Not all species interactions are (co)evolved equal

Biologists have long thought that coevolutionary interactions between species help to generate greater biological diversity. This idea goes all the way back to The Origin of Species, in which Darwin proposed that natural selection generated by competition for resources helped cause species to diverge over time:

Natural selection, also, leads to divergence of character; for more living beings can be supported on the same area the more they diverge in structure, habits, and constitution, of which we see proof by looking at the inhabitants of any small spot or at naturalised productions.
—Darwin (1859), page 128.

In the twentieth century, this idea was extended into suggestions that coevolution between plants and herbivores or flowers and pollinators helped to generate the tremendous diversity of flowering plants we see today. In general, biologists have found that strong coevolutionary interactions are indeed associated with greater diversity.

Yet although there is a well-established association between coevolution and evolutionary diversification, correlation isn’t causation. Furthermore, every species may coevolve with many others, and diversification that seems to be driven by one type of interaction might actually be better explained by another. It has even been suggested that coevolution rarely causes speciation at all.

Species interact in a lot of different ways, as antagonists, competitors, and mutualists. Do all these interactions shape diversity the same way? (Flickr: jby)

One step toward determining how often coevolution promotes diversification would be to identify what kinds of coevolutionary interaction are more likely to generate diversity. This is precisely the goal of a paper I’ve just published with Scott Nuismer in this month’s issue of The American Naturalist. In it, we present a single mathematical model that compares a wide range of species interactions to see how they shape diversification, and that model shows that coevolution doesn’t always promote diversity [PDF].

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Pardon the dust

I’ve been fiddling with D&T’s formatting yesterday and today, mainly because I want to use a more up-to-date version of Blogger’s template system, including slightly shinier integration of stand-alone pages and the native post-sharing buttons. I think I’ve finally got things about the way I want them.


Science online, inhospitable conditions edition

Precarious, yes, but he’s protecting his sperm count. Photo by Ed Yourdon.
  • Don’t roast your junk, dude. Scicurious takes on the recent study showing that laptop computers can raise dudes’ scrotal temperatures, putting their sperm at risk. (Neurotic Physiology)
  • In case you needed another reason to hate them. A grad student specializing in mutation repair mechanisms considers the risk of the TSA’s new X-ray backscatter body scanners. (My Helical Tryst)
  • Too late to change the name to Phoenix? The neuroscience blog carnival Encephalon is back, in spades. (A Blog Around the Clock)
  • It’s that time of year again. Bora kicks off the lead-up to ScienceOnline 2011 with a series of posts introducing registered participants. (A Blog Around the Clock)
  • More than cat videos. Jonathan Eisen lists the ways blogging and microblogging have contributed to his scientific career. (The Tree of Life)
  • Actually, it’s just an eternal dissertation defense. Neuroskeptic imagines what scientific Hell would be like. (Neuroskeptic)
  • Waterproof sunscreen, anyone? Depletion of the ozone layer may mean whales are at greater risk of sunburn—and skin cancer. (Mental Floss, original article in Proc. Royal Soc. B)
  • Preadaptation for the win. One of the few Australian predators that can tolerate invasive cane toads is a snake that may have evolved the tolerance in response to selection from toxic prey in its ancestral range. (Oh, For the Love of Science)
  • NASA has not found extraterrestrial life. But it has found bacteria that use arsenic in place of phosphorous, which means there’s one more form extraterrestrial life could take. (Nature News, NY Times, Not Exactly Rocket Science; original article in Science [$a])

Regarding that last item, I’ll give the final word to good ol’ xkcd.

Comic by xkcd.

Close the Washington Monument

Security expert Bruce Schneier thinks that we should close the Washington Monument. The most distinctive part of the D.C. skyline has been a challenge to secure, but that’s not Schneier’s reason.

An empty Washington Monument would serve as a constant reminder to those on Capitol Hill that they are afraid of the terrorists and what they could do. They’re afraid that by speaking honestly about the impossibility of attaining absolute security or the inevitability of terrorism — or that some American ideals are worth maintaining even in the face of adversity — they will be branded as “soft on terror.” And they’re afraid that Americans would vote them out of office if another attack occurred. Perhaps they’re right, but what has happened to leaders who aren’t afraid? What has happened to “the only thing we have to fear is fear itself”?

An empty Washington Monument would symbolize our lawmakers’ inability to take that kind of stand — and their inability to truly lead.

Go read the whole thing.

Photo by Scott Ableman.