Not all species interactions are (co)evolved equal

Posted on by

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].

Continue reading →

Pardon the dust

Posted on by

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.

Getting into the spirit

Posted on by

There’s nothing like purchasing a grocery bag full of sugar and butter and dark rum and downloading a new Pink Martini holiday album to put me in that Saturnalian spirit. Happy holidays.

Posted in Uncategorized | Tagged ,

Science online, inhospitable conditions edition

Posted on by
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.

Carnival of Evolution No. 30

Posted on by
Photo by ricmcarthur.

Or maybe it should be Carnival of Evolution XXX? Anyway, it’s online at This Scientific Life, and full of good posts from all over the evolution-inclined science blogosphere. Go check it out!

Close the Washington Monument

Posted on by

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.

Nibbled to distraction: Gerbils infested with fleas don’t watch for foxes

Posted on by

ResearchBlogging.orgIn natural communities, each species is embedded in a web of interactions with other species—predators, prey, competitors, mutualists, and parasites. The effects of all these other species combine in complex, unpredictable ways. I recently discussed a study of protozoans living inside pitcher plants that found predators and competitors can cancel out each others’ evolutionary effects. Now another study finds that parasites and predators can interact to make desert-living gerbils adopt less effective foraging strategies [$a].

Allenby’s gerbil is a small desert rodent native to Israel’s Negev Desert. They make a living foraging for seeds, which might seem simple enough—but for small desert mammals, it’s a constant balancing act. Foraging requires continuously judging how profitable it is to continue gathering seeds in one spot compared to looking for another, maybe better, spot; and all the while watching out for predators.

The red fox—a major threat if you’re a tiny rodent, but hard to watch for when you’re scratching fleas all the time. Photo by HyperViper.

For small mammals, parasites like fleas can impose a real physiological cost—but they might also cause irritation that interfere with effective foraging. This idea led a group of Israeli reserachers to experimentally infest captive gerbils with fleas, and release them into an enclosure with a red fox.

It’s okay—the fox was muzzled! The research group was interested in how effectively the gerbils foraged in standardized patches of resources (trays of seed mixed with sand) in the presence of predators, and how being flea-ridden changed that foraging behavior. As metrics of foraging efficiency, they recorded how rapidly the gerbils gave up foraging in a single tray before moving on to another, which approximates how many seeds they left behind.

With no fleas, gerbils spent slightly—but not significantly—less time foraging in a single tray when a fox was in the enclosure with them. But gerbils infested with fleas moved on to a new tray substantially faster in the presence of a fox, leaving behind more seeds in the process. The study’s authors suggest that this is because the irritation caused by fleas distracted the gerbils too much to keep watch for a predator and forage at the same time—so flea-ridden gerbils made up for being less watchful by moving between patches of resources more rapidly.

So for gerbils, the presence of a second, different kind of antagonist amplifies the effects of a nearby predator. Fleas and foxes aren’t just a double whammy—the effects of both together are worse than the sum of each individually.

Reference

Raveh, A., Kotler, B., Abramsky, Z., & Krasnov, B. (2010). Driven to distraction: detecting the hidden costs of flea parasitism through foraging behaviour in gerbils. Ecology Letters DOI: 10.1111/j.1461-0248.2010.01549.x

Running the race

Posted on by

Well, I’ve successfully run the Seattle Marathon. I finished in 3 hours, 31 minutes, and 27 seconds, which is a pretty nice improvement over last time, in Portland.

Coming down the home stretch. Photo courtesy my cousin Adrienne.

I’ve had a nice hot shower, and my cousin—with whom I’m staying while in Seattle, and who came to watch me cross the finish line—keeps pressing protein-and-vitamin recovery shakes on me, so I’m actually feeling pretty good. It’s great end to a great fall break in Vancouver and Seattle. I took a lot of photos—there’s a slideshow after the jump.

Posted in Uncategorized | Tagged ,

Science online, Black Friday edition

Posted on by
There may be more going on in those tiny heads than you think. Photo by shadarington.
  • Attention, bacon fans. Epileptic seizures can be controlled by an ultra-high-fat diet. (NY Times)
  • A few mg of prevention. Men who have sex with men can substantially reduce their risk of HIV infection by taking antiretroviral drugs. (NY Times, Dan Savage; original article in The New England Journal of Medicine)
  • Oh, now you tell us. Turkeys have enough social intelligence to recognize other turkeys from their own social group. (Jason Goldman for Scientific American)
  • Mmm. Cranberry genomics. Jason Goldman rounds up Thanksgiving-themed online science writing. (The Thoughtful Animal)
  • Meta-blogging science? The fellows behind Obesity Panacea have launched a blog about science blogging. (Science of Blogging)
  • A pithy comment is beyond the scope of the present linkfest. Incremental publication can be a good thing. (DrugMonkey)
  • Well, that was easy. A simple 15-minute writing assignment closes the “gender gap” between male and female physics students. (Not Exactly Rocket Science)
  • To be fair, science is pretty difficult. The leadership of the American Anthropological Association is moving to remove references to science from the organization’s mission statement. (Fetishes I Don’t Get)

And finally, Robert Krulwich narrates a beautifully animated short film about an enduring mystery of human behavior: our inability to walk in a straight line without help from visual cues.

No, I will not run the Seattle Marathon barefoot

Posted on by

My first marathon was last year’s Portland Marathon. Prior to 2009, I’d never run a race longer than five miles, but then that spring I let friends talk me into a half-marathon, and after running more than 13 miles, 26.2 suddenly didn’t seem quite so insane. Even so, training up for Portland was more than enough to make me realize that running what was (for me) a 3 hour-45 minute course is not really the same thing as running eight or nine 5k’s in a row.

Feed me!

Me at about mile 17 in last year’s Portland Marathon. I’m not quite dead yet.

I can make it through even a half-marathon on a good breakfast and carefully-judged pre-race hydration, but to go much longer I need more food (and water) mid-run. The long-term exercise involved in a long race is fueled by a combination of fat reserves and glycogen stored in the liver and muscle tissue. Glycogen is the more efficient fuel, so as exercise intensity increases, muscles draw on it more heavily.

If his muscles runs out of glycogen, a runner “hits the wall,” and may be forced to stop running altogether. I’ve done this a few times on long training runs, and it’s not pleasant—I’d end up all but walking the last couple painful miles. How long I can go before I hit the wall depends on my glycogen reserves, which in turn depend on the muscle mass in my legs—but it also depends on how fast I’m running, since glycogen use increases with effort. A computational study of the interactions between exercise intensity and glycogen consumption suggests that my first marathon time, 3:45, was close to the upper limit of glycogen consumption for a “trained endurance athlete”—and I probably don’t really qualify as “trained,” in the sense the study uses. So to survive a marathon, I have to take on supplementary energy mid-race, for which I will carry tubes of disgusting sugar syrup.

Continue reading →