Social termites team up with non-relatives

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This post was chosen as an Editor's Selection for ResearchBlogging.orgIn social insects, colonies of hundreds or thousands of workers and soldiers forgo reproduction to support one or a few “reproductives” — drones and a queen. In most cases, this isn’t as selfless as it might seem. Because the workers in a colony are all offspring of the queen, they’re really reproducing through her — because the queen shares genes with the workers, when she reproduces it contributes to their evolutionary fitness.

This is called kin selection, and in many cases it’s a good explanation for the way the interests and behavior of individual workers are overridden by the interests of the colony. There are, however, exceptions — and an open-access paper in the latest issue of PNAS describes what looks like a good case: mergers between unrelated colonies of termites.


Zootermopsis nevadensis, a social insect inclined to negotiated settlements. Photo by BugGuide/ Will Chatfield-Taylor.

The termite Zootermopsis nevadensis lives in small, socially-stratified colonies that tunnel through rotting logs. Each colony has a pair of reproductive individuals, a king and queen, served by sterile workers and soldiers. Multiple unrelated colonies usually nest in a single log, and when they encroach on each other’s territory, something interesting happens — they merge.

In what the authors refer to obliquely as the “interaction” that precedes a merger, the king and queen of one or both colonies may die. Mergers occur in the aftermath, as workers from the two colonies began to work in concert, and one or a few of them become replacement reproductives. This ability of sterile workers to start reproducing in the absence of a king and queen is unique to termites. DNA analysis shows what happened after mergers — new reproductives could arise come from either or both colonies, and that in some cases they interbred.

It’s this possibility to become genetically invested in the newly merged colony, the authors say, that motivates workers from two unrelated colonies to work together. If this is the case, it means that kin selection is not what keeps merged colonies together. Group selection might be a better explanation. Kin selection is often contrasted with group selection, in which unrelated individuals sacrifice their own interests to those of a larger group, so that their colony can better compete against rival colonies. In a classic 1964 Nature paper [$-a], John Maynard Smith discussed the conditions under which kin selection operates well:

By kin selection I mean the evolution of characteristics which favour the survival of close relatives of the affected individual, by processes which do not require any discontinuities in population breeding structure.

And contrasts them to conditions necessary for group selection to work:

[Under group selection] … If all members of a group acquire some characteristic which, although individually diadvantageous, increases the fitness of the group, then that group is more likely to split into two, and in this way bring about an increase in the proportion of individuals in the whole population with the characteristic in question. The unit on which selection is operating is the group and not the individual.

The ecology of Zootermopsis nevadensis may set the stage for group selection to overpower kin selection. With many small colonies competing for a single rotting log, the benefits of possibly contributing to the reproduction of a larger, more competitive colony make mergers worthwhile. Something similar has been documented in ants, which can form supercolonies of unrelated colonies if there is some external threat (another ant species) to force them to band together — you can find discussion of a recent paper on this case over at Primate Diaries.

References

SMITH, J. (1964). Group selection and kin selection Nature, 201 (4924), 1145-1147 DOI: 10.1038/2011145a0

Johns, P., Howard, K., Breisch, N., Rivera, A., & Thorne, B. (2009). Nonrelatives inherit colony resources in a primitive termite Proc. Nat. Acad. Sci. USA, 106 (41), 17452-6 DOI: 10.1073/pnas.0907961106

The birth of “scientific” management

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Read this last weekend, but didn’t get a chance to comment: online at The New Yorker, Jill Lepore reviews Matthew Stewart’s The Management Myth: Why the Experts Keep Getting It Wrong. Lepore digs into the origins of “scientific” management approaches that emerged in the early 20th century, aiming to wring the maximum productivity out of every worker. The field was essentially created out of whole cloth by one Frederick Winslow Taylor, who made up data, trafficked in racist stereotypes, treated industrial workers like livestock to be trained, and charged companies ridiculous fees for the service:

How did Taylor arrive at forty-seven and a half tons [as the amount of iron one man could load in a day] for Bethlehem Steel? He chose twelve “large, powerful Hungarians,” observed them for an hour, and calculated that, at the rate they were working, they were loading twenty-four tons of pig iron per man per day. Then he handpicked ten men and dared them to load sixteen and a half tons as fast as they could. They managed to do it in fourteen minutes; this yields a rate of seventy-one tons per man per ten-hour day. Taylor inexplicably rounded up the number to seventy-five. To get to forty-seven and a half, he reduced seventy-five by about forty per cent, claiming that this represented a work-to-rest ratio of the “law of heavy laboring.” Workers who protested the new standards were fired.


Cheaper by the Dozen first-edition cover. Image from Wikipedia.

The saner practitioners of scientific management turn out to be none other than Frank and Lillian Gilbreth, whose efficiency-oriented family life is chronicled in Cheaper by the Dozen, a book I loved in about sixth grade. What doesn’t come through in the book is that Lillian was a substantial contributor to Frank’s thinking and writing about worker efficiency, and may have ghostwritten one or more of his books. This moment, I think, sounds like the Frank and Lillian Gilbreth I know from the CBTD:

Onstage, Frank was challenged by Emma Goldman. He was pointing to a chart illustrating the hierarchical relationship between the foreman and the worker. “There is nothing in scientific management for the workman,” Goldman shouted. “The only scheme is to have the workman support the loafers on top of him.” Lillian leaned over and whispered something to Frank, who cheerfully turned the chart upside down.

“Management,” as a separate academic discipline has always struck me as basically bunk. But the Gilbreths, at least, seem to have had legitimately good intentions.

Not sure that’s a problem with the website

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Via Slog: There have been some glitches in the launch of the new GOP.com (to which I refuse to link).

Among the problems were the posting of administrator passwords, a list of GOP accomplishments that ended in 2004 and a “future leaders” section that was devoid of material. In addition, the site was inaccessible for much of the day.

Video of yucca pollination

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ResearchBlogging.orgWith permission from my doctoral advisor, Olle Pellmyr, I’ve just uploaded a unique video to Vimeo: a yucca moth laying eggs in, then pollinating, a yucca flower. I don’t know why I didn’t think of this earlier — it’s great footage, and deserves to be seen more widely.

A female yucca moth mates, then collects pollen from a yucca flower in specialized mouthparts. She carries it to another flower where, as shown in the video, she drills into the floral pistil with her ovipositor and lays eggs inside, then climbs to the tip of the pistil and applies pollen to fertilize the flower. When the flower develops into a fruit, the eggs hatch and the caterpillars eat some of the seeds inside.

Yuccas and yucca moths are completely dependent on each other [PDF] — nothing else pollinates yuccas, and the moths have no other source of food (they don’t eat as adults). Recently, the Pellmyr lab has shown that this interaction may be leading to speciation in one yucca species, the Joshua tree — Joshua trees pollinated by two different species of yucca moths have differently-shaped flowers [PDF], but these two tree types may not be totally genetically isolated [PDF]. I’ve written about this work before — for more information about the interaction, check out Olle’s publication page.

References

Godsoe, W., Yoder, J., Smith, C., & Pellmyr, O. (2008). Coevolution and Divergence in the Joshua Tree/Yucca Moth Mutualism. The American Naturalist, 171 (6), 816-23 DOI: 10.1086/587757

Pellmyr, O. (2003). Yuccas, yucca moths, and coevolution: A review. Annals of the Missouri Botanical Garden, 90 (1) DOI: 10.2307/3298524

Smith, C., Godsoe, W., Tank, S., Yoder, J., & Pellmyr, O. (2008). Distinguishing coevolution from covicariance in an obligate pollination mutualism: Asynchronous divergence in Joshua tree and its pollinators. Evolution, 62 (10), 2676-87 DOI: 10.1111/j.1558-5646.2008.00500.x

First step to mutualism doesn’t look so friendly

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This post was chosen as an Editor's Selection for ResearchBlogging.orgAnt-plant protection mutualism is a widespread and elegant species interaction. How do species strike bargain like this, requiring specialized behaviors and structures in each partner, in the first place? A new report in The American Naturalist suggests an answer: maybe ants took the initiative [$-a].

In exchange for protection from herbivores and competitors [big PDF], “myrmecophytic” host plants grow hollow structures called domatia and often produce nectar to shelter and feed a colony of ants. This mutualism is really a sort of negotiated settlement between the partners; both ants and plants do what they can to get the most out of the interaction. We have evidence in some cases that host plants cut back support for ants if there aren’t any herbivores around; and, in other cases, that ants prune their host plants to prompt the growth of more domatia.



Domatium diversity: Ant domatia on Acacia (above) and Cordia nodosa (below). Photos by Alastair Rae and Russian_in_Brazil.

So it isn’t entirely surprising that there might be cases where that bargain hasn’t been established yet, and that’s what the new paper reports. The observation turned up in connection with one of the most interesting forms of the ant-plant mutualism: the “devil’s gardens” of the Amazonian rainforest. Devil’s gardens are created by colonies of the ant Myrmelachista schumanni, which attacks possible competitors to its preferred host [$-a], Duroia hirsuta, leaving patches where nothing but D. hirsuta grows.

Clued in by native research assistants, the group studying the devil’s garden interaction discovered that trees growing at the edge of a garden are often afflicted with swollen, distorted trunks. Cutting into the swellings, they found them riddled with passages and populated by M. schumanni. The trees in question are not known as myrmecophytes, and it’s not clear that they receive any benefit from hosting ants. In fact, the authors report that ant-occupied trunks are weakened, and prone to breakage under their own weight or under heavy wind.

The paper doesn’t present direct evidence that the ants create the galls, but as the authors explain, this seems likely — M. schumanni kills its hosts’ competition by injecting them with formic acid, which parallels the irritants other gall-making insects inject into their host plants. It make sense that gall-making might have started as ants’ attempts to kill off trees that are too big to succumb to formic acid outright, but respond to it by growing galls like scar tissue. Furthermore — and this is pure speculation, of course — this looks like a first evolutionary step toward true ant-plant mutualism. Domatia may have originally evolved to redirect ants from more damaging gall-making, and since ants are naturally territorial about their nests, it might not take much behavioral change before they end up protecting their host.

References

Edwards, D., Frederickson, M., Shepard, G., & Yu, D. (2009). A plant needs ants like a dog needs fleas: Myrmelachista schumanni ants gall many tree species to create housing. The American Naturalist, 174 (5), 734-40 DOI: 10.1086/606022

Frederickson, M., Greene, M., & Gordon, D. (2005). “Devil’s gardens” bedevilled by ants Nature, 437 (7058), 495-6 DOI: 10.1038/437495a

Janzen, D. (1966). Coevolution of mutualism between ants and acacias in Central America Evolution, 20 (3), 249-75 DOI: 10.2307/2406628

Oh, and by the way …

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I’m gay.

I came out of the closet just a few months ago — but that’s a story I probably won’t recount in any detail on D&T, which has never included much detail about my personal life, and probably never will. I debated whether to write even a brief post like this, and finally decided to do so only because this is a part of my personal experience that colors what I discuss here. And, what the heck, today is National Coming Out Day. Cheers.

PS: For blogging on the politics and personal issues of gay identity, see Dan Savage and Andrew Sullivan, in that order. They’ve strongly shaped my own views in my journey so far, and are much more eloquent and authoritative than I could hope to be. For discussion of homosexuality in an explicitly Mennonite context, see PinkMenno.

Update, added 9 November 2010: Further explanation for my decision to come out online may be found here.

Aiming at a moving target with a shaky pistol: Evolution in a random, changing world

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ResearchBlogging.orgBiologists can become distinctly cranky when we hear evolution described as “random.” This is because evolution isn’t random — it’s undirected. Although it acts on mutations that turn up randomly, natural selection is highly nonrandom, in that (all else being equal) traits that help their owners make more babies are always the ones that spread through a population.

However, even if natural selection predictably aims for the same target, that target is not necessarily fixed. The most obvious case of this is in the coevolution of interacting species, where adaptation by one forces adaptation in the other. This is a field of study in its own right; but one recent innovation is a theory paper by Gandon and Day, which tracks changes in the “fitness landscape” resulting from adaptations and counter-adaptations [$-a]. (For more detail on the paper, see Coevolvers.)


Ground finches (Geospiza fortis) with big beaks might be favored this year, but what about next? Photo by kookr.

Empirical studies have shown that selection’s target can move in unexpected ways, too. One of the best examples of this turned up in the course of the ongoing, decades-long study of finches on the Galapagos Island Daphne Major. As rainfall on the island fluctuated from year to year, the mix of available seeds changed as well, and the finches’ beaks — the size of which determines what seeds are easily cracked and eaten — evolved to keep up [$-a]. The resulting evolutionary path looks like a drunkard’s walk, and the study’s authors, Peter and Rosemary Grant, put the word unpredictable right in the title.

Making things still more complicated, there is actually a random component to the effects of natural selection. That is, in the real world, advantageous traits may not automatically result in greater fitness — they result in greater expected fitness. Last year, Sean Rice published a mathematical model of evolution in which fitness is a random variable. He found that greater variation around the expected fitness can increase the strength of natural selection; that is, more uncertainty about the relationship between fitness and a given trait may actually make that trait adapt more rapidly. In a just-published extension of this work, Rice and Anthony Papadopolous examined the effect of random migration among different populations on adaptive evolution in each population, and found that greater variation in migration rates can reduce the effect of migration on local evolution.

Introducing all this randomness into our view of evolution doesn’t necessarily make evolution unpredictable. As an excellent recent Radiolab episode discusses, there are patterns to be extracted from randomness. It takes more work — larger sample sizes, longer-term studies — for these patterns to become apparent. Yet it’s clear that this is work we’ll have to do in order to understand biological systems.

References

Gandon, S., & Day, T. (2009). Evolutionary epidemiology and the dynamics of adaptation Evolution, 63 (4), 826-38 DOI: 10.1111/j.1558-5646.2009.00609.x

Grant, P., & Grant, R. (2002). Unpredictable evolution in a 30-year study of Darwin’s finches Science, 296 (5568), 707-11 DOI: 10.1126/science.1070315

Rice, S. (2008). A stochastic version of the Price equation reveals the interplay of deterministic and stochastic processes in evolution BMC Evolutionary Biology, 8 (1) DOI: 10.1186/1471-2148-8-262

Rice, S., & Papadopoulos, A. (2009). Evolution with stochastic fitness and stochastic migration PLoS ONE, 4 (10) DOI: 10.1371/journal.pone.0007130

Horchata!

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New track, from the upcoming Vampire Weekend album, now available for free download.

Wait, let me get this straight …

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The compromise that might actually get us a nationwide, publicly-financed insurance plan — what many are calling a “public option” — is to make it optional? Well, at least the crazy is flowing the way I’d prefer, for once.

Snark aside, the compromise is to make the public option “optional” at the state level — states can opt out if they want, presumably through legislative action. Sounds fine to me. The point of a public option is to make it big, and the big blue states — California, New York, &c — won’t opt out. It’ll be (mostly) smaller, hyperconservative states that — Mississippi, Alabama, Idaho — are most likely to do so. That’s unfortunate, because these are also poor states, with lots of citizens who would benefit from public health insurance — but at least their legislatures can be crazy on their own, and not derail it for the rest of the country.

This is also one more reason I’d better find a postdoc somewhere outside of Idaho.

Empirical pacifism?

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ResearchBlogging.orgSlogger Charles Mudede points to a new epidemiological study on the effectiveness of carrying a gun for self defense [$-a]. Not only does packing heat fail to help in the event of an armed robbery,

… individuals in possession of a gun were 4.46 (P < 0.05) times more likely to be shot in an assault than those not in possession. Among gun assaults where the victim had at least some chance to resist, this adjusted odds ratio increased to 5.45 (P < 0.05).

That’s right, carrying a gun increases the odds that you’ll be shot by an armed assailant. It also increases the odds that you’ll be shot fatally, by about 4.23 times. The authors interviewed 677 gun assault victims in Philadelphia, from between 2003 and 2006, with 648 interviews drawn from the general population in the same period as a control. (If you can’t get to the paper on the journal website, Mudede links to a ScienceDaily article about the result that gives more detail.)

Here’s empirical evidence that returning violence with violence (or having the ability to do so) doesn’t lead to better outcomes — unless, of course, you’re of the school of thought that it’s better to be shot than to lose your wallet or your pride. I doubt this will have much impact on the U.S. political conversation about guns and gun control, because as I’ve noted before, this is not a subject about which people think rationally. Nevertheless, it’s a statistic I intend to remember for the next time I’m asked to defend the ethics of nonresistance.

Reference

Branas, C., Richmond, T., Culhane, D., Ten Have, T., & Wiebe, D. (2009). Investigating the link between gun possession and gun assault American Journal of Public Health DOI: 10.2105/AJPH.2008.143099