Fruit-cutting ants

A nice piece of natural history from the latest Ecological Entomology.

The workers of leaf-cutting ants (Atta) fall into two categories — minors, which do the forgaing, and majors, which are more involved in colony defence. But Sophie Evison and Francis Ratnieks at Sheffield have spotted that Brazilian leaf-cutters will also chop fruit (in this case mango) into bits and cart it back to the nest.

But the fruit-cutting is done by the majors - presumably because their jaws are big enough to handle three-diimensional stuff like mango, whereas small jaws are only good for leaves. So we can add a new job to the majors' task list.

The question that occurred to me was - what happens to this fruit in the nest? Leaf-cutters can't digest leaves, so they feed it to fungus in the nest, then eat the fungus. But most of us can digest mango, so does fruit bypass the fungus farm and get eaten raw?

I frass, you frass, he frasses, they frass

A couple of weeks ago, Sara and I were talking, as you do, about the word 'frass', which is the technical term for insect poo.

She said it sounded more like a verb than a noun. It hadn't occurred to me that different types of word sounded different, and I wondered whether they did.

Well, they do. I was chatting with some researchers on Friday, and they mentioned work by Morten Christiansen at Cornell and his colleagues on just this topic. Last year, they published a paper showing that nouns and verbs do cluster together in phonological space.

But the categories aren't rigid. There are 'nouny nouns', which are found in the middle of noun space, but also 'verby nouns' which are closer to verbs. Likewise, there are verby verbs and nouny verbs.

The team did experiments showing that people process nouny nouns more quickly than verby nouns. For example, they are quicker to grasp the meaning of:

The curious young boy saved the marble that he found on the playground.

than

The curious young boy saved the insect that he found in his backyard.

because 'marble' is a nouny noun, whereas 'insect' is more verby.
The same difference was shown between sentences containing verby verbs, such as 'amuse' and nouny verbs, such as 'ignore'.

Last year's paper cites earlier studies showing that 'adults are more likely to use a nonsense word as a noun when it is multisyllabic'. So I would guess that 'frass' would fall amid the verby nouns.

Christiansen et al argue that these cateogries exist in other languages besides english, and suggest that learning these categories is one of the steps in acquiring language.

From idle speculation to scientific resolution - just how I like it.

Batty like a FoxP2

Back in 2001, FoxP2 was the first gene to be linked to human language. The gene was hunted down by studying a British family with extreme difficulties in forming speech. I wrote about (paywall) this work at the time.

Since then, there's been a bunch of studies on the gene - revealing, for example, relatively large differences between the human sequences and that of other primates. But it was thought that, humans aside, there was relatively little variation in vertebrates.

Well, just goes to show how taxonomically restricted our genetic knowledge is, because a Sino-Anglo team has just discovered that the gene varies lots in bats, which don't talk, but do echolocate. There's a news report about their PLoS One paper here.

To see how the variation between closely related bat species really does dwarf that seen between much more distantly related beasts, check out this figure.

Nice. But FoxP2 is not giving up all its secrets just yet. The pattern of evolution - what's been selected for what - is not clear from the sequences, there's just a lot of difference. And comparing bat sequences with other species doesn't help much

Evidence from birds, which likes bats and people show vocal learning, is shows 'no evidence of specific mutations associated with vocal learning abilities...if variation in FoxP2 has a role in vocal learning then it is not straightforward'. Nor are there clear similarities with whales, which also vocal learn and echolocate.

So what is FoxP2 uP2? If it's a 'language gene' it looks as if it's role isn't in what we think of as the clever stuff of language - grammar and syntax - but in the mechanics: the motor control needed to produce tightly controlled sounds, say. But, as far as I can tell, there's no hard and fast links between the gene sequence and this ability. It's just involved somewhere down the line.

One clue is that FoxP2 is a transcription factor - it's product controls the activity of other genes. Maybe this is why comparing species gives few clues as to how its sequence relates to its function: because it's an information processing gene and not making something like haemoglobin, the structure of which is jolly important, maybe its free to vary more, and to mean different things to different animals.

I don't know how much we know about the genes it regulates - I couldn't see anything in the paper, so I'm guessing not much.

Underground networking

Todays's Nature contains a News Feature by me (behind a paywall, I'm afraid), looking at the possibility that mycorrhizal fungi transfer nutrients between plants, and in the process undercut the above-ground competition between plants by robbing the rich to feed the poor - subsidizing plants less able to photosynthesize.

How, why and whether they do this is still uncertain and occasionally controversial. But everyone seems to accept that mycorrhizal networks do exist - namely, that a single fungus can link many plants, potentially of different species, creating a arena for a rich range of ecological interactions. It's just we're not sure what they are. But a bunch of people are doing their damnedest to find out. Mycorrhizal ecology looks like a funky (and fungi) field right now.

For a more technical (than my piece), but freely accessible introduction to this field check out this TREE paper.

Why you will never get everyone to agree with you

Here’s what the recent Nature Neuroscience paper ‘Neurocognitive correlates of liberalism and conservatism’ (See here for one of the many news reports) made me think.

This looks like the (one of the) neural manifestation of a personality axis, such as bold/timid, extrovert/introvert. People and animals spread out all over these — reflected in animals in how quick they are to explore new environments, how far they disperse, and so on. You could probably redefine liberalism/conservatism in terms of these (people probably already have).

So the big question, I think, is: what maintains this diversity in a population? It could be frequency-dependent selection — it becomes more advantageous to be liberal if you’re surrounded by conservatives, and vice versa. Seems unlikely.

More plausible is that it’s balancing selection: there are some environments and tasks that favour a liberal approach, and some that favour conservatism. In great tits, for example, bold, far-dispersing males do better after mild winters, when territories are at a premium, and food is plentiful, whereas stay-at-homes do better after harsh winters. For females, the reverse is true.

So no one strategy can take over. And personality in these birds has a strong heritable component. So, in a variable environment, where genes don't know which sex of bird they're going to be on (unless they're on the females-only W chromosome in birds, or the male-only Y in mammals), a braod range of personality types can persist.

It seems plausible that something roughly similar might be at work in people — the benefits of reaching out, trying new stuff, versus the benefits of staying put and consolidating will depend on the environment. Question here is, why can’t each of us (or each great tit, for that matter) work that out, and adapt to any environment? What is it about our brains, and the genes (and environments) that make them constrains us to occupy our place on the personality axis?

It seems, anyway, that if our politics come from inside us, as well as being a consequence of what the world does to us, we can’t expect political extinction for either liberals or conservatives, just as there are bold and timid great tits.

Of course, when it comes to voting, there’s lots of other stuff at work. It struck me that this is a US study, where, because the different parties don’t offer anything different in the way of economics, peoples’ voting decisions may be more swayed by all that ‘values’ stuff that tickles these particular ‘am I up for this?’ bits of the brain. Also I’m guessing that those studied were students, and occupied a narrow socioeconomic band. It’s perfectly possible to be a left-wing conservative, but more likely if you’re working class, I’d guess.

South Bank Wayang

In non-science-related news, there's a piece by me in today's Guardian about the all-night Javanese shadow puppet play (wayang), including the South Bank Gamelan Players, at the festival hall tomorrow. I doubt it's sold out.

In other news, the Independent newspaper recently put ITBOAH on its list of 10 best nature books. Which is nice. No sign of this online, but Oliver Morton has reproduced the list (which includes his own Eating the Sun) on his photosynthesis-related blog.

Fibonacci watch

One of my partner Sara's bugbears is that all efforts to group art and maths together lazily invoke the Fibonacci sequence (Something, I admit, I've been guilty of myself.)

But my crimes pale next to this absolute humdinger, from the August issue of The Wire. This is Philip Sherburne writing about techno musician and DJ Ricardo Villalobos.

When it comes to rhythm, Villalobos is certainly one of the canniest producers in contemporary electronic dance music. His youthful training in Afro-Latin percussion explains some of his sense of timekeeping, but it doesn't necessarily address the uncanny quality of so many of his beats, which take shape with the same kind of natural/unnatural ease with which a sunflower sprouts seeds according to the Fibonacci sequence.

Let's enjoy that again.

the same kind of natural/unnatural ease with which a sunflower sprouts seeds according to the Fibonacci sequence.

Eh?

Other egregious Fibonaccisms welcome.

Autumn colours and aphids

In a previous life, before I became a successful, respected and well-balanced science writer, I did a PhD on the evolution of soldier castes in aphids. Happy days (not).

In this life — in 1996, to be exact — I travelled to an entomology conference in Florence. There, at a session on aphid biology, a fellow grad student and more talented researcher than myself called Sam Brown gave a presentation, coauthored with his supervisor Bill Hamilton, on the idea that the autumn colours of trees were a signal to marauding aphids of the strength of their antiherbivore defences.

Bright colours, their argument went, were an honest signal: only well-resourced trees able to make lots of the secondary compounds that plants use to make themselves unpalatable to herbivores would be able to make them. And aphids flying around in the autumn, looking for somewhere to lay their overwintering eggs, would shy away from such vivid displays.

The debate on the worth of this neat hypothesis has rumbled along for more than a decade now. Sceptics have pointed out that yellow pigments were there all along, but are only revealed when the leaf takes back it’s chlorophyll — leaves don’t turn yellow, they unturn green. Also that red pigments have other potential uses, centred on protecting the leaf as the plant takes it apart, chemically speaking. The latest update comes from Lars Chittka and Thomas Döring, two researchers on sensory ecology writing in PloS Biology.

To put it crudely, C and D’s piece plugs a forthcoming paper (this link wasn’t working when I checked) by them looking at colour vision in aphids. They find that Brown and Hamilton might have been deceived by their human’s-eye view. Aphids (and all other herbivorous insects looked at so far) don’t have good vision in the red — so red leaves wouldn’t look anything special to them. And yellow is powerfully attractive — it tickles their green receptors even more so than green itself, and brings insects flocking: ‘If trees wanted to deter herbivorous insects using color, yellow leaf coloration is about the worst strategy they could pick,’ they write.

The piece does such a good job of pouring cold water on the notion that autumn colours are signals that their final (inevitable) conclusion — the good old cry of ‘more research is needed’ rings a little hollow. Speaking as a rampaging adaptationist, who thinks that Hamilton has a good claim to having been the most important evolutionarybiologist since Darwin, I think that’s a bit of a shame, but there you go, beautiful theories, ugly facts and all that.

The essay also has some nice bits of history, and a lovely first sentence: ‘Most living things don't turn beautiful when they senesce’. But some editor should have stopped the use of ‘fascinating’ twice in the first paragraph. I can work out whether something is fascinating or not. (And while we’re about it, can we have a ten-year moratorium on the use of ‘intriguing’ in science journalism? It’s just ‘interesting’ wearing a false moustache.)

Spontaneous order, fungal networks, and circuses

You wait ages to feel moved to post, and then three things come along at once. In no particular order…

Biological modularity can emerge as a spontaneous, self-organized process, say Ricard Solé and Sergi Valverde in J. R. Soc. Interface. By modularity they mean particular sets of interactions in the great web of biochemistry (rather than, say, organs):

Modularity is particularly obvious in cellular networks, where it can be detected at the topological level. These networks include the webs of interactions among proteins, genes, enzymes and metabolites or signalling molecules.

Such a trend seems to call for an adaptive explanation. In particular, what seems to demand explanation are ‘motifs’ in these networks

patterns of interconnections occurring in complex networks at numbers that are significantly higher than those in randomized networks.

Solé and Valverde cite a couple of adaptive explanations “based on a genetic programming approach”. But they don’t agree with them.

Instead, they say such modularity is the inevitable consequence of evolution by gene (or genome) duplication (“the driving force behind the evolution of complex organisms”, they say) followed by divergence, as evolution tinkers with the newly enlarged network of interactions (letting natural selection back in, it looks like)

I’ve clearly, as is my wont, become aware of this debate somewhere in the middle — the paper cites several is-modularity-evolution-or-is-it-self-organization? papers from the past few years. But, as far as I can tell, Solé and Valverde are saying that this is the first explanation for such modularity based on “fundamental, dynamical rules”.

In other network news, Proc R Soc B has just published a paper by Daniel Bebber et al. looking at fungal networks.

they have evolved to explore and exploit a patchy environment rather than ramify through a three-dimensional organism. Unlike all the other biological transport systems studied, the fungal network is not part of the organism, it is the organism.

The challenges such a fungal mycelium faces are to explore its environment, exploit resources, transport them around the rest of the organism, and to be sufficiently robust to resist physical damage and the many fungus-eaters in the soil.

To investigate how fungi meet such challenges, they grew Phanerochaete velutina in the lab, growing it out from an inoculated lump of wood towards other lumps of wood. They found that the fungus began in exploratory mode, sending out lots of narrow filaments. But as it completed searching its environment it consolidated its resources into fewer, bigger bundles of hyphae, growing between maor resource patches, with more exploratory filaments in new territory, and crosslinks to provide some redundancy in the case of network damage. “Netowrk development”, say Bebber et al.

involves over-production of links and nodes in the exploratory phase, followed by selection and positive reinforcement of some links and recycling of the remainder during the consolidation phase … A
similar sequence of events is apparent in the development of other biological transport networks including those formed by acellular slime moulds [and] foraging ant trails … and may well represent a universal feature of self-organized biological networks. However, in each of these systems, the final network structure is likely to represent a context-specific balance between the need for efficient transpor t, cost and robustness.

In other words, they’re stressing the diversity of different structures produced by flexibility and responsiveness to environmental variation, as much as whatever general laws such networks might have.

Philip Loring (who I believe blogs here) approaches questions of resilience, connectedness and persistence from a different angle in Ecology and Society. He proposes the circus as an icon of resilience, in that it has retained its identity while changing its contents — i.e. getting rid of freak shows and (mostly) animal acts.

Through the many forms they have taken over the last 150 yr, circuses have changed significantly while sustaining a singular identity. As a successful and enduring social system, their intriguing history exposes the nuances of sustainability theory, from resilience to pathologies, and illustrates that sustainability requires a complex dynamic between identity, tradition, and change.

The article, to my mind, contains a bit too much on the history of the circus, without exploring the implications of the circus-as-sustainability metaphor. Also, while ‘circus’ has survived for 200 years, most individual circuses haven’t. This is fine for institutions and systems, but not so much for species and ecosystems. But it’s a nice comparison.

Survival of the likeliest?

There's a feature by me in the current PLoS Biology (and it's free!) on whether natural selection can be explained by the laws of physics, specifically thermodynamics and statistical mechanics. This looks at work of Roderick Dewar on Maximum Entropy Production (MEP), Adrian Bejan's constructal theory, work by Eric Smith at Santa Fe on self-organization and metabolism, and a few other things. The basic idea is that, by looking at the flows of energy and matter, we can predict and quantify the path and results of evolution.

This is something I've been thinking about for a couple of years — I put a bit about it in the first draft of ITBOAH, but took it out, 'cos it wasn't really working. And I wrote a piece for Nature looking at MEP from a more climate- and ecological viewpoint, which didn't go so much into the evolutionary implications. So I'm very glad that this is finally seeing the light of day.

What I did on my holiday

I've just got back from three weeks on holiday in Andalucia. Two things I learnt:

Trenhotel good. If you don't dilly-dally, you can eat lunch in London one day, and in Seville the next, without leaving the ground. The overnight journey, from Paris to Madrid, is comfy and fun (cf flying) – there's a bar and restaurant on the train. The mighty seat61.com has all the details.

Plasticultura bad. When I saw vegetables in my local supermarket from Spain, I had, I suppose, a dim image of a happy campesino weidling a mattock and whistling a song. In fact, it seems that they are grown in one of a never-ending series of plastic greenhouses that, in eastern Andalucia (around Almeria) fills just about every bit of land between the sea and the mountains.

There's a danger in knee-jerk disapproval of the unsightly — I'm sure there are outdoor forms of farming that have just as much environmental impact, but, because they fit our idea of what farmland should look like, don't make you as depressed as a sea of plastic. And there are arguments that, where we farm, we should do it as intensively as possible, so that is uses the minimum of land and leaves more for nature (whatever one means by that). (Although in a country like the UK, where farmland and countryside are the same thing, this would be tricky.) Plasticultura, or invernaderos, however, do seem to take out more water, and put back more nitrates, than the land can support. Plus they are hellish places to work (although not so hellish that no one wants to work there).

To find out more, try this article from the Ecologist for more on water, the environment and farming in southern Spain, this from John Vidal on the Spanish drought, this lecture by Felicity Lawrence for intensive farming in general, and here (recommended) for photos of plasticultura farming.

I shan't be buying Spainsh veg any more, thus making my winter diet even more cabbage-based than previously.

Oekologie #5

Jeremy Bruno over at the Voltage Gate has done an erudite job on this month's Oekologie blog carnival (my own hosting effort is here).

Guardian podcast

I'm on this week's Guardian science podcast, talking about D'Arcy Thompson, polymathy (is that a word?) and ITBOAH with Alok Jha and the other young rowdies.

Father and son

Among the many, many stories I've recently written for news@nature.com recently is one about changing dates of the UK mushroom season. There's been a huge effect in response to warming — the autumn season is twice as long, and some mushrooms are popping up in spring, as well as autumn.

This is a lovely example of you-never-know-when-it'll-come-in-handy data collection. The data — ranging from 1950-2005 — were collected by Edward Gange, stonemason by day and fungal recorder for the Wiltshire Natural History Society in his spare time. The lead author on the paper is his son, ecologist Alan Gange. Isn't that nice?

Another good thing about this piece is that it gave me a gave me a chance to interview Andy Overall, one of whose fungus forays I attended last year.

Back in the dim'n'distant, I had a lot of fun writing a longer piece for Nature about ecologists using data collected by amateurs to measure the effects of climate change on living things. If you ask me, this is probably the most important ever non-specialist contribution to science. Always glad to hear of any other candidates, though.

The coming era of jellyfish ascendancy

I admit it, my devotion to the work of George Monbiot (or The Monb, as he's apparently known in some environmental circles) borders on the unhealthy.

But this piece on marine conservation, and the overfishing of top predators such as sharks, is really excellent.

The Spanish fishing industry, he writes, is "traditionally dominated by Galician fascists". There's no fascist like a Galician fascist.