Interview at Coyote Crossing

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Nature writer and photographer Chris Clarke is a great fan of yuccas and yucca moths—he’s working on a book about Joshua trees right now—and so he asked me to answer a few questions about the latest research on the evolutionary history of yucca moths, which was just published in the Biological Journal of the Linnean Society. Check out Clarke’s discussion of the mutualism, and our e-mailed interview, on his blog Coyote Crossing. Look for a post about the paper, with some basic explanation of the methods used in it, right here at D&T next Tuesday.

Ladybird beetle on a Joshua tree leaf. Photo by jby.

Where’s Harry Tuttle when you need him?

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I just finished the most emotionally draining telephone exchange I think I’ve ever had. It was with my primary health care provider, concerning the surprisingly thorny question of services received versus services requested versus services covered by my health insurance. I’d been trying to get an answer for more than a week, and it was implied that this was expecting a little too much.

I was exceptionally non-Mennonite. I was sarcastic with a total stranger. I asked to speak to someone’s supervisor. It did not, however, occur to me to ask for the 27B-6. Maybe that would’ve done the trick.

Still more #sbFAIL fallout: Bora bails

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Photo by Roadsidepictures.

It seemed as though the dust had finally settled over the ScienceBlogs/Pepsi fiasco—until yesterday, when another shoe dropped, and it was a big one. In a typically thorough, nuanced post, Bora Zivkovic announced his decision to leave ScienceBlogs, relocating to WordPress.

If you’ll pardon the use of a horrible business buzzword, Bora is a super-connector, spending more effort than anyone else in my blogroll to pass on links, making the ScienceOnline conference a network-y blast, and offering nods to junior members of the online science writing community. In his departure essay, he makes it clear that this kind of connectivity is the point of blogs in general, and the power of ScienceBlogs in particular:

That is huge power. I keep mentioning this power every now and then (see this, this, this and this for good examples) because it is real. Sustained and relentless blogging by many SciBlings (and then many other bloggers who followed our lead) played a large role in the eventual release of ‘Tripoli Six’, the Bulgarian medical team imprisoned in Libya. Sustained blogging by SciBlings (and others who first saw it here) played a large part in educating the U.S.Senate about the importance of passing the NIH open access bill with its language intact. Blogging by SciBlings uncovered a number of different wrongdoings in ways that forced the powers-that-be to rectify them. Blogging by SciBlings brings in a lot of money every October to the DonorsChoose action. Sustained blogging by SciBlings forced SEED to remove the offending Pepsi blog within 36 hours. And if a bunch of SciBlings attack a person who did something very wrong, that person will have to spend years trying to get Google to show something a little bit more positive in top 100 hits when one googles their name (which is why I try to bite my tongue and sleep over it when I feel the temptation to go after a person). The power of the networks of individuals affects many aspects of the society, including the media. [Hyperlinks sic.]

Losing someone who believed so deeply in the social power of the blog network, and who worked so hard to boost that power and channel it to good ends, is a huge blow to ScienceBlogs. It seems to have contributed to PalMD’s decision to quit SB, and decisions by PZ Myers and Greg Laden to go on blog-strike. And now that Bora has joined the ScienceBlogs diaspora, it’ll be interesting to see how his super-connecting shapes the emerging community of independent blogs.

Sex after dawn: Marriage and natural selection

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ResearchBlogging.orgThe book Sex at Dawn, by Christopher Ryan and Cacilda Jethá, has had a lot of press in the last month—it first popped up on my radar with Eric Michael Johnson’s review for SEED, and then it became unavoidable (for me, anyway) when Dan Savage devoted a whole column and podcast to it. The thesis of Sex at Dawn is that early humans were highly promiscuous, and that modern expectations of monogamy are probably not consistent with our biology. I haven’t read the book yet, but the discussion surrounding it has largely missed an important detail—human evolution didn’t stop when we invented agriculture.

In fact, we’ve evolved in response to agriculture. My capacity to digest milk proteins at age 28—most other mammals lose this ability as soon as they’re old enough for solid food—is the result of natural selection acting on my northern European ancestors. Sex at Dawn coauthor Christopher Ryan acknowledges exactly this, citing the same example, in a recent response to a question on his blog. I’m not aware of a study that documents human evolution in response to marriage customs, but conveniently enough, an article in the current issue of The American Naturalist does show that a population’s marital customs can shape its response to natural selection [$a].

Vintage postcard via chicks57.

The intensity and nature of natural selection often varies with age—it’s strongest on traits expressed prior to and during the period of life when most reproduction happens, and weaker on traits having to do with life after reproduction is mostly complete.

The new paper examines the effect of marriage on this relationship between age, reproductive activity, and the strength of natural selection. The authors are able to do this thanks to church records of births (via christenings), marriages, and deaths from four Finnish towns during the nineteenth century—a deep multigenerational dataset. The society described is probably as far away from the Sex at Dawn world of communal relationships within hunter-gatherer tribes as Western society has ever gotten—the births recorded are all in the context of monogamous marriages. How monogamous these marriages actually were is debatable; this was also a world before paternity testing. But the study follows women, who would probably have had less opportunity, and certainly had less social leeway, for affairs outside marriage.

Within that society, women’s reproductive success depended strongly on their husbands’ economic status, as approximated by whether or not they owned land. Women who married landowners married almost three years earlier, on average, than those who married non-landowners (between 24 and 25 years old, compared to 27). Women who married at an earlier age generally had more children survive to age 15, the paper’s benchmark for lifetime fitness—and this effect was stronger for women who married landowners.

Vintage wedding portrait via freeparking.

This meant that the intensity of potential natural selection acting on women in the study group peaked around their 30th birthday, declined slowly for around a decade, and then dropped off sharply. By comparison, an estimate of selection intensity based only the women’s probability of survival to a given age (i.e., without accounting for the need to marry before having children) just shows a steady decline with age. So marriage customs probably shaped the way natural selection could act on this population. (The comparison made, though, is a pretty facile one. I’d love to know what the intensity of selection looks like under other post-agricultural mating systems like, say, polygyny.)

Does that mean that these nineteenth-century Finns were evolving in response to the strictures of monogamy? Not necessarily. This study only estimates how strong selection would be on a trait relative to the age at which it’s expressed. That is, traits that reduced (or improved) a woman’s ability to bear children would be more strongly selected against (or favored), if they were expressed while she was between the ages of 30 and 40.

So the fact that marriage customs shape natural selection doesn’t mean that we’ve evolved to be better adapted to current marriage customs than we are to those of pre-agricultural hunter-gatherers. Marriage customs vary considerably among cultures, and over time—I don’t know of any culture that has maintained strict monogamy since the origin of agriculture. Even if a single culture did prefer monogamy that long, natural selection to adapt to that mating system would be working from a pool of genetic variation evolved from hundreds of generations of our earlier polyamorous lifestyle. It doesn’t matter how strongly natural selection would favor a perfectly monogamous person, if such a person doesn’t exist.

In other words, the key insight of Sex at Dawn—which is also a key insight of evolutionary biology in general—is right: What we can become is shaped by what we used to be. That’s certainly an important thing to keep in mind when considering a commitment that lasts till death do you part.

(For example, you might want to makes sure your significant other is of at least the same genus as you. I mean, talk about biological impediments.)

References

Gillespie, D., Lahdenperä, M., Russell, A., & Lummaa, V. (2010). Pair-bonding modifies the age-specific intensities of natural selection on human female fecundity. The American Naturalist, 176 (2), 159-69 DOI: 10.1086/653668

Science online, hermit crab hand-me-down edition

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Got anything in a size 6? Photo by Vanessa Pike-Russell.
  • Gushing no more? No, the oil gusher in the Gulf of Mexico is not going to release a giant, world-killing methane bubble. Reality is bad enough. BP spent the week putting a new cap in place over the well, and … it seems to be working. Which still leaves an enormous cleanup to complete, and begs the question of why they weren’t prepared to do that 88 days ago. As always, Dr. M. at Deep Sea News is your one stop shop for oil spill news.
  • More kinds of herbivores = less plant damage. Organic farms support more evenly distributed communities of plant-eating critters, which turns out to be good for the plants. (The EEB & flow)
  • Of course, then they’re stuck with last year’s model. When they find an empty shell that’s too big for them, hermit crabs wait for a larger crab to come along and claim it, so they can occupy the cast-off shell. (MattSoniak.com)
  • Any evidence of recent vuvuzela-induced selection? A mutant form of a single gene is associated with temperature-dependent hearing loss. (Code for Life)
  • How to get MSNBC to notice a paper about protein structures: Claim you’re answering an age-old philosophical riddle that you’re not, actually. (MSNBC)

Which came first, the silly scientific hype, or the flimsy excuse to run a Muppet video? Trick question; they’re the same thing.

Don’t look now

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… but, if you’re in a part of the world where it’s summer, there are billions of insects flying thousands of feet above your head right now. Robert Krulwich tells you all about them in this charmingly animated bit from NPR.

In other news, NPR is now producing embeddable videos! Way to surf the new-media wave, guys!

When ecological opportunity knocks, does adaptive radiation answer?

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ResearchBlogging.orgOne of the most basic questions in evolutionary ecology is, “why are there more kinds of this kind of critter than that kind of critter?” As in, why are there more than twenty thousand species of orchids, but only one species of ginkgo? Why are there hundreds of thousands of species of beetles, but only four species of horseshoe crab? In a literature review just released online—and my first publication as lead author!—my coauthors and I assess the support for one hypothesis: that species multiply because of ecological opportunity.

Biologists interested in the origins of species diversity frequently focus on the phenomenon of adaptive radiation, the process by which a single species rapidly gives rise to many new species, each with different traits adapted to different lifestyles. Darwin’s finches, with their beaks shaped to suit to different foods [$a], are a classic case; the Anolis lizards of the Caribbean, which have repeatedly evolved into a handful of “ecomorphs” with different body sizes and shapes adapted to different perching locations [PDF], are another.

Why are there so many [insert taxon here]? Photos by Bill & Mark Bell (1 & 2), fturmog (3 & 4).

The two most influential theories of adaptive radiation—by G.G. Simpson and Dolph Schluter—have suggested that it results when a species encounters ecological opportunity. Ecological opportunity might be a newly-evolved trait, or a new habitat, or the extinction of a species’ competitors or predators. For instance, a butterfly might evolve a way to overcome the chemical defenses of an abundant plant species, or a plant introduced by humans to a new habitat might find that local pathogens aren’t as deadly to it as the ones in its native range. Ecological opportunities have the effect of granting access to new resources. We have pretty good evidence that this can allow individual populations to increase in number, and even evolve greater diversity—but is that enough to spur the rapid speciation that forms adaptive radiation?

Ecological opportunity ? adaptive radiation

We’re pretty sure about steps 1 and 3. We’re still trying to figure out step 2.

Readers in certain demographic groups may think this sounds like an underpants gnome problem. But it isn’t, exactly. The gnomes’ business model can’t get to from step 1 (collect underpants) to step 3 (profit) because they don’t have a step 2. Evolutionary ecologists, on the other hand, already have their step 3 in the phenomenon of adaptive radiation. Ecological opportunity looks like a good prospect for step 1 precisely because it suggests some plausible options for step 2.

When a population encounters ecological opportunity, the new habitat, new trait, or extinction of antagonists provides access to new resources, and relaxes natural selection on the population. This leads to three phenomena usually grouped together under the term ecological release

  • The population experiences density compensation—more individuals can live in a particular area, creating stronger competition within the population.
  • Because of this stronger competition within the population, or because there isn’t much competition from other species, members of the population venture into new habitats, or use new food resources.
  • The population becomes more diverse, either because of the relaxed selection, or because of competition-driven selection for using new habitat and new resources.

One or more of these three aspects of ecological release turn up whenever populations find new food resources, or escape predators and/or competitors. Density compensation has been widely observed in populations colonizing new habitats, especially islands; and experiments with sticklebacks and fruit flies [$a] suggest that the stronger competition resulting from density compensation can spur the population to become more diverse in its use of resources. Bacterial populations can even evolve different specialized forms—adaptive radiations in microcosm—when introduced to new food resources.

Anoles show signs of density compensation on Caribbean islands—is that the reason behind their diversification? (Pictured: Anolis oculatus.) Photo via WikiMedia Commons

But where’s the speciation?

However, the evolution of bigger, more diverse populations is not the same thing as the evolution of new species—and that’s what adaptive radiation is really all about. These changes resulting from ecological opportunity might directly promote speciation if stronger competition leads to disruptive natural selection. Similarly, the competition-driven incentive to colonize new habitats or exploit new food sources could expose some parts of the population to different forms of natural selection, eventually causing them to evolve into specialists on the new resources. Finally, even if speciation only happens when natural barriers cut off migration, maybe larger, more variable populations provide more diversity for vicariance events to divvy up.

This is all pretty speculative, though. We still don’t know how often—or how rarely—divergent natural selection contributes to making new species. One way to deal with this is to approach the question from the other direction: look backward at the history of existing species, rather than following what happens to populations immediately after ecological release.

A backward-looking approach might use statistical analyses of the evolutionary relationships between living things to identify points in time when species formed unusually fast, and try to identify the cause. Some of my coauthors from the review paper recently published an analysis of the evolutionary tree connecting all vertebrates, and found that speciation rates increased around the origins of the largest group of birds, a large portion of the lizards and snakes, and non-marsupial mammals, among others.

This is very much a starting point, but maybe by complementing similar studies with research on populations currently evolving in response to ecological opportunity, biologists can work our way closer to understanding the origins of the endless and beautiful forms of life on Earth.

References

Alfaro, M., Santini, F., Brock, C., Alamillo, H., Dornburg, A., Rabosky, D., Carnevale, G., & Harmon, L. (2009). Nine exceptional radiations plus high turnover explain species diversity in jawed vertebrates. Proc. Nat. Acad. Sci. USA, 106 (32), 13410-4 DOI: 10.1073/pnas.0811087106

Bolnick, D. (2001). Intraspecific competition favours niche width expansion in Drosophila melanogaster. Nature, 410 (6827), 463-6 DOI: 10.1038/35068555

Blumenthal, D., Mitchell, C., Pysek, P., & Jarosik, V. (2009). Synergy between pathogen release and resource availability in plant invasion. Proc. Nat. Acad. Sci. USA, 106 (19), 7899-904 DOI: 10.1073/pnas.0812607106

Grant, B., & Grant, P. (1989). Natural selection in a population of Darwin’s finches. The American Naturalist, 133 (3), 377-93 DOI: 10.1086/284924

Kassen, R. (2009). Toward a general theory of adaptive radiation: Insights from microbial experimental evolution. Annals New York Acad. Sci., 1168 (1), 3-22 DOI: 10.1111/j.1749-6632.2009.04574.x

Losos, J. (1990). Ecomorphology, performance capability, and scaling of West Indian Anolis lizards: An evolutionary analysis. Ecological Monographs, 60 (3), 369-88 DOI: 10.2307/1943062

Schluter, D. 2000. The Ecology of Adaptive Radiation. Oxford University Press. Google Books.

Simpson, G.G. 1949. Tempo and Mode in Evolution. Columbia University Press. Google Books

Svanbäck, R., & Bolnick, D. (2007). Intraspecific competition drives increased resource use diversity within a natural population. Proc. Royal Soc. B, 274 (1611), 839-44 DOI: 10.1098/rspb.2006.0198

Wheat, C., Vogel, H., Wittstock, U., Braby, M., Underwood, D., & Mitchell-Olds, T. (2007). The genetic basis of a plant insect coevolutionary key innovation. Proc. Nat. Acad. Sci. USA, 104 (51), 20427-31 DOI: 10.1073/pnas.0706229104

Yoder, J.B., Des Roches, S., Eastman, J.M., Gentry, L., Godsoe, W.K.W., Hagey, T., Jochimsen, D., Oswald, B.P., Robertson, J., Sarver, B.A.J., Schenk, J.J., Spear, S.F., & Harmon, L.J. (2010). Ecological opportunity and the origin of adaptive radiations. Journal of Evolutionary Biology DOI: 10.1111/j.1420-9101.2010.02029.x

Science online, not so pristine anymore edition

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I’ll start with the online science meta-news: The ScienceBlogs PepsiCo saga achieved a preliminary resolution yesterday, when Science Blogs pulled the PepsiCo blog. Many SBers who left in protest, however, are apparently not returning, including Brian Switek (of Laelaps) and Rebecca Skloot. Skullsinthestars has taken on the public service of tracking departing SBers, which include some of the biggest names on the site. Carl Zimmer compiles his own list, and adds some scathing remarks. David Dobbs gave his reasons for not returning, Martin Robbins of the Lay Scientist neatly summed up the issues of reader trust and respect for individual writers underlying the fracas, and Curtis Brainard weighed in at the Columbia Journalism Review. No word yet on coverage by On the Media, but I’m still hoping.

Say it ain’t so, Glacier National Park. Photo by jby.

Meanwhile, in actual science news:

  • Still gushing. As of today (Friday), it’s been 81 days since BP broke the Gulf. Yet another projection of long-term surface dispersal of the oil suggests the U.S. east coast is in trouble. At Deep Sea News, Dr. M rounds up the latest news and Allie Wilkinson flies over the slick with the Coast Guard. Meanwhile ProPublica digs into BP’s horrendous safety record and foot-dragging on compensation and cooperation with scientists.
  • Missed this earlier. BlagHag reports on Portland and Evolution 2010.
  • I’m confused. What about spinach? A new study of bone structure suggests Neanderthals were totally pumped, with “Popeye-like forearms,” possibly because of a highly carnivorous diet. (Discovery News)
  • Well, it doesn’t look its age. New fossils reveal that multicellular life is at least 2.1 billion years old, more than three times as old as previously thought. (ScienceDaily)
  • This just makes me sad. Environmental pollutants, including pesticides, are extensive at national parks—with particularly bad levels at Glacier and Sequoia. (Conservation Maven)
  • It works for cpDNA, anyway. A new method for extraction and amplification of DNA from plant tissue may make life simpler for lab rats like me. (Uncommon Ground)
  • Cichlids do it wherever they can. Since colonizing a volcanic crater lake in Nicaragua—as little as a century ago—a population of Midas cichlid fish has evolved into two distinct forms, with marked dietary differences. (NeuroDojo)
  • Dudes should not wear corsets. Because they may cause you to grow a bone in your penis. Really. (scicurious)

And, as a video-based closing thought, here’s footage of a cuckoo chick evicting the other eggs—and chicks!—in its adoptive nest. The initial, um, cuckholding is captured here

Science Blogs in refreshing, sugary ethics kerfuffle

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ScienceBlogs, the mothership of online nerdery, just made a big, bad-publicity splash, launching a nutrition-themed blog sponsored—and written—by PepsiCo.

Photo by Roadsidepictures.

Readers have been irked, and many ScienceBloggers, for whom this apparently came as a surprise, are expressing feelings ranging from barn-burning outrage to nuanced concern to biting dismissal—and also resigning in protest (or exhaustion). It isn’t the first time ScienceBlogs has run a corporate-sponsored column, but those previous ones had writers who were independent of the sponsor. The affiliations of the new blog, Food Frontiers, are indicated in the header bar and the masthead, but not especially loudly—and the blog’s content will apparently be aggregated to Google News alongside the work of non-corporate ScienceBloggers. As Knight Science Journalism points out, ScienceBlogs’ treatment of Food Frontiers pretty clearly violates old media journalistic ethics.

In an e-mail to ScienceBloggers leaked to The Guardian, SEED editor Adam Bly wrote

We think the conversation should include scientists from academia and government; we also think it should include scientists from industry. Because industry is increasingly the interface between science and society. It is our hope that the Xeroxes and Bell Labs of the future will have a real presence on SB – that they will learn from our readers and we will learn from them.

That’s a pretty poor equivalency Bly is making, frankly. As far as I can tell, the academic scientists who write for ScienceBlogs do so without an explicit mandate from their universities or even funding agencies. Pepsico food scientists writing on behalf of Pepsico are not doing the same kind of science communication.

With more visible caveats, and maybe some sort of special treatment in the ScienceBlogs RSS feeds, Food Frontiers doesn’t have to be the end of all credibility for ScienceBlogs. But, boy, it doesn’t look good right now—and, if I’d spent a substantial portion of my blogging career helping to build ScienceBlogs into the hub of respectable online science writing it’s become, I’d be pretty upset. It looks like ScienceBlogs is losing some really strong writers over this, and that seems like a poor trade-off.

The only possible upside? The possibility we’ll get to hear PZ Meyers and Rebecca Skloot interviewed by Bob Garfield.

Losing the scientific lede, continued

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So, in spite of having pretty consciously tweaked the science blogging community when I wrote, in Monday’s post

Blog posts are best when they’re less than 700 or 800 words long, and their contents are readily summed up in a headline and only slightly expanded upon by the first paragraph. Think newspaper, not magazine articles. Do people read posts longer than that? Sure they do. But the longer a post is, the more possibility there is that some fraction of the readers will quit reading before the end, and maybe even pass on links or comments based on that incomplete understanding. I realize I’m not in the majority of online science writers in taking this position, but I think this better reflects how the average online reader reads.

I nevertheless managed to miss when Bora Zivkovic gently tweaked back over Twitter:

Do you agree? Losing the scientific lede: http://bit.ly/94zroM by @JBYoder compare: http://bit.ly/cJj3vs Long is fine.

But I did notice a larger-than-usual traffic spike associated with the post, and, being pretty sure of the source, I thought I’d just add to what I said previously, in light of the quite coherent and reasonable defense Bora makes for long-form posts.

In Bora’s older post, the point is not so much that blog posts should be long, but that blogs are a good venue for science communication because posts can be long:

Context – there is no space for context in a short article. Yet it is the context that is the most important part of science coverage, and of science itself – remember the “shoulders of giants”? Placing a new study within a historical, philosophical, theoretical and methodological context is the key to understanding what the paper is about and why it is important, especially for the lay audience. Even scientific papers all provide plenty of context in the Introduction portion (and often in the Discussion as well) which is sprinkled with references to earlier studies.

I strongly agree that context is important, and I also agree that blogs are great at providing context—but because a post can link to context, not necessarily provide it itself.

Much of my feelings about what a good blog post should look like are determined by two things, both of which are more aesthetic than empirically justifiable. Both are also related to my all-but-minoring in English as an undergraduate: I am a devoted follower of Strunk and White, and I wrote for the campus paper and took courses in newspaper writing. So I try to follow the inverted pyramid to some approximation, and when a post starts to spill below what displays in a browser window without scrolling down, much like this one, I start to worry that I’m not omitting needless words.

It’s my own online reading experience that short posts, which communicate a single scientific result, work better than longer posts trying to synthesize lots of different results. Again, that’s mostly an aesthetic judgment, but as I said in Monday’s post, I think that short posts are more likely to be read to the end, and less likely to result in distortions as a post propagates across social media (or, rather, only has the distortions I’ve introduced myself!).

Of course, maybe that’s a moot point. If a reader mischaracterizes my post in a Facebook update, but includes a link to it, everyone who clicks through will see that the post said something different. Right? Well, again, when they do click through, I suppose I’d like them to be able to take in the point of the post quickly, and understand what it actually says without needing to read all the way to the end.