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

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.”

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Happy Darwin Day!

The co-discoverer of natural selection and author of The Origin of Species was born 202 years ago today. Nerdy festivities are in the offing everywhere, even Moscow, Idaho.

To assist in your festivities, allow me to suggest my postings for Darwin’s 200th (I’m not so down with the Christianity these days, but I still stand by the points made) and the New York Times‘s great annotated copy of the Origin. You could also check out this interview with evolutionary biologist David Rezick, who has written his own annotated version of The Origin.

Charles Darwin, born 12 February, 1809. Image via Pharyngula.
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Science online, bright and beautiful edition

Beep-beep. Photo by jafro77.

So, um … have you “liked” Denim and Tweed on Facebook yet? I’m sure you meant to. I bet you were just busy with other stuff, earlier.

  • Run, run, as fast as you can … For small ground birds like ptarmigans, the energetic cost of running decreases as they go faster.
  • Declining effect. Ecologists really shouldn’t be all that surprised, or worried, about the “decline effect”.
  • Skin guns don’t heal people. Doctors with skin guns heal people. A new “skin gun” can heal second-degree burns by spraying them with stem cells.
  • Microscopic foraminifera know more than you might think. The history of a warming Northwest Passage is encoded in plankton.
  • Ants are total mutualism sluts. Microbes living on leafcutter ants generate antibiotics that may help fight bacterial infections of the ants’ fungus gardens.
  • Harder than it sounds. Science educators need to know when, and how, to say, “I don’t know.”
  • Is that a just-so story in your pocket, or are you just happy to see me? Scicurious and A Primate of Modern Aspect consider adaptive explanations for the shape of the human penis.

Video this week, via Thoughts from Kansas: a Sunday School song for the combative biologist. (See also Eric Idle’s classic “All Things Dull and Ugly”.)

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Is dilution the solution to information pollution?

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

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If you like D&T, you can now “like” D&T

In another round of neurotic revisionism, I’m taking Denim and Tweed to full Facebook. That means this blog now has a Facebook fan page, and a new widget placed prominently in the sidebar. This makes three box-of-faces widgets in the D&T sidebar, and that’s frankly too many. So I’ll be phasing out both the Blogger and NetworkedBlogs boxes in about a month from today. (You can still follow D&T through those systems, your followership just won’t be recorded in the sidebar.) Sorry! My aim is to make this the last such rejiggering for the long term.

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Science online, light fantastic edition

  • The poetic possibilities alone are staggering. Given a wing with the right optical properties, it’s possible to fly on a beam of light.
  • Which is why I buy in bulk. Serving snacks in smaller packages can help people eat less—but it only works for overweight people.
  • “Digital rectal stimulation.” Really. Science finds a cure for intractable hiccups.
  • Being female ≠ being anemic. Normal blood loss during menstruation does not cause iron deficiency.
  • Two million years of eating bamboo. Although fossils of the giant panda’s ancestors are few and far between, paleontologists are beginning to piece together their evolutionary history.
  • Context! Ed Yong compiles five years of stem cell research into an interactive timeline.
  • Boy, is my face red. How did blushing evolve as an involuntary social signal?

And now, Nature Video explains a new study [$a] that suggests why seahorses are horse-shaped. Via The Hairpin.

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

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

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Carnival of Evolution No. 32

Correction, 11:25h: I’ve just been informed that the fish in the photograph below are not swordtails, but guppies. Burned again by Flickr taxonomy! The real Darwin would’ve got it right, I’m sure.

The Carnival of Evolution is a monthly collection of online writing about evolutionary biology and its cultural and political implications, hosted by a different blogger every month. Today, Denim and Tweed hosts CoE for the first time. Since Charles Darwin’s birthday is this month (only 12 shopping days left!), I thought it might be appropriate to imagine what Darwin himself might have to say about this month’s posts. Share and enjoy!

Photo via WikiMedia Commons.

Down. Bromley. Kent.
Febr. 1, 2011

My dear Hooker,

I was grateful for your very kind wishes; and for the book about the Anoles of the West Indes, which I expect I shall read with much enjoyment. The merest thought of an approaching 202nd birthday makes me feel the need for another trip to Malvern; but I do find some relief in my reading, of which I must needs do more every day it seems, only to keep abreast of the latest work. My great-grandson presented me last month with an i-Pad, a charming device; I can now consult the “web-logs” in the garden, when it is pleasant.

And there is such a lot of reading to do! It seems I read constantly about work extending the ideas I first proposed more than 150 years ago; it is gratifying, and rather humbling, to see what has grown from my little “abstract.” And dear old Wallace’s, of course. (Have you heard from Wallace recently? The last I knew of him, he was departing on that expedition with Greenpeace; but that was more than a year ago.)

Once I suspected my thoughts upon the origins of species would soon be only of interest to students of history and philosophy, but every-where I look I find someone else building upon my ideas.

For instance, experimentation has recently shown that more diverse communities of microbes use resources with greater efficiency, which extends my own simple trials with grasses on a small plot of ground. I am quite interested in the ongoing study of such interactions between species; there has been much interesting work on the co-evolution of hosts and their beneficial symbiotes, in which it is debated whether hosts may control their symbiotes without the need of punishments. And I recently saw that some species of citrus can attract parasitic worms to drive off weevil larvae.

I was also charmed to discover that butterflies of the species Eurybia lycisca, have evolved elaborately long tongues, long enough to take nectar without pollinizing; an unfortunate development for the flowers they visit! And I have recently seen a delightful study of the leaping of Blenniid fishes, supported by many moving pictures; and the very interesting findings of separated forms of the Clouded Leopard in Borneo and Sumatra.

(Here is a charming moving picture of the Clouded Leopard. What a blessing You-Tube is for the stay-at-home naturalist!)

Which is not to say that I think all developments from my theories are sound; you may have read about the idea that women’s tears are modified to save them from molestation, which seems to me curious indeed. I have also seen some very odd speculations upon the morphology of human beings in the distant future. I do not understand why the form should be arboreal. It may be worth recalling, in this context, that Humankind is only one twig in the evolutionary tree of the Apes.

Still more interesting to me is discovering the ways in which I was mistaken (embarrassing as they often are) and facts I was unable to percieve at the time of first writing. For instance, this extensive essay about Mosaic Evolution, or what I might call the Independent Modification of Parts; which evidently has its roots in Lamarckism. We may have been too harsh on the good Chevalier. Equally as interesting is this disquisition upon conditions in which Natural Selection may not lead to modification of descendants. Of course a lack of adaptation might be just as informative as the process of adaptative modification itself!

Of course the experiments of Gregor Mendel were an important improvement to what little understanding I mustered in The Origin; some suggest that now that Mendel’s thinking is over-simple, but it retains much power I feel. The study of living species is so very complicated! We must keep watch not only upon D.N.A. but the myriad complications of its translation to form the structures of the body, and even the duplication of genic code to originate new structures. The greater understanding we have gained since I first concieved of Natural Selection promises to continue improving the condition of humanity; I read, for example, that we may manipulate adaptations lengthen life at a cost to fecundity in order to breed more productive crops.

I must admit that I badly underestimated the role of chance and mutation in the descent of species; especially the degree to which it could allow imperfection to persist, even costly mis-folding of protein molecules. And yet chance changes may have profound consequences for the future of a species, much as my lucky chance to join the crew of the Beagle started me as a naturalist.


A pair of sword-tails guppies. Photo by Alice Chaos.

I have read recently also of several challenges to my original thoughts on Selection in Relation to Sex; experimentation has found, for example that the sexual ornaments of Xiphophorus sword-tailed fishes, do not hamper the males’ abilities to escape danger, which suggests they carry no great cost.

And of course it seems that there have always been persons who object to the idea that we might share kinship with apes and even sessile cirripedes; but fortuitously they seem not to have come up with any particularly novel arguments since 1859. And we may even use Natural Selection to explain the religions that deny the common descent; I suspect that social influences are greatly to blame.

With learned discussion so abundant and easy to find, it is truly a wonder that ignorance and misinformation persist; if only more people did their researches with proper care!

Yours very sincerely,

Thanks to everyone who contributed to this month’s Carnival! Want to submit posts for next month? Go to the BlogCarnivals form, or check out the list of past and future hosts at the carnival index page. Just as importantly, the Carnival needs hosts starting next month! If you’d like to host the Carnival, CoE overlord Bjørn Østman wants you to e-mail him right now.

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