole in the bottom and a tube attached is used to suck the liquid straight out of the core, then drained into a bucket. She then scrapes out any scum or accretions on the bottom of the core, which ensures that the plant continues to secrete more sap through what is effectively an open wound. Most of her teeth were missing, which can probably be attributed to a lifetime of doing this.

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A local farmer near Metapec sucks the sap from the heart of a maguey plant using an improvised bottle with a tube attached.

She offered me some and, being generally willing to try everything, I naturally obliged. It’s sweet with a distinctive flavour, in this case enhanced by a number of dead flies which added an interesting mouth feel.

In some places you can buy the aguamiel pure, though one imagines they filter it first. Its most important value, however, is to be fermented into the mildly alcoholic** beverage pulque. As you drive through rural areas there are occasional improvised signs next to shacks declaring its availability. Pulque is sold by the litre***, dispensed into whatever container you have to hand. We’ve been using old plastic water bottles, though this makes them impossible to ever use for water again because the pulque leaves a lasting unpleasant odour in the bottle.

It’s best drunk fresh because it continues to ferment in the bottle, which shouldn’t be closed too tightly as the build-up of gas can cause it to explode, especially if you’re bumping along dirt roads as we tend to be. Left for too long it becomes viscous and unpleasant.

The drink is the favoured end-of-day beverage for labourers, serving the role that beer plays elsewhere in the world. It’s slightly sweet, frothy and refreshing. We’ve tried a number of pulque shacks and experienced the full range of quality. Some was delicious and moreish, another so bad that one sip had us spitting it out and feeling queasy for the rest of the day. We’ve been going for pulque natural, the pure version, although in many places you can buy it flavoured with fruit juices.

Pulque is also used to make the dish barbacoa, a speciality of the State of Higalgo, which is meat (usually pork) soaked in pulque, wrapped in maguey leaves and baked. The result is something like pulled pork; tender and juicy with a characteristic flavour. It can then be wrapped in a taco with the usual accompanying relishes.

Is there a potential mass market for pulque? Personally I doubt it. Achieving greater quality control and consistency would not be impossible, but the difficulties of transporting it and keeping it fresh mean it’s unlikely to supplant beer. In the villages and rural parts of the country, however, it remains an important part of daily life. It’s also a great way to finish a long, tiring day of fieldwork in the forest.

* Not, I should add, an official Mexican highways sign. Someone had stuck their own sign on top of the existing one. Drunkards of Mexico, we salute you.

** I sank a litre of it by myself a few nights ago. It didn’t get me anywhere even close to drunk but it did give me a vicious hangover. I won’t be trying that again.

*** We’ve paid 10–12 pesos per litre, which is around 50 pence.

Field notes from Mexico 2 — Lost Valley of the Firs

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UPDATE: this post is followed by an embarrassing correction. I’m leaving the original in place, unchanged, because I don’t want to hide the fact that scientists sometimes (often) make mistakes, and are as prone to over-enthusiasm and optimism as anyone else. So please read on, and don’t judge us too harshly for admitting our errors. 

We have rediscovered Abies hidalgensis! This is an amazing find, and a real boost to the PinaceaeGo project. It took two solid days of hunting on inaccessible mountain slopes. To understand why this species is so important, we need to start at the beginning, with some fine detective work in the herbarium by awesome PhD student Libertad Sanchez-Presa.

Abies hidalgensis was first described in 1995 by a Hungarian botanist following a collecting expedition the previous year*. Unlike all the other ‘new’ species described in that paper, it survived subsequent critical review by Aljos Farjon, the world expert on conifers and a notorious lumper**. Libertad uncovered the type specimen in the National Herbarium of Mexico at UNAM in Mexico City. Everything about this species sounded dubious. The description of the collection locality didn’t match the co-ordinates, which were 30 km away. It was supposedly found at 2300 m altitude, whereas we haven’t seen Abies below 3000 m anywhere else in the country. Most of all, this is an arid area, and firs are usually found in dense, damp, dark forests. Nothing we saw on Google Earth suggested that such a location existed. She decided that this mysterious species was worth tracking down.

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This is the duplicate specimen of Abies hidalgensis held in the Kew herbarium (obtained via HerbWeb). That label is all the information we had to go on.

Our journey began with a drive up from Puebla to Tulancingo in the state of Hidalgo, where we spent the night. An early start took us to the vicinity of Metapec, a small village to the south of the mountain range where the species was described. From there we took dirt roads as far as we could towards the location described on the sheet, though the details couldn’t be matched to the actual landscape.

For one day we hacked up and down gulleys and over ridges, sweating in the heat. We saw some amazing stuff: a huge tarantula hawk wasp killing a large spider then dragging it away; a wild Mammillaria cactus with edible fruits, which we ate; some oak ‘apples’ (really galls formed by insects) large enough to deserve the name; and an array of spectacular mushrooms. Some of our findings will be the subject of a future post.

Tarantula hawk wasp dragging its dead prey
Mammillaria sp. with edible fruits
Oak galls
I should have provided a scale here, because these mushrooms were huge.

What we didn’t see were any fir trees. More concerning was that we didn’t even see any habitat where Abies was likely to be found. There was plenty of dry pine forest and scrubland, but even scanning the slopes and plunging into the valleys revealed no firs or even evidence that they might once have been there. By late afternoon we were tired and disheartened. Had the species disappeared? Did the collector get their field notes mixed up?  Was it an elaborate hoax? All sorts of explanations ran through our minds.

A dry valley. No Abies here.
Right altitude, wrong vegetation. Libertad and Sarah keep their spirits up regardless.
A patch of lichen-draped cloud forest. Nope, no Abies here either.

Typing the co-ordinates into my GPS gave a location 30 km away in the state of Veracruz. This was a long way from the site description, but it was at least up in higher mountains where Abies might more plausibly be found. There was nothing for it; we had to look. The actual driving distance was more like 50 km, ending up on dirt tracks in remote villages. All we found were large plantations of exotic trees that the locals referred to as ‘Chinese pine’ (perhaps Pinus koraiensis?). If the Abies had been there once then there was no sign of it now, nor of any native vegetation. We drove back, 100 km of wasted effort.

All the way back to Metapec we were haunted by visions of Abies in the forests around us. More than once we screeched to a halt, convinced that one or other of us had spotted something, only to discover it was just another Cupressus lusitanica. 

As we drove past the ridges we had been exploring earlier in the day, it was late evening, and the setting sun was illuminating the slopes. Sarah spotted some conical trees unlike anything we had seen that day. We pulled out the telescope and peered through the dusty haze. There was definitely something up there, tucked away in an inaccessible valley… but we had become rather jaded by our earlier experiences and were no longer willing to trust our eyes. Besides, it was 10 km away, and there was no hope of making it up that evening.

The next day we had plans to inspect another site, but made the difficult decision to try again, one last time. If it was there then it would be remarkable; if not then we were all ready to remove it from our biogeographical analyses as an aberration. We started out from a different point, navigating through the slopes towards the valley Sarah had identified from the road.

Emerging onto a ridge crest, it was Sarah who again noticed something unusual. On the next ridge north of us, atop an escarpment a few hundred metres away, a small tree was poking up with a distinctive conical form. It was only around two metres tall and, squinting through the telescope, it looked like it just might be an Abies. Reaching it would be extremely dangerous though. We pressed on.

We climbed further up until we reached a high ridge at 2600 m close to our target location. It was lunchtime and we were tired and hungry. We dropped bags and looked around the typical oak-alder forest. Libertad pointed towards something growing in the understorey. Could it be?

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Sarah celebrates finding the first Abies seedling. It’s just to the right of her.

She ran over and confirmed — we had an Abies! In fact, they were all around us. But at this altitude, in this vegetation, was extremely peculiar. It wasn’t anything like the normal conditions for Abies, nor in fact much like the site description from the herbarium records. None of this made much sense. As we descended down the opposite, north-facing side of the ridge, they were everywhere. The tallest individuals exceeded 20 m in height and 50 cm in diameter, with a range of sizes and plentiful seedlings. But they were growing in dry, open conditions, on a ridge with cacti nearby; how was this possible?

We only had a few hours before we needed to return home. In that time we managed to collect herbarium specimens, tissue samples in alcohol for genetic analyses, trait data for our own work and core two large stems***.  The steepness of the slopes, peppered with escarpments, made it impossible to descend far into the valley below, but we could see more Abies down there and on the opposite slope. Talking to a local farmer later that evening it sounds as though another route into the valley exists, which we may explore next time. We left as late as was safe, exhilarated and exhausted, and also a little frustrated at not being able to stay longer and collect more data.

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Two large, healthy specimens of Abies hidalgensis, right on an exposed ridge top. This is not where we would have expected to find them.

What now? We have the trait data we were looking for, and can confirm not only the presence of this species but also its exact location. Our samples will be sent to local herbariums and experts; hopefully the tissue samples will allow a systematist to determine the true place of this species on a phylogeny and identify its nearest relatives. We are also a little puzzled by the cones, which don’t look much like those on the existing herbarium specimens.

That’s not where this story should end though. The species is listed as vulnerable on the IUCN Red List, which is reasonable given that the range of this population can be no more than two square kilometres. One hot summer and a severe forest fire could severely deplete its numbers, a disaster which becomes increasingly likely in a warming climate. Having found the species again, we now bear some responsibility to do something about it.

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So far as we know, these two valleys encompass the global range of Abies hidalgensis. Rumour has it that there are some more close to the village of Agua Blanca to the north, but we were unable to confirm this.

What this action should be is something we will need to discuss. Perhaps we could undertake a comprehensive mapping exercise and population estimate; press for the designation of a protected area; collect seeds or propagate live material for ex situ conservation; set up a mapped forest dynamics plot… all could be the subject of future work.

Personally, I think the most important outcome should be a local education campaign. We spoke to many locals and farmers over the course of the two days, yet only one knew about the species. These are people for whom this forest is on their doorstep, who use it to hunt or collect firewood and mushrooms. Realising that their forest contains a tree of global importance and interest should be a matter of great pride, and will be the key to ensuring that it remains well protected.

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Libertad’s plant press contains that most precious of cargoes: herbarium specimens of Abies hidalgensis, the first to be collected for over 20 years, linked to a much greater amount of contextual information and data on the individual trees.

* Their visit is described briefly in this paper. They didn’t manage to see a great deal on their two trips up the mountain.

** Taxonomists are often broadly stereotyped as ‘splitters’ or ‘lumpers’. Splitters have a propensity to declare new species on the basis of fine differences among populations, sometimes as much through wishful thinking as meaningful variation. Lumpers review these designations and collapse them into single species. Splitters don’t like lumpers because they take ‘their’ species away. This tension has been present throughout the history of taxonomy.

*** Coring carries a small risk to the tree, and therefore should only be performed with a good reason and where you can be confident that there are plenty of individuals. From these cores we can determine the growth rates of the trees and look for any indication of climate dependence or changes over time.

IMPORTANT UPDATE (18 August 2016)

Well, as the new header on this post might have given away, we didn’t actually find Abies hidalgensis. We had grown increasingly suspicious of our collection over the days that followed, and on depositing the specimens in the herbarium at Monterrey, our fears were confirmed. We had actually collected Pseudotsuga menziesii. 

How did three experienced plant ecologists come to make such a big mistake? There are a few mitigating factors. Psuedotsuga  wasn’t previously recorded in this area, so we weren’t expecting to see it. We were tired, clutching at straws, and perhaps too ready to leap at anything that looked like an Abies. Finally, they aren’t that easy to tell apart. I should be embarrassed because I know Pseudotsuga menziesii well from North America (its common name is Douglas fir), but the local Mexican type actually looks very different, and some botanists have tried to designate it as a different species. I won’t comment on this other than to say that the accepted approach is to consider it as a single species with sub-specific variants and a high degree of morphological variation.

Where does this leave Abies hidalgensis? We still don’t know. The original collection records for the type specimens are contradictory and bear little resemblance to the landscape of the area. We tried everywhere that sounded roughly right, or that looked like it might be Abies habitat, and a lot of places that weren’t, just in case. We did everything we could to find this species in the time available and failed. Is it actually there at all? Was it ever? We are back to having some serious doubts about the very existence of this species.

As for our error, it’s an excellent demonstration of why scientists publish in journals rather than online blogs. When we submit a paper, as we would eventually have done, our findings go through many layers of careful scrutiny. It takes a long time, and many ideas fall by the wayside in the process. It’s easy to dash off a small blog post in the evening with a beer and claim quick credit, but were these to be treated as findings equivalent to published articles, it would carry the risk of mistakes ending up in the body of scientific knowledge. So you should never automatically trust a blog post, press release or similar non-standard means of transmitting a scientific finding. It may get more attention than a paper published years later, but it carries a high risk of being wrong, as we were.

Still, we had fun :o)

Field notes from Mexico 1 — Pinaceae Go!

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For the next five weeks I’m based in Puebla, Mexico. It’s a beautiful location: an historic city (the centre is a World Heritage Site) surrounded by spectacular archaeological sites and with a horizon dominated by snow-capped volcanoes*. There’s not much time for tourism though; we have a packed itinerary.

The first three weeks will be taken up with a single mission: collecting trait data from as many Mexican coniferous species as we can find. Hence the nickname of the trip, Pinaceae Go!** Because finding real trees is way more fun than hunting virtual creatures on your mobile phone. We also stand a chance of spotting the legendary volcano rabbit, which sounds as though it should be a Pokémon.

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The Pinaceae Go team — myself, ecologist Dr Sarah Pierce and PhD student Libertad Sanchez-Presa. And, in the background, the real object of interest: Abies religiosa on La Malinche volcano.

Why Mexico? The reason is that the country is the centre of global diversity of conifers. Of the 120 recognised species of Pinus worldwide,  49 occur in Mexico***. The country also holds 7 of the 18 species of Cupressus, 8 of 48 species of Abies, one each of the four species of Pseudotsuga and Calocedrus, 3 of the 38 species of Picea and 20 of the 68 species of Juniperus. That’s quite a haul. Of those seven important genera, Mexico alone contains 30% of  global species richness.

So what? There are other centres of tree diversity all around the world. Why is this one in Mexico special?

The reason this particular hotspot baffles me is that current opinion in forest ecology suggests that conifers can’t reach high levels of species richness. This is because classical theory argues that conifers don’t have the flexibility of traits and growth forms available to broad-leaved trees. Conifers all have roughly similar branching patterns, leaves**** and wood. It’s relatively easy to understand how multiple broad-leaved tree species can coexist by having distinctive traits to reduce the degree of competition among them. Such a wide range of variation simply doesn’t exist in conifers.

This account may appear compelling to a temperate ecologist, who will know of the vast boreal forests containing only a couple of coniferous tree species. It falls apart when faced with the montane forests of Mexico.

To illustrate the scale of the problem, our very first sampling location provided a perfect example. We drove along a dirt track up the side of the famous active volcano Popocatépetl, stopping at around 3000 m altitude to have a look around the forests. It didn’t take long to start building our database. Within 100 m of the road we were able to sample five species of Pinus, one Abies and a Cupressus. We weren’t even trying very hard; this was an introductory walk to test our methods rather than a systematic sample.

Libertad takes measurements of cones and leaves.
Our pole saw didn’t arrive on time so Sarah improvises with her ‘stick of power’. She insists on calling it that.

Ultimately the questions Libertad would like to answer include:

  • At what spatial scales does the coexistence of so many species of conifer occur? Are they growing side-by-side, or specialising on distinct types of habitat?
  • Do the traits of conifers determine which species are found in coexistence? Do these traits change among locations or depending on the presence of other competing species?
  •  What drives patterns of species and trait diversity in conifers on biogeographical scales?

We’re only at the beginning of this project; Libertad is still in the first year of her PhD and this is the first fieldwork we’ve done. A large amount of trait data is in the literature already, along with the Mexican national forest survey. We’ve been processing all this information over the last few months. Our aim for this trip is to supplement this with missing species and new locations. Gotta catch them all…

* Your view of snow-capped volcanoes may depend upon air quality.

** Conifers include the pines (Pinaceae), hence the trip nickname. Conifer Go would have been more accurate, but wouldn’t have sounded as good.

*** Let’s not get into arguments over taxonomy. We’re following the opinion of Aljos Farjon, generally acknowledged as the world expert on conifer systematics, and bane of splitters.

*** Yes, they are still leaves, even if they are colloquially referred to as needles.

Field notes from Uganda 8: Farewell, potatoes

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It’s the end of the field course here in Kibale and I’m now looking forward to getting home. The day my plane lands there’s a wedding to attend, but even before that there are many things I’ve missed — my wife, hot running water, reliable electricity, my record collection, and the ability to walk in the forest without fear of being trampled by elephants.

On the very last night here I went out with a small group to look for bush babies. We were rapidly successful, scanning trees with our torches and looking for the orange reflections of their large eyes amongst the foliage. I was walking slightly ahead, looking for the next one, when from the vegetation at the side of the road, moving as silently as an iceberg, a large bull elephant emerged right in front of us. What are the chances. It made it clear that we were not welcome, but luckily wasn’t interested in causing us any further trouble.

The elephants will not be missed. There are, however, a number of things that I will remember fondly. In no particular order:

1. The potatoes. I’m not joking. The potatoes here in Uganda are the best I’ve tasted in my entire life, especially when roasted. I could eat them continuously. I’ve never had potatoes like them before and all others will pale in comparison. The only other foodstuff worthy of note are the doughnuts of death, which occasionally appear at afternoon tea — small blobs of hard, salty deep-fried dough. They’re basically vegetarian pork scratchings and they’re incredible, even though each one palpably reduces your life expectancy.

2. The students. Normally at the end of a field course I watch the tearful parting of the participants with absolute equanimity. It’s not that I’m glad to get rid of them so much as relieved at the lifting of responsibility and the peculiar social tension that results from the teacher-student relationship. On a TBA course, however, it’s completely different. All the students are mature post-graduates, all highly talented and motivated. It also helps that we’re not assessing them, which allows us to completely separate the important roles of teaching and support from any academic judgement. This dissolves one of the major social barriers, and not coincidentally, they learn a lot more as a result.

3. Primates. To quote Liza Comita, a fellow forest ecologist, if you’re going to do dull and repetitive fieldwork, do it somewhere with monkeys. I’ve never been anywhere with such a fantastic abundance and diversity.

4. This view in the morning:

frontview

One could easily get used to opening a front door to this view.

Some things, however, I won’t miss at all.

1. Ironing underpants and socks. This isn’t for aesthetic reasons, but to kill the eggs of the mango fly, which are often laid on wet clothes when they’re hung out to dry. On contact with skin the eggs hatch and the larvae burrow under the skin causing painful, infected swellings. One of the other teachers has pulled almost 40 larvae out following an unwise excursion to the swamp where they swarm in abundance. This has been enough of a warning to make everyone a little paranoid.

2. Finding an internet connection. In the Dark Ages, monks travelled the world looking for the exact location where the firmament was thinnest and their prayers would ascend most readily to heaven. High, desolate places were particularly favoured for establishment of holy sites. The same principle applies to obtaining a mobile signal in Uganda. I am sending this while sat on a pile of rocks on the hill above the field station. Returning to a place with reliable wireless will be a delight.

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On this occasion, the internet beam fell around the septic tank

3. Elephant terror. Once you’ve had a bad experience with the elephants, every noise in the forest becomes a potential elephant. Branches swaying in the wind, an animal running away in the undergrowth, a hornbill squaking as it lands clumsily in the canopy. All these make me jump and scan for the nearest escape route. In most forests I’m confident that, as a human being, I’m pretty much the most dangerous animal around. Everything else tends to run away. Here I’m definitely not. It’s a new experience for me to be scared in the forest and it’s not one I’ve enjoyed.

4. This view in the morning:

baboons

The baboons hold their morning conference to plot the day’s mayhem.

Actually, the baboons aren’t too much of an issue, so long as you ensure that your doors and windows are locked whenever you’re not around. They’re certainly not aggressive, other than to each other. In a place with limited electricity and internet, an no TV, they provide a permanent soap opera on your doorstep. The researchers who study them have almost come to love them. I doubt I’ll ever get that far but they at least provide good entertainment. It still baffles me though that a standard greeting among male baboons is for one to grab the other’s testicles. It’s one way to get their attention I suppose.

Field notes from Uganda 7: Journey to the Mountains of the Moon

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The three teachers on our Tropical Biology Association field course here in Kibale abandoned the station for a day trip to the Rwenzori mountains, around two hours drive away (if nothing goes wrong, which it did). These fabled peaks are known as the Mountains of the Moon and comprise the tallest mountain range in Africa*. The Rwenzori Mountains National Park runs along the border with DR Congo where it merges with Virunga NP on the other side. Both are UNESCO World Heritage Sites.

We began at the main park gate at around 1700 m and were led by our guide through several kilometres of valley floor which had been cultivated prior to the park’s gazetting. This remained in a rather sorry state, with little evidence of regeneration. I wondered why this might be the case, and whether this was a site where assisted regeneration through tree planting would be justified. Regardless of the stature of the vegetation, however, it makes good habitat for several of the endemic chameleon species, as well as an easier habitat for the bird watchers**.

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One of the local endemic chameleon species — not easy to spot. Photo credit: Kate Lessells.

After a while the gradient steepened considerably as we ascended a knife-point ridge which afforded spectacular views on each side, as well as supporting a forest vegetation quite unlike the steep slopes. I say steep; if you fell then you wouldn’t bounce many times before reaching the white water at the bottom. It’s a wonder any vegetation clings to them at all, though in fact they’re covered by a mosaic of wooded patches and tangles of vines and shrubs.

After a 1000 m climb we reached the top of the ridge, panting and with burning muscles in our legs. We emerged into some delightful cloud forest. Trees were shrouded in the characteristic straggly Usnea lichens, and branches bore dense carpets of aerial-rooted epiphytes. Combined with the fresh breeze blowing across the mountains it was a narrow strip of paradise.

epiphytes

A carpet of epiphytes cover this branch hanging out over a steep ridge slope.

Above this, at around 3000 m, lay what I was really interested in — bamboo forest. I’ve heard about it but never had the opportunity to see it for myself. It was majestic; giant bamboos tower above you to a height of around six metres, and scattered amongst them are ancient Podocarpus trees which frequently exceed a metre in diameter.

Almost all the trees were large, with relatively few smaller stems. This made me wonder about the processes regulating these forests. I presume that episodic dieback of the bamboo (which happens after they flower en masse) opens up occasional opportunities for tree regeneration, perhaps only a few times a century. Those lucky recruits which manage to establish can then survive until the bamboo crowds around them again. This is my guess; once I get back to a reliable internet connection there will be plenty of reading to do.

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Bamboo forest at around 3000 m asl.

We made it all the way to Lake Mahoma at 3000 m then returned after a thorough workout. Sadly there wasn’t time (or energy) to explore the heath forests that form the treeline, nor the endemic montane flora that lies above them. I’m intrigued enough by this landscape to already be planning a return.

I’ve completed the set! I have now seen in Kibale (drumroll please) black and white colobus, red colobus, red-tailed guenons, blue monkey, grey-cheeked mangabay, L’Hoest’s monkey, olive baboons and chimpanzees. Seven diurnal primates in one site and none of them hard to find (the nocturnal bush baby and potto are slightly trickier). It helps that so many of the groups are habituated thanks to generations of primatologists passing through.

Why are there so many primates here? I can’t give a definitive answer (though I’m sure that more informed people than me have speculated before), but suspect that part of the story lies in the age of these forests. Even those defined as primary show every sign of being in late stages of regeneration. Their canopies are short, dominated by long-lived pioneers which begin branching quite low, and with basal areas below 40 m2/ha. Whether they were cleared by humans or some catastrophic disturbance, the forests I’ve seen appear to be no more than a few hundred years old.

Why should this matter for primates? Long-lived pioneer trees have large leaves with high nutrient content, and often produce fruits which are animal-dispersed (and hence much favoured by frugivorous primates). Compare this to, for example, a much taller dipterocarp forest in Southeast Asia, where most of the leaves are practically inedible and most trees only fruit once every five or so years. Such forests are described as food deserts and primates exist at comparatively low densities.

It’s only a guess, but I can’t help feeling that the extraordinarily high diversity and abundance of primates here owes much to the relative youth of the forests.

Finally, some sad news. We heard this week that Dr Jerry Lwanga, the director of the Makere University Biological Field Station (MUBFS) at Kanyawara, and an instrumental force in the gazetting of Kibale Forest National Park, has died. I never met Dr Lwanga, but the sombre mood among the staff here is a reflection of the high regard in which he was held by all and their fondness for him. Everyone has spoken of him as a good man of impeccable probity and decency. Writing now from the field station which he founded, in the park to which he dedicated his career, it was certainly a life with many accomplishments.

* As individual mountains, Mt Kilimanjaro and Mt Kenya are taller than anything in the Rwenzori range, but they are both stand-alone peaks of volcanic origin. The Rwenzori peak of Mt Margherita is the third-tallest in Africa at 5109 m and is surrounded by a cluster of others which come pretty close.

** Apparently we saw the Rwenzori endemic purple-breasted sunbird. Or something. I include this information purely to irritate twitchers.

Field notes from Uganda 6: I am an elephant magnet

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It’s official. I am an elephant magnet. Among over 30 people here on this Tropical Biology Association field course, I’m still the only one to have seen elephants in the forest. Three times. This last encounter was by far the most unsettling.

Most of the forest close to the research station here in Kibale is logged, and of the primary forest that remains, the majority is on steep rocky slopes where extraction of timber would have been impossible. I was getting a little frustrated at not seeing any tall-stature primary forest, but that may be because the forests here seem to be relatively young.

Yesterday afternoon I decided it was time to extend the range of my excursions and, following a tip-off from one of the local PhD students, I copied his GPS base maps and headed to the southeast, descending in altitude most of the way.

At one point I almost walked into a large male chimpanzee. Crossing a boggy patch at the bottom of a gorge and watching where I was putting my feet, I was already quite close before noticing him. Startled, I scampered back a few paces then looked to see how he would respond. Not a twitch. He cast me a laconic, disinterested glance, then continued grazing on a bush. I managed to take a couple of pictures before he moved on and allowed me to pass. I’m used to meeting orang utan in the forest, when that kind of proximity to an adult male would be a dangerous situation. It’s taking a little time to adjust to how habituated these chimpanzees are.

A large male chimp finally decides to vacate the path in front of me, in no particular hurry.

Eventually the trail ended, running into a larger orthogonal path that looked like it would connect with one of the main tracks through the reserve and give me an easy trip home. This led me for a mile through some beautiful dry forest which looked to be infilled savannah dominated by Olea trees. It had a nice, open understorey and some lovely views to forested ridges beyond. Having taken two hours to get out there I was tired but it was worth the effort.

Hill forest dominated by Olea trees with some spectacular lianas. Definitely worth a two-hour hike.

Sadly my chosen trial petered out, or rather it turned into a delta of narrow interweaving and overgrown paths through tall spiny Acanthus thickets. I knew the main trail was only a few hundred metres away, but it became increasingly obvious that the paths I was using had not been made by humans. This was exactly the kind of vegetation in which I met the elephants the first time, and visibility was only a few metres. Keen not to take many risks so far from base I turned back and retraced my steps for a few miles.

The outbound trip had been over some demanding topography, but there was a ridge trail to the north that was wide and easy-going, so I took a side trail up to meet it. On the way I passed an elephant wallow and a salt lick, which meant my senses were already tingling, but it didn’t look like there had been any activity there for some time. Nevertheless I was proceeding with extreme caution.

Meeting the ridge trail was a relief, though this was soon dispelled when I found a fresh pile of elephant dung. The ground was dry so there was no definitive way of knowing whether they were ahead or behind me, and this trail was the most efficient and direct route home. I proceeded with extreme caution, practically on tiptoes, listening constantly for any sign that there might be elephants nearby. There were broken branches and a characteristic stench that I’m belatedly coming to recognise. The problem was the trail, which had high banked walls with thick scrubby vegetation on each side. It didn’t offer many means of escape.

Rounding a corner I suddenly found myself metres away from the backside of a large male elephant. My heart was already pounding, but fortunately I had seen them before they saw me, and I was still walking as silently as possible. I crept back a short way then walked briskly back down the trail, putting some fast yards between myself and the herd. It was only when I heard movement — and they were out of sight — that I broke off the trail and sped into the forest.

This stuff is no fun to run through, especially with elephants on your tail.

This stuff is no fun to run through, especially with elephants on your tail.

The forest was filled with thick undergrowth on a steep slope, but I knew that my best course of action was to head west and get to the other side of the valley, so I aimed for the sun and pulled out my machete. I dropped right back down to the valley floor, waded through the swampy vegetation (if I’ve picked up mango flies I’ll be very displeased), then hacked up the other side. Here the GPS came into its own as I was able to eventually pick up another main trail on the next ridge which led safely back to base from the other direction, completely circumnavigating the elephants. Overall the diversion added several hard miles to the return journey. I made it back at dusk, shaken, soaked in sweat and exhausted. I then bought a beer.

Surely this can’t keep happening to me?

One of our students had a memorable though less pleasant encounter with the chimps. While measuring one of the liana plots, the chimp troop came past and the group of students decided, quite reasonably, to down tools and watch. One of the girls stood on the trail directly beneath a pair of chimps engaged in enthusiastic congress when a small deposit of something warm and slimy landed on her cheek. By all accounts this was not well-received.

In all the millions of years for which our two species have shared this planet, how many times do you think that has happened?

Field notes from Uganda 5: lianas — not just for chimps to swing on

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I’ve been looking at tropical forests with fresh eyes on this trip, largely due to two books which I’ve been reading out here. The first, Second Growth by Robin Chazdon, is a compelling argument for the conservation of logged, degraded and secondary forests around the world. Far from being wastelands whose only worthwhile use is development or conversion to agriculture (hence the spread of oil palm), they should be viewed as valuable repositories of future diversity. Left to their own devices, or assisted when necessary, these forests can and will recover. It’s an important positive message regarding modern tropical landscapes. This isn’t to say that primary forests can be ignored — what remains still needs to be protected — but that regenerating forests have a crucial role to play in the future of conservation in the tropics.

The second book is Ecology of Lianas which I’m reviewing for Frontiers of Biogeography (spoiler alert: it’s brilliant). Lianas have been neglected for a long time partly due to the difficulties of measuring them, and partly due to a belief on the part of foresters that they impede tree growth, and should therefore be stripped from forests. The former problem has been removed by the publication in 2006 of a standard protocol for the measurement of lianas, encouraging many new studies and allowing researchers across the world to properly compare their results. The latter belief is being dispelled by evidence that lianas are not merely structural parasites but important engines of forest dynamics and vital for the redistribution of nutrients. Far from being deleterious, current evidence suggests that forests regenerate at at least the same rate in the presence of lianas*.

lianas

A cluster of lianas ascend into the canopy. These large lianas are a characteristic feature of old-growth forests in this area.

Inspired by the liana book, and having noticed how little work has been done in East African forests, I now have two of my student groups doing projects on them. Their broad aims are to discern how the abundance, biomass, diversity and composition of lianas change between primary, logged and secondary forests. With just over a week to collect data we’re not going to add much to the sum total of human knowledge, but we will at least be providing some baseline data, and it’s a line of enquiry which I might follow up in the future. Maybe it will be my excuse to return to Kibale one day.

While walking through the primary forest taking pictures of lianas, I happened to hear some rustling in the canopy far above me, and looked up to spot two female chimps with young! This is the first time I’ve seen chimps in the wild, and given that there were also plenty of interesting lianas in the vicinity, it seemed reasonable to stop and see what happened.

After examining me carefully, and deciding that I wasn’t a threat, the chimps began gradually descending from their lofty perch, where two nests suggested that they had spent the night. For some time they paused in the sub-canopy, then eventually worked their way down to the ground and came towards me. One crossed the path carrying her baby, which dropped off her onto the trail and sat, contentedly watching me, while she rummaged through the vegetation just out of sight. The other female stopped less than ten metres away and sat playing with her baby, entirely ignoring me.

Chimps also like lianas, which provide food and a means of movement around the canopy.

Chimps also like lianas, which provide food and a means of movement around the canopy.

The chimps here are thoroughly habituated to humans thanks to decades of study. Research assistants are constantly in the forest tracking them and observing their behaviour. It’s therefore one of the few places where one can get so close to chimps without any sign that they are troubled by human presence.

Eventually I moved off, partly because I had other lianas to look at, but also because it was beginning to feel voyeuristic. It’s a cliché to remark on the similarity of chimps to humans, but in such close proximity it’s too striking to miss, and brings home that the savannah apes and the forest apes are not so different from one another.

* I should stress that liana tangles in seriously degraded forests are a different matter. In such cases they can arrest succession and form alternative stable states that make it difficult for the forest to recover.