Grizzly bear. Photo by Alaska Dude.The latest edition of the Carnival of Evolution, a monthly collection of online writing about evolution and all its ramifications, is online at Sandwalk. Check it out to learn why genetic testing for grizzly bears is important, what new fossil may have taken the place of Archeopteryx in the evolutionary history of birds, and what pioneer of evolutionary biology will soon be on a U.S. postage stamp.
Freddie Fungus and Alice Algae have no likin’ for prions. Photo by 0olong.
High-elevation populations of deer mice have evolved “stickier” hemoglobin to cope with the thin atmosphere. (Animal Diversity Web)
It’s easy to walk through the woods and fields of North America and never spot Peromyscus maniculatus, the deer mouse, but you’ve probably heard them scampering off through the leaf litter or under cover of tall grass. They’re exceptionally widespread little rodents, found in forest undergrowth and fields from central Mexico all the way north to the Arctic treeline. In all this range, they look about the same: small and brown, with white underparts and big, sensitive ears.
That apparent sameness is deceptive, however.
A big, varied range presents lots of different environmental conditions to which a widespread species must adapt. And when that big, varied range includes the Rocky Mountains, one of those environmental conditions is as basic as the air itself. At high altitudes, atmospheric pressure is lower, which means lower partial pressure of oxygen, the gas that makes life as we know it work.
The fundamental problem at high altitude is to pull more oxygen from thinner air. Natural selection is good at solving problems, and it has multiple options for adapting a mammal to thinner air at high altitudes, to the extent that these traits are heritable. Selection could favor individuals who more readily respond to thin air by breathing faster and deeper, pulling in more air to make up for its lower oxygen content. Or selection could favor individuals who produce more red blood cells, so that a given volume of blood pumped through their lungs picks up more oxygen. Or, at the most basic level, selection could favor individuals whose individual red blood cells are better at picking up oxygen, via a new form of hemoglobin, the oxygen-binding molecule that packs every red blood cell.
A pseudonym is an identity.
It may not be the identity with which the pseudonymous person was born, but it’s an identity nevertheless. Far more excellent writers than I write online under pseudonyms, building up reputations around those not-given-at-birth names that are every bit as valid as whatever praise or contempt I’ve earned under my given-at-birth one.
Furthermore, there are some excellent reasons (see under “Bosses, not with it” and “Stalkers, online and otherwise” and “Crackpots, fielding endless e-mails from”) that given-at-birth identities can be risky online, and potentially disproportionately risky for women. Which is to say, disproportionately risky for, um, half of everyone everywhere.
Which is why it’s frankly rather silly and shortsighted of Google+, the hot new social network of the moment, to be closing accounts registered under pseudonyms. I mean, I understand that the big G would consider identities associated with, e.g., actual credit card accounts and consumer behaviors, to be strongly preferable. But if I were building a social network, I think I’d probably want Scicurious in it, because even if I can’t get useful consumer behavior data out of her pseudonymous profile, I’ll bet there are people who would join a not-quite-baked social network if it meant yet another opportunity to watch the fun when Sci puts on her ranty pants.
Which is to say, if you’re trying to get people to join a club, you really don’t want to kick out all the cool kids.
So, hey, there’s a petition you could sign, if you think maybe Google should know they’re being a mite dense about this whole thing. It is, as they say, the least you can do.
This organic breakfast may not be “chemical free,” but it could change your brain. Photo by lauren glanzer.Special congratulations this week to Ed Yong, who is officially a full-time freelance writer as of Wednesday. I can only imagine what he’ll achieve now that this science writing thing isn’t restricted to his spare time.
It’s nice to be living in a blue state. I just wish that it wasn’t necessary to move halfway across the country to finally acquire a Congressional delegation that actually reflects my values.
A brown anole, with dewlap extended. Photo by jerryoldnettel.Last June, I discussed a study with big ambitions: to experimentally compare the effects that competition and predators have on island populations of brown anoles, Anolis sagrei. Now the current issue of the journal that carried that study, Nature has a brief communication from the godfather of anole evolutionary ecology himself, Jonathan Losos. Losos and his coauthor Robert Pringle raise some serious questions [$a] about the results of that experiment.
The authors of the original study [$a], Ryan Calsbeek and Robert Cox, concluded that competition was more important than predation because natural selection acting on anoles was stronger on experimental islands with higher anole population density, while the presence or absence of predators on those islands made no difference in the strength of selection. Losos and Pringle object that anole population density is entangled with other factors that may make Calsbeek and Cox’s results uninterpretable.
This experimental design is confounded in three fundamental ways. First, density is confounded with island area. All analyses treat lizard density as a surrogate for intraspecific competition. However, an inverse correlation with island area explains 95% of the variation in density, such that it is impossible to disentangle the two factors statistically. This is a crucial problem, because multiple factors related to both predation and competition are known to vary with island area. For example, as island area increases, so too do the number of bird species (which increases the number of potential predators) and mean vegetation height (which might increase lizards’ susceptibility to avian predation). Likewise, because larger islands have lower perimeter/area ratios, they receive relatively lower input of marine-resource subsidies and have lower arthropod densities; a study of A. sagrei in this system showed that lizard densities vary significantly with the amount of seaweed deposition, and that experimental seaweed deposition increased lizard densities by more than 60%. [In-text citations removed for clarity.]
That point alone is a pretty big problem with Calsbeek and Cox’s result. Then Losos and Pringle re-analyze the data presented in the original study, and discover the very odd result that anoles in the experimental populations had higher rates of survivorship on the high-density islands—which is exactly the opposite of what you’d expect if competition for important resources were more intense in high-density populations. At the very least, this indicates that there could be more going on than Calsbeek and Cox originally supposed, in which case their data don’t support their conclusions.
Losos and Pringle raise other objections, including the issue of small sample size I noted in my original post. You should read the whole thing [$a] for the details, as well as the response [$a] from Calsbeek and Cox.
References
Calsbeek, R., & Cox, R. (2010). Experimentally assessing the relative importance of predation and competition as agents of selection. Nature, 465 (7298), 613-616 DOI: 10.1038/nature09020
Calsbeek, R., & Cox, R. (2011). Calsbeek & Cox reply. Nature, 475 (7355) DOI: 10.1038/nature10141
Losos, J., & Pringle, R. (2011). Competition, predation and natural selection in island lizards. Nature, 475 (7355) DOI: 10.1038/nature10140
Via The Dish, which I haven’t read in ages: Bryan Caplan distills pacifism into a comparison of E[benefits of war] and E[costs of war]. That is, we know wars are expensive and awful, but we have much less assurance that they’re going to be worth it:
Of course, “Fight when it’s a good idea, make peace when it’s a good idea” counts as a philosophy. And you might think that this case-by-case approach has to yield better results than pacifism. But that’s only true with perfect foresight. In the real world of uncertainty, case-by-case optimization is often inferior to simple rules.
Which is why I tend to think of pacifism as a small-c conservative position: simple risk-benefit analysis, and a little honest evaluation of history.
A queen bee, indicated with a red dot of paint. Photo by reway2007.I’m super late to this one, but … holy blithering wow, man.
Dan Savage—nationally syndicated advice columnist, It Gets Better co-founder, serial contributor to This American Life, and all around alpha-gay—was on the Colbert Report to discuss the recent New York Times profile about his views on monogamy, which views may be briefly summed up as why ruin a perfectly good marriage by insisting on complete sexual fidelity? And about midway through said interview, Savage drops a line which, while requiring no censorious bleeping whatsoever, stops Colbert dead in his metaphorical and satirical tracks and had me just about on the floor in laughter and/or amazement. I’m frankly still a mite breathless, and in full-on Wallace-esque run-on mode as a result.
And, well, you probably don’t want to see it if you’re not particularly cool with Savage’s aforementioned feelings about monogamy, but if you are in fact generally on board or at least don’t get the howling fantods after reading my summary or obliquely contemplating what I shall delicately call the mechanics of love, and if you are even later to this than I am* you really ought to right now.
| The Colbert Report | Mon – Thurs 11:30pm / 10:30c | |||
| Dan Savage | ||||
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All of which is a rather long way to go to say, gods (or whoever) bless Dan Savage and Stephen Colbert.
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*Which probably means you didn’t have an internet connection till this evening, in which case let me take this footnote to say, welcome to the World Wide Web!
