Is this a thing yet? The rise of the MOTHs

Benedict Cumberbatch as Peter Guillam in Tinker Tailor Soldier Spy. (Dear Film)

I finally got around to seeing the new adaptation of John Le Carré’s Tinker, Tailor, Soldier, Spy this weekend, and, wow. It is everything I want in a spy movie: Beautifully visualized, relentlessly realistic, complex, and excellently performed by basically every worthwhile British-accented male actor alive today—Gary Oldman’s subtle turn as the master spy George Smiley is entirely Oscar-worthy, and Benedict Cumberbatch is excellent as Peter Guillam, the Watson to Smiley’s Holmes (an insidery irony, as TV Tropes points out).

But one detail of Tinker Tailor got me thinking about something beyond the murky world of Cold War spycraft: in a brief but touching twist, Guillam is forced by circumstances to abandon a male lover, lest he be outed and fired. Guillam’s sexuality is given no prior indication beyond his predilection for slightly flashier ties than those preferred by his colleagues in British Intelligence. It’s in line with the plot, and a nice bit of added depth to a great performance by Cumberbatch—yet I’ve seen it before. Several times before, in fact.

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Happy Darwin Day!

Charles Darwin. Image included under Fair Use rationale.

Charles Darwin, who first proposed that natural selection could be responsible for “descent with modification,” the observation (which predates Darwin) that living species change over time and give rise to new species, was born on this day in 1809.

By all accounts, Darwin was a geek’s geek—uncomfortable in high-pressure social situations and devoted to the fiddly details of his scientific work. But he also seems to have been a quietly friendly chap, keeping up a tremendous volume of correspondence with other scientists all over the world, and, most charmingly, bringing his children into the fun of puzzle-solving that lies at the heart of science.

I don’t know of better proof of this than this account of Darwin’s familial experimentation, produced for NPR by Robert Krulwich with writer David Quamman, a couple years back around the Darwin Bicentary. (Thanks to Madhusudan Katti for reminding me about it!)


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Science online, gonorrhea, drugs, and bison edition

Bison. Photo by USFWS Mountain Prairie.

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Nothing in Biology Makes Sense: Making sense of ubiquitous plant defenses

A giraffe, dodging thorns like a pro. Photo by Colin Beale, via Nothing in Biology Makes Sense.

We have a second post at the collaborative blog Nothing in Biology Makes Sense! this week, in which ecologist Colin Beale (guest posting from Safari Ecology) tackles the question of why so many African savannah plants grow thorns:

At one level the answer is obvious—there are an awful lot of animals that like to eat bushes and trees in the savanna. Any tree that wants to avoid this would probably be well advised to grow thorns or have some other type of defence mechanism to protect itself. But then again, perhaps the answer isn’t so obvious: all those animals that like to eat bushes seem to be eating the bushes perfectly happily despite the thorns. So why bother having thorns in the first place?

To find out why, and see more of Colin’s great photos, go read the whole thing. ◼

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Nothing in Biology Makes Sense: Making sense of inbreeding depression

Bighorn sheep. Photo by Noah Reid, via Nothing in Biology Makes Sense.

This week at the collaborative blog Nothing in Biology Makes Sense!, Noah Reid returns to discuss the bane of small, isolated populations: inbreeding depression:

Iconic North American species such as grizzly bears, red-cockaded woodpeckers, and the American burying beetle today inhabit only small fractions of the ranges they occupied only 100 years ago. A result of this fragmentation is that many individuals exist in small, isolated populations. In these populations, a curious phenomenon often emerges, one that can only be understood in light of some basic evolutionary theory.

To find out more about that phenomenon, and when it can become hazardous to a population’s health, go read the whole thing. ◼

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Color indicates poison in “poison dart” frogs—honestly!

A strawberry poison dart frog; apparently the San Cristobal color morph. Photo by Wilfredo Falcón.

ResearchBlogging.orgAlmost everyone knows the basic story behind the brilliant coloring of poison dart frogs. These tiny tropical rainforest amphibians secrete toxic alkaloids from their skin, and their bright colors are aposematic signals to warn away potential predators.

You’d expect species that are all sending the same message—Poison! Don’t eat!—to use the same signal to do it. Local studies confirm that birds are more likely to attack poison dart frogs who look different from other poison dart frogs in a given area. Yet not all poison dart frogs have the same color pattern, or even similar color patterns. Far from it—frogs within the same species can look completely different.

One possible explanation is that frogs with different coloration are not, in fact, sending the same signal. Brighter color could indicate greater toxicity. That seems to be the case for one highly variable species, the strawberry poison dart frog Dendrobates pumilio. A paper just published as an online, open-access article in The American Naturalist demonstrates that D. pumilio‘s colors are “honest signals”—and those signals are directed at specific predators.

The many colors of Dendrobates pumilio. Figure 1 from Maan & Cummings (2012).

The new study’s authors, Martine Maan and Molly Cummings, selected a study species that is a veritable rainbow of aposemitism, as you can see from the excerpted figure above. Different populations of Dendrobates pumilio are orange, red, green, blue, and yellow, with or without black spots. Maan and Cummings make sense of that colorful diversity in two major ways: first, by finding out whether there’s a relationship between color and poison, and second, by making an educated guess about how the different color morphs look to D. pumilio‘s many predators.

For the first part, Maan and Cummings took an objective measure of color—reflectance spectrum of frogs’ skin, measured under standardized lighting—and compared it to an objective measure of toxicity—how much discomfort mice exhibited from an injection of frog skin extract. (The mouse injection method is apparently a standard toxicity assay, and I guess it makes sense if you don’t know the specific chemicals that make the frogs poisonous.) The coauthors found a strong relationship between skin brightness and toxicity—frogs with brighter coloring were more poisonous.

Objectively bright coloring isn’t quite the same thing as looking bright to a predator, though. Different animals have different color vision—a frog that looks brightly colored to a frog-eating bird might not be particularly showy to a frog-eating snake, because birds and snakes have different suites of sensory cells in their eyes. So the coauthors then fed the spectral readings from the frogs into mathematical models that estimate how the frogs look to different kinds of animal vision. (This approach has been used elsewhere—for instance, to determine how well brood-parasitic cuckoo eggs blend in with their hosts’.) Maan and Cummings applied models based on the visual sensitivity of crabs, snakes, two kinds of bird vision, and frog vision.

Another strawberry poison dart frog, this time the color morph found on Aguacate. Photo by Drriss.

They found strong relationships between the frogs’ toxicity and their colors as seen by birds, and as seen by other frogs. The crab vision model varied depending on what kind of material the frog would be viewed against—to a crab, the frogs were conspicuous against bark or leaf litter, but not against green leaves. Meanwhile, the snake vision model didn’t perceive any particular relationship between brightness and toxicity. Those results make a lot of sense. Birds are most likely to spot prey from a distance, and make a decision to pursue it or not without getting up close. Crabs aren’t likely to encounter frogs up in the foliage, but on the ground, in the leaf litter. And snakes are less likely to rely sight than on chemical senses—taste or olfaction—in evaluating a potential meal.

This study doesn’t directly demonstrate the action of natural selection, and that leaves a significant question hanging: Why should Dendrobates pumilio signal its toxicity honestly? Certainly, if you’re a highly toxic frog, you’d want to let predators know; but if you’re less toxic than the frogs in the next population, why would you tell the world? Indeed, other species of poison dart frogs have evolved mimicry—bright colors without poison.

That suggests the honest coloration within D. pumilio is be due to more than just selection by predators. Perhaps coloration serves social functions, and then more conspicuous color morphs need to be more toxic to fend off more frequent predator attacks. Or there may be genetic constraints that link bright color and toxicity within the species, and both have evolved local differences due to genetic drift. Finding out how selection and other evolutionary forces have created this pattern would be no small project, but I think it’ll make an interesting story in the end. ◼

References

Darst, C. (2006). A mechanism for diversity in warning signals: Conspicuousness versus toxicity in poison frogs Proc. Nat. Acad. Sciences USA, 103 (15), 5852-7 DOI: 10.1073/pnas.0600625103

Maan, M., & Cummings, M. (2012). Poison frog colors are honest signals of toxicity, particularly for bird predators. The American Naturalist, 179 (1) DOI: 10.1086/663197

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Apprently, they don’t

Minnesota Republicans, the state party that gave us Michele Bachmann, covered themselves in Santorum.

Meanwhile, my precinct caucus for the Democratic Farm Labor party overwhelmingly elected to support Barack Obama for President. That’s, er, 25 for and 1 “uncommitted.” Needless to say, when you’ve got an incumbent, interest isn’t going to be very high. ◼

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Proposition 8 overturned

… by the California Supreme Court the Federal Ninth Circuit Court of Appeals. Proposition 8, of course, was a ballot initiative that amended the California state constitution to forbid state recognition of same-sex marriages, passed in 2008 after the state Supreme Court legalized same-sex marriage, and thousands of couples had become married.

From the text of the decision, which is a model of sharp language:

All that Proposition 8 accomplished was to take away from same-sex couples the right to be granted marriage licenses and thus legally to use the designation of ‘marriage,’ which symbolizes state legitimization and societal recognition of their committed relationships. Proposition 8 serves no purpose, and has no effect, other than to lessen the status and human dignity of gays and lesbians in California, and to officially reclassify their relationships and families as inferior to those of opposite-sex couples. The Constitution simply does not allow for “laws of this sort.” [Emphasis added.]

The logic of the decision seems to lean on the fact that California had previously legalized same-sex marriage, and that this right was eliminated by Proposition 8; it doesn’t address the broader question of whether it’s unconstitutional to deny marriage to same-sex couples in states that have never previously recognized such relationships.

Expect an appeal to the U.S. Supreme Court—which, let’s not speculate what they’ll do just yet. ◼

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Don’t they know how to use Google?

Tonight is caucus night in my adoptive state of Minnesota, and I’m mildly embarrassed to see polling that puts Rick Santorum in the lead with state Republicans. I like to see the GOP make a collective ass of itself as much as the next cog in the Democratic machine, but I wouldn’t wish Santorum on anyone—not even the debt-ridden party that shut down our state government last summer. ◼

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Science online, how we got this way edition

Actually, they’re kind of the opposite of “solo” cups. Photo by arvindgrover.

Video of the week, via io9: a “fly-through” view of a nebula, created by NASA using data from the Hubble Space Telescope. Am I the only one who hears the Star Trek: Voyager theme while this plays?


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