Tag Archives: Research Blogging

Pollinating birds leave plants in the lurch

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ResearchBlogging.orgPlants’ ancient relationship with animal pollinators is pretty crazy, when you think about it. On the one hand, it gives plants access to mates they can’t go find on their own, and it’s more efficient than making scads of pollen and hoping the wind blows some onto another member of your species. On the other hand, it can leave a plant totally dependent upon another species for its reproduction.

This catch is probably why lots of plants still use wind pollination strategies, or reserve the option to pollinate themselves if animals don’t do the job for them. Avoiding complete dependence on animal pollinators is likely to become more important in the modern era, as human disruption of the environment amplifies the inherent risk of entrusting your reproduction to another species [$a], a study in the latest issue of Science shows.

A flower of Rhabdothamnus solandri, waiting for pollinators who may never show up. Photo by Tonyfoster.

Sandra Anderson and her coauthors examined the health of populations of Rhabdothamnus solandri, a forest shrub native to the North Island of New Zealand. The flowers of R. solandri are classic examples of the pollination syndrome associated with birds—bright red-orange, with long nectar tubes. Rhabdothamnus solandri is incapable of self-pollinating, because its The flowers attract three native bird species, the tui, the bellbird, and the stitchbird. Thanks to human activity, all three of these birds “functionally extinct” in most of the range where R. solandri grows.

The bellbird and the stitchbird were eliminated from much of the North Island in the Nineteenth Century as European colonists cleared forests for farmland and introduced cats, rats, and dogs that preyed on the native fauna. Tuis have persisted, but tend to stay in the upper forest canopy—possibly to avoid rat predation—and don’t visit lower-growing shrubs. However, all three birds are still living as they did before Europeans arrived on two island nature preserves just a few kilometers off the North Island’s shores. This creates an inadvertent experiment in pollinator loss, allowing Anderson et al. to compare R. solandri populations on the mainland with those on the preserve islands to see how the plant gets on without its pollinators.

The short answer is: not well.

The three principle pollinators of R. solandri, the tui, the bellbird, and the stitchbird. Only the Tui is still common in most R. solandri habitat. Photos by kookr, angrysunbird, and digitaltrails.

To test whether R. solandri‘s reproduction is limited by pollen supply (as opposed to water or nutrients), the authors compared flowers that were either enclosed to prevent pollinator access, left open to natural pollination, or pollinated artificially. On the islands, plants left open set about as much fruit as plants pollinated by hand—but on the mainland, plants pollinated by hand set much more fruit than those left open. Mainland plants also produced smaller fruits, with fewer seeds per fruit, than island plants. The enclosed flowers set very little fruit, so it seems clear that pollen is the limiting factor for island and mainland R. solandri populations, and mainland populations aren’t getting enough.

The age structure of island and mainland R. solandri populations bears this out. Anderson et al. surveyed the island and mainland sites and counted the number of “adult” shrubs in a given area relative to recently sprouted seedlings. Island and mainland sites had similar densities of adult shrubs, but mainland sites had much lower densities of seedlings. It looks very likely that R. solandri populations on the North Island mainland are in decline as a direct result of losing pollinator services.

As Cagan Sekercioglu points out in an invited commentary [$a], this study demonstrates that species’ ecological roles can be strongly compromised even if they don’t go extinct. Tuis and bellbirds are not considered particularly endangered, and the stitchbird is classified as “vulnerable,” the lowest level of “threatened” under the system used by the International Union for the Conservation of Nature. Yet these birds’ local losses and adaptation to human activity have left R. solandri without adequate pollination services. Conserving biodiversity requires more than preventing extinction—but it can be quite a bit harder to preserve important relationships between species such as this one.

References

Anderson, S., Kelly, D., Ladley, J., Molloy, S., & Terry, J. (2011). Cascading effects of bird functional extinction reduce pollination and plant density. Science, 331 (6020), 1068-1071 DOI: 10.1126/science.1199092

Sekercioglu, C. (2011). Functional extinctions of bird pollinators cause plant declines. Science, 331 (6020), 1019-20 DOI: 10.1126/science.1202389

One of these mutualists is not like the other

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ResearchBlogging.orgOver the last few months I’ve been writing a lot about how different species interactions have different evolutionary effects. The studies I’ve looked at so far focus on effects over just a few generations—barely time to take notice, in evolutionary time. The February issue of The American Naturalist remedies this short-term perspective with a paper showing that over millions of years, two different kinds of mutualists had very different effects on the history of one group of orchids [$a].

The new study examines the evolutionary history of coryciinae orchids, a group of South African orchids that rely on two major groups of mutualists. The first, and perhaps most obvious, are pollinating bees, which coryciinae orchids attract not with nectar but with oils. Like most other orichids, this group of flowers interacts with its pollinators in very specific ways, to the point that different coryciinae species can share a single pollinator by placing pollen on different parts of the pollinator’s body, as seen in the image below.

Double duty: This bee is carrying pollen from one orchid species on its forelegs, and pollen from another orchid species on its abdomen. Photo from Waterman et al (2011), figure 1.

The second important group of mutualists are mycorrhizae, a class of fungus found in soil, which colonize plants’ roots. Mycorrhizae aid their hosts in taking up minerals, particularly phosphorus, in exchange for sugar supplied by the host. In certain kinds of soil, having the right mycorrhizae is the difference between life and death for a plant.

Although both pollinators and mycorrhizae are vital to an orchid’s success, they should contribute to forming new orchid species in very different ways. Evolving a new pollinator relationship can directly create reproductive isolation for a flowering plant, independent of other ecological considerations. On the other hand, mycorrhizae are closely linked to basic ecology, because the mycorrhizae in a plant’s roots determine what kinds of soils it can use—wet or dry, acidic or alkaline. If new orchid species usually form by adapting to new habitats, they probably acquire new mycorrhizae while doing so.

If changing a trait—in this case, a mutualistic relationship—is related to forming new species, then closely related orchid species will be more likely to differ in that trait. This turns out to be the case for pollinators—the more closely related two orchid species are, the more likely they are to use different pollinators, or different parts of the same pollinator. However, the reverse is true for mycorrhizae. The more closely related two orchids are to each other, the more likely they are to have the same mutualistic fungi in their roots. This finding that pollination matters most to species formation is right in keeping with Verne Grant’s classic study noting that animal pollinated plants tend to differ more in their floral structures—the parts that interact with pollinators—than in other traits.

The authors followed up on these results with field experiments on a few selected species, and found that co-occurring orchids could often successfully pollinate each other, if the pollen was deliberately placed. In these cases, differences in specialized pollination interactions are most of what maintains the orchid species as separate genetic entities. On the other hand, closely related orchids that grow in adjacent habitats did just fine when transplanted into each others’ soil—and mycorrhizae.

Biologists studying the effects of pollination on plant species formation have recently become more aware that correlation does not necessarily imply causation. New pollinator interactions certainly might form new species—but it is also possible that new orchid species created by other forces must rapidly evolve new pollinator interactions to compete with existing species.

References

Armbruster, W., & Muchhala, N. (2008). Associations between floral specialization and species diversity: cause, effect, or correlation? Evolutionary Ecology, 23 (1), 159-79 DOI: 10.1007/s10682-008-9259-z

Waterman, R., Bidartondo, M., Stofberg, J., Combs, J., Gebauer, G., Savolainen, V., Barraclough, T., & Pauw, A. (2011). The effects of above- and belowground mutualisms on orchid speciation and coexistence. The American Naturalist, 177 (2) DOI: 10.1086/657955

Scientific American guest blog: Ecological opportunity is all around us

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ResearchBlogging.orgThe latest entry in the wide-ranging Guest Blog at Scientific American is a post by yours truly, about a subject I’ve discussed before:

Since the Origin was first published, biologists have come to use the phrase ecological opportunity to describe the processes that can produce a diverse group of species from a single colonizing ancestor. Islands provide colonizing species with new food resources and an escape from predators and competitors. Under these highly favorable conditions, island species can live at much higher population densities than possible on the mainland—a phenomenon called density compensation. This increase in population size is often accompanied by increased variation among individuals, and greater competition from crowding neighbors creates strong benefits for individuals that try new ways to make a living.

Given enough time, one big, variable population will begin to fracture into smaller populations with different lifestyles. Given even more time, those smaller populations will stop interbreeding, and become different enough to call separate species. If that seems like a stretch of the imagination, consider that the processes of ecological opportunity are occurring all around us—as invasive species spread across the landscape, and viruses multiply in a new victim’s bloodstream.

To learn how ecological opportunity really is all around us, you’ll have to go check out the whole post.

Kudzu, taking advantage of ecological opportunity. Photo by Suzie T.

Reference

Yoder, J.B., S. Des Roches, J.M. Eastman, L. Gentry, W.K.W. Godsoe, T. Hagey, D. Jochimsen, B.P. Oswald, J. Robertson, B.A.J. Sarver, J.J. Schenk, S.F. Spear, & L.J. Harmon. (2010). Ecological opportunity and the origin of adaptive radiations. Journal of Evolutionary Biology, 23, 1581-96 DOI: 10.1111/j.1420-9101.2010.02029.x

Principle interviewee: Erica Bree Rosenblum

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This post was chosen as an Editor's Selection for ResearchBlogging.orgSince her office is just down the hall from mine, I couldn’t very well write about Erica Bree Rosenblum’s latest scientific paper without talking to her about it in person. Rosenblum and her coauthor Luke Harmon weave together the stories of three lizard species’ evolutionary responses to the gypsum dunes of White Sands, New Mexico. As Rosenblum told me in our interview, the study both consummates work she began as a doctoral student and suggests new avenues of study at a striking and beautiful field site.

Erica Bree Rosenblum at White Sands, where she has studied lizards’ adaptation to the dramatic gypsum dunes since graduate school. Photo courtesy Erica Bree Rosenblum.

(I’ve edited the transcribed interview for clarity and length, and paraphrased the questions I asked in person to minimize my interruptions. Rosenblum previewed, corrected, and approved the text of her answers and my questions as they appear below.)

Jeremy B. Yoder: Tell me about the new study and its context.

Erica Bree Rosenblum: Some of the things that are compelling about White Sands that motivated us to write the “Same Same but Different” [$a] are that there are a number of different species that colonized this recent formation. … At first blush, this system looks all “same same.” You look at the main trait that has allowed these animals to survive there, which is becoming light in color, and many diurnal animals at White Sands are white, unless they have some other strategy for avoiding predation. … So a lot of my work over the last several years has been focused on the “same same” aspect of convergent evolution and on the one trait that appears to be the key trait for colonizing, which is light color.

The motivation of this paper was that there is an enormous “but different” side to the story, because there are three lizard species there, and they exhibit some really compelling differences in their degree of adaptation and their progress toward speciation. And also if you start looking at other traits besides color, if you take a multidimensional perspective on adaptation, then there are a lot of really striking differences across species.

JBY: Body size and limb length?

EBR: Body size and limb length and also the genetic basis of color and how structured the populations are across the ecotone. [The transition zone between white sand dunes and dark soil – JBY] So the motivation for this study was to look at what are the essential factors for ecological speciation and then what are the promoting factors for ecological speciation and how might the three species differ.

JBY: How did you start studying the White Sands lizards in the first place?

EBR: I was co-advised in graduate school by two eminent evolutionary biologists who have opposite perspectives on how you find study systems. My first year in graduate school, my one advisor, Craig Moritz, said to pick the theory you are interested in first and then find the system that will let you address that theory. My other advisor, David Wake, said to pick something that you love aesthetically, and then learn more about that. So I had these competing influences, in that sense, when I was trying to form my dissertation project.

Rosenblum and her collaborator Luke Harmon pursue Sceloporus magister, a close evolutionary relative of one species that has colonized White Sands. Photo courtesy Erica Bree Rosenblum.

I had just come back from a bunch of years abroad, and I knew I didn’t want to do research overseas. I also knew that I wanted to do my own thing and just “plug into” a system that had already been established. So I had an idea for wanting to do a study about ecotones—to study divergence with gene flow—in herps. [Lizards and snakes – JBY]

I had talked with different people and taken a map of the U.S. and circled every place that had really sharp transition zones that had to do with interesting problems in herpetology. So I had considered other field sites—in some of the lava flows in California that have strong transition zones, coastal-to-inland [transitions], these cool legless lizards in California—there’s a bunch of strong ecotonal transitions in western U.S. reptiles.

So I circled a bunch of places on the map and I was driving around catching animals and thinking about what I wanted to do. And when I got to White Sands, the Dave Wake part of me was drawn to it aesthetically. … It just seemed like such a striking example of adaptation with such clear possibilities. I knew I wanted to study something simple enough to wrap my head around, and White Sands has a striking, small, depauperate community, so you can actually study everything. And with a few exceptions, no one had done any biological research at White Sands since the forties, when the White Sands species were described.

JBY: What question would you like to have answered five years from now?

EBR: One of the big things I’d like to know is about the dimensionality of selection in the wild. We have a tendency to think about whatever trait seems most accessible to us, but when environments change, organisms are confronted with a lot of adaptive problems to solve at once.

… Number one is understanding the genetic architecture of adaptation and speciation. We know a lot about genotype to phenotype connections in natural populations, but we don’t know a lot about genotype-to-phenotype-to-speciation connections. I’m really interested in traits that might function as “magic traits,” that make speciation easier. I’m interested in whether [for White Sands lizards] color serves as a magic trait and can “high-tail” populations towards speciation.

The other thing I’m interested in is the genetic architecture of multidimensional adaptation. If you have lots of traits that are changing in a new environment, and it is happening very quickly over time, are the genes that underlie those adaptive traits all clustered in the genome? Is there a “signature” of multidimensional adaptation at the genetic level?

And then the third thing is about the predictability of evolution in general. I think it would be really fun to do a more systematic study of the entire fauna at White Sands and understand not just three lizard replicates but all the other species that are white, from invertebrates to mammals, to understand how predictable those adaptive changes are.

Different shades of Sceloporus undulatus, one of the three lizard species adapted to life at White Sands. Photo courtesy Simone Des Roches.

JBY: What about ten years from now?

EBR: The challenge of working at White Sands is that it’s a compelling empirical system to test some classic population genetics ideas, but it’s very hard to develop general conclusions from one system with three replicates. It’s nice to have the three lizard replicates, but it’s still only one system in one place. I’ve tried to visit all the other gypsum sand dune systems in the world. There are others—in Texas, in Mexico … they have unique faunas in other ways, but none of them seem to have blanched species. So when you study natural systems, finding compelling evolutionary replicates can be difficult.

JBY: And when we go looking for study systems we often find the ones with the strongest signals first.

EBR: That’s right … Another example where we’re running into a problem is that … in two of the three species the gene that controls color is the same gene, but has different dominance patterns [PDF]. In one species the mutation that leads to white color is recessive and in the other it’s dominant. And there’s a longstanding debate from Haldane, of how dominance should influence adaptation, but it’s just an N of two. So we could get any pattern. We’re doing follow-up studies to see if the predictions would be upheld in terms of how dominance affects the rate at which adaptive alleles are fixed, and visibility to selection. But whichever way the story goes, it’s either the way you expect it or the way you don’t expect it, but it’s just two replicates. So that is one challenge of studying things in nature.

JBY: Let’s conclude with an outrageous, blog-oriented question: Is White Sands the new Galapagos Islands?

EBR: Yes. [Laughs]

JBY: That’s what I hoped you’d say.

EBR: There are things that are compelling about white sands not only for learning about evolution but also for teaching about evolution. One of the new grants I have is for integrating research and outreach there, because it’s such a compelling place to say, “this is how adaptation happens.” You can see it with your eye, and it’s exactly what you expect. We just finished helping build a new evolution museum at the visitor center at white sands. … So I think that it has cool potential for helping public education around evolution, and it’s not as expensive to go there as it is to go to the Galapagos!

References

Rosenblum, E., Rompler, H., Schoneberg, T., & Hoekstra, H. (2009). Molecular and functional basis of phenotypic convergence in white lizards at White Sands. Proc. Nat. Acad. Sci. USA, 107 (5), 2113-7 DOI: 10.1073/pnas.0911042107

Rosenblum, E., & Harmon, L. (2010). “Same same but different”: Replicated ecological speciation at White Sands. Evolution DOI: 10.1111/j.1558-5646.2010.01190.x

For lizards on white sands, evolution doesn’t quite repeat itself, but it does rhyme

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ResearchBlogging.orgSee also my interview with Erica Bree Rosenblum, the lead author of the study discussed here.

If life on Earth started over from scratch, would it eventually re-evolve the world we see today? This is the kind of question that makes for an entertaining argument over beers: “Well, without the Chicxulub impact, the dinosaurs wouldn’t have gotten out of the way for mammals.” “But dinosaurs were already turning into birds!” You might think that to resolve that argument, we’d need a second Earth and four billion years of research funding. And maybe we would, to resolve it conclusively. But sometimes nature performs a small-scale version of that kind of experiment for us.

The gypsum sand dunes of White Sands, New Mexico. Photo by Fabian A.M.

One such natural experiment is at a special site in the New Mexico desert, a patch of gypsum sand dunes called White Sands. As my University of Idaho colleagues Erica Bree Rosenblum and Luke Harmon show in a paper just released online ahead of print by the journal Evolution, three species of lizards that colonized White Sands are following the same evolutionary path, but in different ways and at different paces [$a]. In the words of a Thai expression Rosenblum and Harmon choose to describe their thesis, the three lizards are “same same but different.”

Continue reading →

Is dilution the solution to information pollution?

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ResearchBlogging.orgChris Smith, my good friend and longtime collaborator on all things relating to Joshua trees, pulled into the gas station well after dark. He was on his way back to our field site in the Nevada desert, and this was the last stop before cell phone signals disappeared for good and you had watch the highway ahead for free-range cattle.

It was also the last stop for fresh water, gasoline, and propane. Chris fueled up the van, then went inside for help refilling the spare propane tank. The unshaven, sun-darkened night clerk gave Chris’s flip-flops and tee shirt a sidelong look—they might’ve been perfect back in Vegas around midday, but now it was a freezing high desert night. Clearly unpleased to have to go outside himself, the clerk zipped up his parka and followed Chris out to fill up the tank.

Why do scorpions fluoresce under UV light, anyway? Photo by Furryscaly.

Refilling the propane tank entailed much adjusting of valves and connecting of pipes, which the clerk accomplished with a large wrench. Somewhere a valve misconnected to a pipe, and Chris’s jeans were suddenly soaked in liquid propane. The clerk swore elaborately at the valve, blamed the lazy bastards on the day shift, and took out his frustration on the propane tank with the wrench.

When this miraculously failed to engulf the two of them in fiery death, the clerk straightened out the connection and started filling the spare tank, then turned to Chris and said, “So what’re you doing out here, anyway?”

Evolutionary biologists learn to be vague about their profession in rural areas, so Chris said he was a biologist. No, he wasn’t working for the Air Force base over at Groom Lake. He was studying Joshua trees.

“You must know something about evolution, right?” said the clerk. “I’ve got a question for you.”

Oh, brother, thought Chris. Here we go. How long till this tank fills up?

“You know how scorpions glow under ultraviolet light,” they clerk asked.

Why yes, I do, said Chris.

“How come? I mean, what possible adaptive value does that have?”

Well, you know, said Chris, I don’t have any idea.

“I hear,” said the clerk, “that fossil scorpions millions of years old will glow if you shine a UV light on them. That’s pretty wild, isn’t it?”

You’re right, said Chris. That’s pretty wild.

Chris told this story to everyone else in the field team as soon as he got back to camp, and I think it’s a great illustration of two points that inform the way I think about science blogging. First, that scientists are maybe a bit quick to assume hostility in their audience; and second, that telling cool stories about the natural world is at least as important as confronting the hostility really is out there.

I’ve been thinking about these points ever since ScienceOnline 2011, which I finished with the “Defending Science Online” session, a discussion of strategies for countering all manner of anti-scientific bunk: climate change denialism, opposition to vaccination, creationism, homeopathy. The panelists discussed specific events and general strategies, but they really only discussed confrontation. I left with the nagging feeling that identifying and refuting non-science, however well it’s done, isn’t enough.

Scientific misinformation needs to be contained, but it also needs to be diluted. Photo by kk+.

The trouble with refutation is that once creationists or anti-vaxxers piss in the information pool, it’s nearly impossible to clean up the water. A widely-cited recent study of fact-checking in news articles has shown that corrections often fail to reach people who don’t want to hear them—and the act of correcting a misperception can actually reinforce it [PDF]. Other works shows that even when you convince people that the information they cite in support of political positions is wrong, they hold on to those positions [PDF].

When real-world pollution can’t be extracted from the environment, there’s one final line of attack: dilute it. In the sense that what we call pollution is often a dangerous artificial concentration of some substance that is non-dangerous at much lower, natural levels—carbon dioxide, for instance—the solution to pollution is, indeed, dilution. In the case of information pollution, which we can’t really prevent or contain, we can dilute non-science with, yes, science.

In other words, the best weapon against denialism may not be explicit takedowns of denialism, but good, clear, accessible discussion of science and all the ways it’s awesome. I can speak to this from my own experience growing up in a neutral-on-evolution household in the midst of quite a lot of creationists. I can’t recall that I ever decided evolution was a historical fact because of something I read against creationism. Instead, I came to accept the fact of evolution because I read and watched and listened to a lot of popular science—National Geographic, Ranger Rick, and Nature on PBS—that just took evolution as a given, and showed how it explained the world.

So, while folks like PZ Meyers, NCSE, and Ben Goldacre fight the good fight, I think we shouldn’t forget the value of celebrating science without making it a confrontation. And in the era of Science Online, we’re surrounded by people pointing out things as cool as glow-in-the-dark scorpions. See Scicurious’s Friday Weird science posts, Carl Zimmer’s tale of Vladimir Nabokov’s contributions to entomology, Olivia Judson explaining brood parasitism, or Radiolab’s mind-blowing meditation on stochasticity for just a few great examples selected off the top of my head.

This kind of science communication focuses on the grandeur and fun of the scientific view of life, and it wins supporters to science one story at a time. That’s not necessarily the most exciting part of the struggle against ignorance and denialism. But every time we get someone to say, “That’s pretty wild,” we’re making progress.

References

Bullock, J. (2006). Partisanship and the enduring effects of false political information. Presented at the annual meeting of the Midwest Political Science Association. PDF.

Nyhan, B., & Reifler, J. (2010). When corrections fail: The persistence of political misperceptions. Political Behavior, 32 (2), 303-30 DOI: 10.1007/s11109-010-9112-2

Communities within communes: Do bees’ social lives influence their gut bacteria?

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ResearchBlogging.orgAs anyone who’s trying to sell you probiotic yogurt will tell you, what you can eat often depends on what’s living in your gut. For many animals, symbiotic bacterial communities help break down foods that would otherwise be indigestible. Perhaps most famously, termites would be unable to eat wood without specialized microbes in their guts [$a], but many other animals host bacteria that break down cellulose, the tough structural sugar of plant tissue, or to supply nutrients lacking in their diet.

This honeybee is carrying more than pollen. Photo by Danny Perez Photography.

The importance of gut microbes for digesting certain kinds of food has led to the suggestion that acquiring the right microbes can be an evolutionary key innovation—a change that creates access to new resources and spurs adaptive radiation. A 2009 study of gut microbes in ants found that evolutionary transitions to eating plants were associated with acquiring similar gut microbes.

So what about the biggest group of herbivorous hymenoptera, the bees? Bees’ ancestors were most likely predatory wasps, but some time in the Cretaceous Period they began making a living on pollen and nectar instead. A new study of gut microbes in a wide diversity of bees suggests that social organization, not diet, changed what lives inside bees’ bellies [$a].

The study examined the bacteria inside representatives of seven bee families, collecting sequence data from a gene widely used in studies of bacteria. The method employed allowed the authors to identify not just what kinds of bacteria were present, but how abundant each kind was. This microbial profile was specifically compared to the profile for Apis mellifera, the honeybee, whose gut microbes have been studied quite a bit already.

The bees form a monophyletic group—they all share a single common ancestor—and they are overwhelmingly herbivorous. Phylogenetic logic suggests, then, that any changes to the gut microbe community associated with the evolutionary transition to eating pollen and nectar would have occurred once, in the common ancestor. The microbes that facilitated that transition should also be widely shared by herbivorous bees.

In fact, most of the bee families sampled had little in common with the honeybees’ gut bacteria. Close relatives of the bacterial types found in Apis mellifera only turned up in two other Apis species, and bumble bees (genus Bombus). Since herbivory doesn’t explain this pattern of similarity (or lack thereof), the authors suggest that what really matters to bees’ guts is social behavior. Apis and Bombus are eusocial, forming hives of related workers cooperating to support a handful of reproductive individuals; the other bees surveyed in the study live mostly alone.

Life is different in the hive. Photo by stewickie.

As the authors note, eusociality would certainly change the environment offered to symbiotic bacteria. Bees in a hive should transmit bacteria among themselves, especially when feeding larvae. So eusocial bees mostly get their gut bacteria from their sisters. The bacteria in the guts of the solitary bees surveyed were mostly related to strains found in soil and on plants—so solitary bees are probably populating their guts with bacteria from their environment.

The idea that eusociality has shaped bees’ interactions with their symbiotic bacteria is interesting, but the data presented in this study are preliminary at best. The sampling of bee diversity presented here is broad, but not very deep—most of the bee families covered are represented by only one or two species. Understanding the effects of social structure on bees’ gut bacteria will take much finer-grained sampling to focus on evolutionary transitions not from predation to herbivory, but from solitary to eusocial lifestyles.

References

Kaltenpoth, M. (2011). Honeybees and bumblebees share similar bacterial symbionts. Molecular Ecology, 20 (3), 439-40 DOI: 10.1111/j.1365-294X.2010.04960.x

Martinson, V. G., B. N. Danforth, R. L. Minckley, O. Rueppell, S. Tingek, & N. A. Moran. (2011). A simple and distinctive microbiota associated with honey bees and bumble bees Molecular Ecology, 20 (3), 619-28 DOI: 10.1111/j.1365-294X.2010.04959.x

Ikeda-Ohtsubo, W., & A. Brune (2009). Cospeciation of termite gut flagellates and their bacterial endosymbionts: Trichonympha species and ‘Candidatus Endomicrobium trichonymphae’. Molecular Ecology, 18 (2), 332-42 DOI: 10.1111/j.1365-294X.2008.04029.x

Russell, J., Moreau, C., Goldman-Huertas, B., Fujiwara, M., Lohman, D., & Pierce, N. (2009). Bacterial gut symbionts are tightly linked with the evolution of herbivory in ants. Proc. Nat. Acad. Sci. USA, 106 (50), 21236-41 DOI: 10.1073/pnas.0907926106

Writerly scientist derided scientist-writer?

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ResearchBlogging.orgFollowing up on the recent discovery that novelist and lepidopterist Vladimir Nabokov correctly supposed that Polyommatus blue butterflies colonized the New World in stages, Jessica Palmer points out that none other than Stephen Jay Gould dismissed Nabokov’s scientific work as not up to the same standards of genius exhibited in his novels. She suggests that Nabokov’s work may have been dismissed by his contemporaries because his scientific papers were a little too colorfully written.

Roger Vila, one of Pierce’s co-authors, suggests that Nabokov’s prose style (Wellsian time machine!) did his hypothesis no favors:

The literary quality of his scientific writing, Vila says, may have led to his ideas being overlooked. “The way he explained it, using such poetry — I think this is the reason that it was not taken seriously by scientists,” Vila says. “They thought it was not ‘hard science,’ let’s say. I think this is the reason that this hypothesis has been waiting for such a long time for somebody to vindicate it.”

That’s a little harsh toward scientists, but it seems plausible: creativity in scientific writing is rarely rewarded.

Hyperlink to quoted source sic.

Palmer’s analysis is thoughtful and thorough, and you should read all of it. But she misses what (to me) seems like the best wrinkle in the whole business: Gould, alone of all the scientists, should have been sympathetic to the dangers of writing “too well” in a scientific context.

Stephen Jay Gould, one suspects, never murdered a single darling in a decades-long career of writing for scientific and popular venues. The iconoclastic 1979 paper “The spandrels of San Marco and the Panglossian paradigm: a critique of the adaptationist programme” [PDF], coauthored with Richard Lewontin, is a case in point. Gould and Lewontin wanted to make the point that not all traits and behaviors of living species are necessarily adaptive—that is, evolved to perform a function that enhances survival and/or reproductive success. Today it is widely agreed that this point needed making. But Gould’s writing undercut the success of his own argument, or at least gave his detractors a toehold for derision.

The Cathedral of San Marco in Venice, its structurally practical arches encrusted with Baroque decoration. A metaphor for Gould’s metaphors? Photo by MorBCN.

Gould and Lewontin developed their argument with references to architecture and to literature. They compared non-adaptive traits to mosaics decorating the spandrels of the Cathedral of San Marco in Venice. Spandrels being spaces created between arches, anything decorating them is clearly secondary to the architectural decision to build an arch. They also compared “adaptationist” biologists to the character of Dr. Pangloss in Voltaire’s satire Candide, who claims that “all is for the best in this best of all possible worlds.”

Pangloss is a fool, and biologists who felt Gould and Lewontin were critiquing them took the obvious inference. One of the most biting responses to “Spandrels” focused much more on the style than the substance of the paper. The author, David Queller, titled it “The spaniels of St. Marx and the Panglossian paradox: A critique of a rhetorical programme” [PDF], and the parody only continues from there.

Queller built an elaborate and unflattering image of Gould and Lewontin as Marxists focused on their political perspective like the dog in the old RCA ads fixated on a grammophone. He even referenced one of Gould’s favorite cultural touchstones, the works of Gilbert and Sullivan, to tweak Gould as “the very model of a science intellectual.” Queller manages to have his cake and decry it, too—he mocks Gould and Lewontin with overflown metaphors, then backs off to say that such tactics are irresponsible:

So, how did I like my test drive in the supercharged rhetoric-mobile? It’s certainly been fun … but it’s pretty hard to keep the damned thing on the road. … my little parody of Gilbert and Sullivan’s modern Major General, who knows about everything but matters military, might induce an uninformed reader to conclude that Gould knows about everything but matters biological. But this is exactly the complaint that many biologists would level at Spandrels—that colorful language can mislead as well as inform.

So if Gould’s reading of Nabokov’s scientific achievement was predicated on the opinions of Nabokov’s colleagues, who didn’t care for elaborate prose in their scientific journals, well, I think that’s what my English teachers called irony.

References

Gould, S., & Lewontin, R. (1979). The spandrels of San Marco and the Panglossian paradigm: A critique of the adaptationist programme. Proc. Royal Soc. B, 205 (1161), 581-98 DOI: 10.1098/rspb.1979.0086

Queller, D. (1995). The spaniels of St. Marx and the Panglossian paradox: A critique of a rhetorical programme. The Quarterly Review of Biology, 70 (4), 485-9 DOI: 10.1086/419174

Vila, R., Bell, C., Macniven, R., Goldman-Huertas, B., Ree, R., Marshall, C., Balint, Z., Johnson, K., Benyamini, D., & Pierce, N. (2011). Phylogeny and palaeoecology of Polyommatus blue butterflies show Beringia was a climate-regulated gateway to the New World. Proceedings of the Royal Society B: Biological Sciences DOI: 10.1098/rspb.2010.2213

Finding the middle road: Flowers evolve to work with multiple pollinators

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ResearchBlogging.org

“I’ve had a lot of jobs in my life: boxer, mascot, astronaut, baby proofer, imitation Krusty, truck driver, hippie, plow driver, food critic, conceptual artist, grease salesman, carny, mayor, grifter, body guard for the mayor, country western manager, garbage commissioner, mountain climber, farmer, inventor, Smithers, Poochie, celebrity assistant, power plant worker, fortune cookie writer, beer baron, Kwik-E-Mart clerk, homophobe, and missionary, but protecting people, that gives me the best feeling of all.”
—Homer Simpson

In twenty-two seasons of The Simpsons, the eponymous family’s bumbling father Homer has tried his hand at dozens of different jobs, and failed hilariously at most of them. Homer is a one-man illustration of “Jack of all trades, master of none,” the idea that it’s hard to do many different things well. This principle applies more broadly than the curriculum vitae; in biology, it means that living things face trade-offs between different ways of making a living.


A wild radish (Raphanus raphaistrum) flower. Photo by Valter Jacinto.

For instance, a plant whose pollen is carried from flower to flower by just one pollinating animal only needs to match that one pollinator very well. But most plants’ flowers are visited by many different potential pollinators, and matching all of them probably means finding a middle ground among the best ways to match each individual pollinator. A study of one such “generalist” flower, the wild radish, has found exactly this: working with multiple partners takes evolutionary compromise [$a].

Wild radishes are visited by a wide variety of different insects, including honeybees, bumblebees, syrphid flies, and cabbage butterflies, among others. Each of these pollinators comes to a radish flower with a slightly different agenda. Butterflies are there for nectar, but bees like to eat pollen as well—and bumblebees will sometimes bite into the base of a flower and “steal” nectar without ever coming into contact with pollen. Figuring out how natural selection from each of these different pollinators adds up required some clever experimental design.

The study’s authors arrayed potted radish flowers inside a big mesh flight cage, and then introduced either bumblebees, honeybees, cabbage butterflies, or all three pollinators to visit the plants and circulate pollen from flower to flower. They measured the plants’ flowers before putting them in the flight cage, then let the pollinators do their thing. Afterward, the authors collected seeds resulting from the pollinators’ activity, grew them up, and measured the offspring to see whether their traits differed. The procedure was essentially one generation of experimental evolution.


A cabbage white butterfly (Pieris rapae), one of many pollinator species exerting natural selection on wild radishes. Photo by ComputerHotline.

By taking DNA fingerprints of both the parents and the offspring, the authors could also estimate the relationship between each parental plant’s floral measurements and the number of offspring it produced, either from its own seeds or by pollinating another plant.

The results are complex. Depending on the floral measurement under consideration, different pollinators selected in different directions, or the same direction, or not at all. One particularly interesting result, though, was in the effects each pollinator had on the “dimorphism” of the radish flowers’ stamens—the difference between the length of the shortest, and longest, of the male parts of the flower. Flowers only visited by honeybees evolved less dimorphic stamens, while flowers visited by either bumblebees or cabbage butterflies evolved more dimorphic stamens. Flowers in the treatment visited by all three pollinators, however, evolved to find a happy medium, an evolutionary compromise to work with the different partners.

The way these interactions played out in a flight cage probably don’t reflect exactly how they operate in the wild, but this is a pretty cool result all the same. I’ve written in the past about how incorporating multiple interactions can alter the way coevolution works. Gerbils under attack by fleas are less careful about watching for predators; but for the protists living inside pitcher plants, competitors can help distract predators. Here we have an example of multiple similar interactions pulling a generalized plant in different evolutionary directions.

Reference

Sahli, H., & Conner, J. (2011). Testing for conflicting and non-additive selection: Floral adaptation to multiple pollinators through male and female fitness. Evolution DOI: 10.1111/j.1558-5646.2011.01229.x

Evolution’s Rainbow, from sparrows’ stripes to lizard lesbianism

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This post was chosen as an Editor's Selection for ResearchBlogging.orgEvolutionary biology is not just the study of how living things change over time, but the study of how the diversity of living things changes over time. Diversity is the raw material sculpted by natural selection, carved into more-or-less discrete chunks by speciation, and lost forever in extinction.

Joan Roughgarden is even more preoccupied with diversity than most evolutionary biologists. Some of her earliest published studies examine the evolution of optimum niche width, the range of resources a species uses, using mathematical modeling [$a] and empirical studies of resource and habitat use in Anolis lizards [$a]. Roughgarden didn’t treat a species as a uniform group, but a collection of individuals all making a living in slightly different ways. Among other subjects, her work informed thinking about ecological release, the changes that reshape populations freed from predators or competitors.

White-throated sparrows are just one species with more than two gender roles. (Flickr: hjhipster)

This interest in the evolutionary context of diversity would eventually become much more personal. In 1998, she came out as transgendered, taking the name Joan after decades spent establishing her scientific reputation under the name she was given at birth, Jonathan. In addition to the challenges inherent to gender transition, Roughgarden’s expertise intersects with her identity in one awkward question: in a biological world shaped by natural selection, how can we explain the evolution of lesbians, gay men, and transgendered people—individuals who are not interested in sexual activity that passes on their genes?

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