Category Archives: science

Magpie, know thyself

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Photo by p_adermark.

New in PLoS Biology: European Magpies can recognize their own reflection in a mirror. Self-recognition in a mirror is used as a test of self-awareness in non-human animals, so this suggests that magpies, and maybe other birds, are conscious of themselves as separate from other members of their species.

To see if a magpie knew that a reflection in a mirror was an image of itself, the study’s authors glued a colored paper spot to the feathers below a magpie’s “chin”, then allowed the bird to see itself in a mirror. The magpie would have no way of seeing the spot except in the mirror, so if it reacted to the mirror image by trying to remove the mark from itself, it can be said to have recognized its own reflection. (And, presumably, thought something like “What the heck is this on my chin?”)

The supplementary materials for the paper include a number of videos of the test in action: here’s a magpie reaching for the mark with its foot [.wmv file], and here’s one using its beak [.wmv file]. Black spots, which wouldn’t be visible against the birds’ black chin-feathers, served as a control.

This is the first time that a non-mammal has been shown to be self-aware, and (in this one regard, anyway) it means magpies are smarter than monkeys. (Great apes recognize themselves in mirror tests; monkeys don’t.) It’s also more evidence that what we think of as consciousness, that nebulous quality that separates humans from the rest of the animal kingdom, isn’t as clear-cut as we used to think. Human intelligence most likely evolved by the incremental assembly of different mental skills – including self-awareness, but also tool use and language – that we see in other smart animals.

Reference

Helmut Prior, Ariane Schwarz, Onur Güntürkün, Frans de Waal (2008). Mirror-Induced Behavior in the Magpie (Pica pica): Evidence of Self-Recognition PLoS Biology, 6 (8) DOI: 10.1371/journal.pbio.0060202

Against specialist herbivores, plants give up

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Plants put up with a lot – everyone wants to eat them! And, basically, there are two ways a plant might respond to being eaten. They can put energy into regrowing bits that get eaten, or they can put energy into making a lot of some nasty chemical, like the milky sap in milkweed. The trouble with the first option is obvious – it doesn’t do anything to stop the damage. But the trouble with the second is that, whenever plants evolve a new defensive strategy, herbivores evolve a way around it. Often, these herbivores do very well, because they can eat something no one else can – and they become specialists on their new favorite food.


Photo by Melete.

Evolutionary ecologists have been thinking about this plant-herbivore arms race ever since Darwin. Back in 1964, Paul Erhlich and Peter Raven proposed that plants and insects might go through alternating cycles of diversification [$-a] driven by the evolution of new plant defenses and insect counterdefenses. Now, in a new paper in last week’s PNAS, Anurag A. Agrawal (who is at the top of everyone’s reference list) and Mark Fishbein show that sometimes, plants just throw in the towel [$-a].

Agrawal and Fishbein examine the evolutionary history of milkweed, which has a number of interesting anti-herbivore defenses besides the eponymous sap – and a number of specialized herbivores, like the red milkweed beetle pictured here. Their analysis looks for long-term evolutionary trends in the degree to which milkweeds put their energy into defenses, and the degree to which they put energy into regrowth. Over evolutionary time, it seems that milkweeds have reduced their defenses, and increased their regrowth efforts.

References

A. A. Agrawal, M. Fishbein (2008). Phylogenetic escalation and decline of plant defense strategies PNAS, 105 (29), 10057-10060 DOI: 10.1073/pnas.0802368105

P.R. Ehrlich, P.H. Raven (1964). Butterflies and plants: A study in coevolution Evolution, 18 (4), 586-608

Science as storytelling

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Photo from the Radiolab blog.

This week’s podcast from Radiolab is co-host Robert Krulwich’s commencement address to the class of 2008 at the California Institute of Technology. It’s a rousing call for scientists to put in the effort to talk about science to non-scientists, and how to use stories to do it. Because, says Krulwich, science is valuable:

But somewhere in that nightmare of work [leading up to graduation] you may have noticed that your teachers were giving you more than tension headaches. They were giving you values. A deep respect for curiosity. For doubt, always doubt. For open-mindedness. For going wherever the data leads, no matter how uncomfortable.

But that doesn’t do it justice. Go listen to the whole thing. Now.

“Evolution never takes a vacation”

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ResearchBlogging.org
This week’s column from Olivia Judson gives some examples of recent, rapid evolutionary change. She cites the evolutionary change seen in the beak size of Darwin’s finches [$-a], the flowering time of Californian field mustard [$-a], and the head shape and diet of Croatian wall lizards [$-a], but misses one of my favorite recent cases: the weed Crespis sancta.

This little plant recently moved into urban Montpelier, France, wherever its seeds land on cracks in the sidewalk or end up in patches of landscaping. And that urban landscape poses a problem for C. sancta – its seeds normally disperse like a dandelion’s, by floating on little feathery vanes. But if a plant is surrounded by pavement, most seeds that disperse this way will end up on pavement, unable to take root. So, as a recent study [$-a] shows, natural selection has favored a mutant C. sancta that doesn’t have vanes on its seeds. Vane-less seeds land right next to their parent plant, where there’s sure to be soil.

Of course, there are lots of instances of evolution in action that Judson hasn’t cataloged – because, as she rightly says, it’s going on everywhere, all the time: “Evolution never takes a vacation.”

References

P. R. Grant (2006). Evolution of Character Displacement in Darwin’s Finches Science, 313 (5784), 224-226 DOI: 10.1126/science.1128374

S. J. Franks, S. Sim, A. E. Weis (2007). Rapid evolution of flowering time by an annual plant in response to a climate fluctuation PNAS, 104 (4), 1278-1282 DOI: 10.1073/pnas.0608379104

A. Herrel, K. Huyghe, B. Vanhooydonck, T. Backeljau, K. Breugelmans, I. Grbac, R. Van Damme, D. J. Irschick (2008). Rapid large-scale evolutionary divergence in morphology and performance associated with exploitation of a different dietary resource PNAS, 105 (12), 4792-4795 DOI: 10.1073/pnas.0711998105

P.-O. Cheptou, O. Carrue, S. Rouifed, A. Cantarel (2008). Rapid evolution of seed dispersal in an urban environment in the weed Crepis sancta PNAS, 105 (10), 3796-3799 DOI: 10.1073/pnas.0708446105

Creationist research: Not just wrong – redundant, too!

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Virologist-blogger ERV takes down a Creationist study of bacterial antibiotic resistance, pointing out (1) the methods are flawed, (2) there’s no replication, (3) the interpretation is bogus, and – my personal favorite – (4) someone else has already done the same experiment:

Look, I know relatively little about bacteria. They arent the ‘micro’ in microbiology Im most interested in. But I can do a basic PubMed search to find a paper that analyzed the fitness cost of antibacterial resistance in Serratia marcescens the hard way (ie, the right way): A Fitness Cost Associated With the Antibiotic Resistance Enzyme SME-1 β-Lactamase. [hyperlink from original]

On the Media on Science 2.0: Sounds good to us!

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[Rant alert – I’m starting to get real tired of this nonsense. Although it is proving to be good blog fodder, and it got me published in the letters column of Science. Maybe it’s not so bad. And but so …]

Wired editor Chris Anderson is on this week’s On the Media, talking up the Petabyte Age. And OTM pretty much swallows it whole.


Photo by Pixelsior.

The Petabyte Age, as Anderson describes it, is the present time in which massive volumes of data (petabytes, in fact) are supposedly marking the end of the scientific method. If you actually read the Wired story, you’ll discover that Anderson has a pretty shaky grasp on what the scientific method actually is, and apparently thinks that “statistical analysis” is not hypothesis testing. As it turns out, it is.

On OTM interview, Anderson recants the sensationalist headline, possibly in response to the long string of critical comments it drew on Wired.com. But he repeats all of the mistakes and nonsense that generated the criticism: Craig Venter sequenced some seawater without a prior hypothesis, and Google summarizes lots of data to look for patterns without prior hypotheses; ipso facto, no one needs hypotheses anymore. (Anderson insists on talking about “theories” rather than hypotheses, which only highlights his unfamiliarity with basic philosophy of science.) The interviewer, Brooke Gladstone, pretty much lets him have his say. Does she then consult an actual working scientist, or, better yet, a philosopher of science? Not so much.

This is not the sort of coverage I’ve come to expect from OTM, which is basically in the running with RadioLab for the title of My Favorite Public Radio Show. Normally, OTM specializes in pointing out exactly this sort of failing in other news shows – interviewing pundits without actually talking to people who work in the fields in question. But it would seem that they don’t feel the scientific freaking method is important enough to cover properly.

Specialization: Not always a dead end

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Ruellia sp. – probably hummingbird specialized.
Photo by Tim Waters.

ResearchBlogging.org One of the big questions in evolutionary biology is about reversibility. That is, once an organism evolves down a path of adaptation to a particular climate or biological community, how easy is it for natural selection to make a U-turn and go back to a less specialized state? Many evolutionary changes are probably irreversible – an idea that was classically expressed in “Dollo’s Law”: “An organism is unable to return, even partially, to a previous stage already realized in the ranks of its ancestors.” But many evolutionary changes may not be irreversible – and it’s not always easy to predict which ones those are.


Ruellia brittoniana – probably bee-pollinated.
Photo by petrichor.

A new study in this month’s issue of Evolution aims to answer this question [$-a] for a group of flowers in the genus Ruellia. The authors, Tripp and Manos, use a phylogeny to reconstruct the evolutionary history of pollination syndromes, groups of floral traits like color, nectar tube length, scent, &c, that are associated with pollination by different groups of animals.

For instance, bright red flowers with longish, narrow nectar tubes, not much scent, and large volumes of dilute nectar (like the Ruellia species in the upper figure), are almost always pollinated by hummingbirds; blue flowers with short nectar tubes, stronger scent, and small volumes of concentrated nectar (like Ruellia brittoniana in the lower figure) tend to be pollinated by bees or other insects. Other Ruellia species are pollinated by hawkmoths (white flowers, very long nectar tubes) or bats (yellow flowers, short nectar tubes, lots of dilute nectar, strong scent). Generally, syndromes associated with a single, small group of pollinators (hummingbirds, hawkmoths, or bats) are considered “specialized”, while syndromes associated with many more different pollinators (bees and insects) are not.

With a phylogeny of the genus Ruellia, Tripp and Manos use the pollination syndromes of currently existing Ruellia species to estimate what pollination syndromes their ancestors may have had. Then they determine how common transitions between pollination syndromes have been in the history of Ruellia, and whether any pollination syndromes are “dead ends” – that is, whether Ruellia species that evolve to specialize on, say, hummingbird pollination are “stuck” that way.

Surprisingly, Tripp and Manos found that some specialized pollination syndromes are dead ends, but one, the hummingbird syndrome, isn’t. Hawkmoth- and bat-pollinated species tended to have evolved from ancestors with the bee/insect syndrome, and they seem to be “stuck” once they get there. But in several cases, hummingbird-specialized ancestors have given rise to bee/insect-pollinated species. This has never been seen before in other, similar groups of plants. Hummingbirds are generally thought to be more efficient pollinators than bees, so while it makes sense for flowers to evolve from using bees to using birds, it’s not clear how natural selection would work in the opposite direction.

Reference
Tripp, E.A., Manos, P.S. (2008). Is Floral Specialization an Evolutionary Dead-End? Pollination System Transitions in Ruellia (Acanthaceae). Evolution, 62(7), 1712-1737. DOI: 10.1111/j.1558-5646.2008.00398.x

Chameleons change color to communicate

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That’s right. Chameleons don’t change color to hide; they do it to assert social status and otherwise communicate with each other. How do we know this? By working out how chameleons look to other chameleons and their predators. Full story, with refs, at dechronization.

A new plan for links

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I post about science quite a bit, and when I do, I try to link to the “primary” literature – peer-reviewed research articles in professional journals. But even in this modern age, lots of professional journals charge for access. Sometimes a lot. I get through on my university’s institutional subscription – but that doesn’t cover everyone. So I’ve been trying to mark links to journal articles based on whether it’ll cost you to read the full text, but I haven’t been happy with the way it looks. Therefore, I’m instituting a set of simple abbreviations, which I’ll append to linked text to indicate access levels:

  • [$$] = total lockdown; nothing but the title is free online
  • [$-a] = the article’s abstract is free, but more will cost you
  • No mark = totally free access

Check out an example of how this looks in a post. Links to an article at PLoS, which is fully open-source, aren’t marked. But links to an article at Science get the [$-a] mark. Links to article titles in the “References” section at the end aren’t marked one way or the other – I sort of assume those don’t get the same kind of follow-through that the in-text links do.

Climate change: bad for native plants

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[Correction/clarification appended]

This is how I can justify blogging as a scientific activity: once in a while, I find something really useful. Case in point is this post on the ‘blog of Pamela Ronald, the chair of the University of California Davis plant genomics program, which points to a new in the last volume of PLoS ONE that predicts (perhaps not surprisingly) climate change is going to be bad for rare plants in California.

The effect of climate change on plant communities is a major concern for me, because the range of my favorite woody monocot, the Joshua tree, may have to change quite a bit to compensate for a warmer climate. (For reference, see the photo of me setting up a pollination experiment on a Joshua tree in front of the Yucca Valley United Methodist church.) Previous projections have suggested that Joshua trees are going to be in trouble under a warming climate. Back in 2006, Science ran a cover article suggesting that climate change may make wildfires more frequent [$-a]. That’s a very real problem for Joshua tree’s range in the Mojave Desert – my lab has already lost field sites to brush fires in only about half a dozen years of focusing on Joshua trees. Another, more recent study has suggested that climate change is going to make the southwest U.S. even more arid&nbsp[$-a], which is also, obviously, a bad thing for plants (and people) in the region.

Earlier work of this sort usually modeled how climate change might increase or decrease the distribution of individual plant species – big, showy things like Joshua tree, Saguaro cactus, giant Sequoias. Loarie et al. improve over this by projecting changes in whole plant communities across the California floristic province. And they predict that up to 66% of plants endemic to California will lose more than 80% of their ranges. That’s a lot of diversity – more than just my study organism – at stake.

Correction:
In the original version of this post, I conflated the state of California, which does include a lot of Joshua tree’s range, with the California floristic province, which doesn’t. So Loarie et al.‘s new paper doesn’t directly impact Joshua trees. But it’s still cool/alarming, and decidedly post-worthy. In making that correction, I’ve also inserted a more recent study of climate change in the U.S. southwest, by Seager et al.

References:
Loarie SR, BE Carter, K Hayhoe, S McMahon, R Moe, CA Knight, and DD Ackerly. 2008. Climate change and the future of California’s endemic flora. PLoS ONE 3:e2502.

Seager R, M Ting, I Held, Y Kushner, J Lu, G Vecchi, H-P Huang, N Harnik, A Leetmaa, N-C Lau, C Li, J Velez, and N Naik. 2007. Model projections of an imminent transition to a more arid climate in southwestern North America. Science 316:1181-4.

Westerling AL, HG Hidalgo, DR Cayan, and TW Swetnam. 2006. Warming and earlier spring increase western U.S. forest wildfire activity. Science 313:940-3.