Good to the last dropping: pitcher plant evolves to be shrew loo

March 12, 2010 • 8:28 am

We evolutionary biologists have one advantage over other biologists: we’re constantly encountering bizarre features of nature showing the almost unbelievable variety of adaptations that can be produced by natural selection.  This means that we’re constantly getting little frissons of pleasure, and I get at least one of these a month.  The most recent came from a new paper in New Phytologist by Chin et al. These authors make a pretty compelling case that the morphology of three species of pitcher plants in Borneo has evolved to not only catch the droppings of tree shews (and use them as nutrients), but to compel the shrews to defecate (and probably urinate) in their pitchers.  In other words, they’ve evolved to be shrew toilets.

Working on Mount Kinabalu in Borneo, Lee et al. discovered that three species of pitcher plants in the genus Nepenthes (N. lowii, N. macrophylla, and N. rajah, the world’s largest carnivorous plant, shown in Fig. 2), have evolved features that make them attractive to treeshrews of the genus Tupaia.  (Treeshrews are neither rodents nor shrews; they’re a group more closely related to primates than to rodents). The plants have recurved “lids” that produce a sweet substance that the tree shews lap up while sitting astride the pitchers.

The authors found that, depending on the species of plant, between 60% and 90% of the pitchers contained fecal pellets from treeshrews.  Video cameras placed near pitchers of N. rajah captured 7 treeshrew visits, lasting an average of 24 seconds, and one of these showed the beast crapping into the pitcher. Previous analysis (Clarke et al. 2009) showed that these pellets provide a large fraction (58-90%) of the nitrogen needed by N lowii.

Geometric analysis of the three feces-trapping species showed that the leaf morphology has evolved in such a way that forces the shrews to sit astride the plant while eating its exudate (Fig. 2). The three species in which feces were observed all have a combination of lid angle, lid concavity, and pitcher width that forces the shrews (given their body size, which was also measured) to straddle the plant if it wants access to the entire lid surface.  Other species, and pitchers of immature plants in the three “target” species, don’t have this combination of traits, and although treeshrews will sometimes lick their lids, they don’t defecate in them.

Figure 1 (from Chin et al.)  The senior author measuring a pitcher of N. macrophylla.  Bar is 5 cm (about 2 inches).

Figure 2 (from Chin et al.). Images from videocam recordings of N. rajah pitchers.  Left:  T. montana stradding a pitcher and eating its secretions.  Note the animal’s butt inside the pitcher.  Right: treeshrew feces in a pitcher.  Scale: 5 cm.

Now this coincidence between treeshrew size and plant geometry may be a coincidence rather than an adaptation, but it’s a good guess that, given the frequency of fecal-pellet deposition in the pitchers and the important contribution they make to the plant’s acquisition of nitrogen, as well as the fact that the three species of pellet-using pitchers are evolutionary outliers among Nepenthes in their large size and lid configuration, the pitchers have evolved to be shrew loos. In the earlier paper by Clarke et al., the authors posit that, because some treeshrews scent mark the plants by urinating on them, the pitchers could also be using this urine.

The authors describe the whole situation as “an extraordinary example of co-evolution and specialization” but I reserve the the term “co-evolution” for cases, like figs and their fig-wasp pollinators, in which both species have evolved because of their interactions. In this case there’s no evidence that treeshrews have themselves undergone any evolutionary change since they started using pitcher plants, although this is possible.  The shrews, for example, could have a genetically based propensity to seek out pitcher plants. But we don’t know if this is the case.

Fig. 3.  I can haz privacy? A mountain treeshrew doing its business on a pitcher.  Photograph by Ch’ien C. Lee.

Pitcher plants are a remarkable example of convergent evolution: the evolutionary modification of leaves into pitchers that trap insects or other nutrient-providing stuff has occurred three times in three independent groups, the Sarraceniaceae (North and South America), the Nepenthaceae (tropical Asia), and the Cephalotaceae (Australia).

And, finally, there’s one species of ant, Campanotus schmitzi, that dives into the pitcher-plant liquid and retrieves drowned insects as well as living mosquito larvae.  These ants can actually swim, remaining submerged for up to 30 seconds! The authors note that it can then take an ant up to 12 hours to haul its prey out of the fluid and up to the pitcher mouth.

Clarke and Kitching (1995), the authors of the study, suggest that this is a mutualism between ant and plant since the ants prevent too many arthropods from accumulating and putrifying inside the pitcher—something that disrupts the plant’s ability to digest them.

h/t: Matthew “Swammerdam” Cobb

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Chin, L., J. A. Moran, and C. Clarke.  2010.  Trap geometry in the giant montane pitcher plant species from Borneo is a function of tree shrew body size. New Phytologist, in press (early view).

Clarke,  C. M. and R. L. Kitching. 1995.  Swimming ants and pitcher plants: a unique ant-plant interaction from Borneo.  J. Tropical Ecology 11:589-602.

Clarke, C. M., U. Bauer, C. C. Lee, A. A. Tuen, K. Rembold, and J. A. Moran. 2009. Tree shrew lavatories: a novel nitrogen sequestration strategy in a tropical pitcher plant. Biology Letters 5:632-635.

Michael Ruse’s new book

March 11, 2010 • 11:55 am

I swear, Michael Ruse is like your befuddled old uncle who behaves nicely most of the time, but then, in the middle of Thanksgiving dinner, says something like, “Oops, I wet myself!”  In matters like his recent attack on evolution-denying philosophers, he’s right on the mark.  But then he goes and has an accident, like the appearance, three days ago, of his new book Science and Spirituality.   I haven’t read it yet, and won’t unless somebody pays me to review it, but it sounds like The Faitheist Manifesto.  Here’s its description on Amazon:

In Science and Spirituality: Making Room for Faith in the Age of Science, Michael Ruse offers a new analysis of the often troubled relationship between science and religion. Arguing against both extremes – in one corner, the New Atheists; in the other, the Creationists and their offspring the Intelligent Designers – he asserts that science is undoubtedly the highest and most fruitful source of human inquiry. Yet, by its very nature and its deep reliance on metaphor, science restricts itself and is unable to answer basic, significant, and potent questions about the meaning of the universe and humankind’s place within it: Why is there something rather than nothing? What is the ultimate source and foundation of morality? What is the nature of consciousness? What is the meaning of it all? Ruse shows that one can legitimately be a skeptic about all of these questions, and yet why it is open for a Christian, or member of any faith, to offer answers. Scientists, he concludes, should be proud of their achievements but modest about their scope. Christians should be confident of their mission but respectful of the successes of science.

Yes, of course religions are permitted to answer questions like, “What is the nature of consciousness?”  But there’s no way to determine whether their answers are right.

Jesus and Mo cartoon h/t to: Far away

“So what do you do for a living?”

March 11, 2010 • 9:51 am

Related by Matthew Cobb:

In the Times Literary Supplement today (not on the website) there’s a review—by D. D. Guttenplan of The Nation—of Jonathan Wittenberg’s new book, The Silence of Dark Water. Wittenberg is a rabbi from the Masorti, and so is an arch-accommodationist from the other side. However, he has a good joke.  Wittenberg was at Loch Ness on holiday and was appalled by all the tourist trash: t shirts, pens etc.

Wittenberg tells the joke on himself: ” ‘So much stuff and no one’s even seen the creature!’ I complained. ‘So what do you do for a living?’ came the reply.”

Black penguin!!!

March 11, 2010 • 6:26 am

. . . or, as we biologists say, a melanistic penguin—a king penguin (Aptenodytes patagonicus), to be precise.  I’m reporting on this because I’ve been a bit of a penguin freak ever since I wrote a biology term paper on these birds in 1964, and, let’s face it, who doesn’t love penguins?

Now you’re gonna cry “Photoshop” or “hair dye” on this one, but as far as I can tell it’s real.  The National Geographic blog Intelligent Travel reports on and shows (Fig. 1) a black penguin just seen by writer Andrew Evans on the island of South Georgia (South Georgia is, of course, the island Ernest Shackleton crossed on foot in 1916 to seek rescue of his men during the disasterous Imperial Transarctic Expedition of 1915-1917).

Figure 1.  The black king penguin (from Intelligent Travel)

Evans reports the sighting:

He looked like a single black king moving across a chessboard of so many white pawns. Our first glimpse was puzzling until we drew closer and realized that this was not some other bird but indeed another penguin of a different color.

Our group from Lindblad Expeditions spotted this very unique bird at Fortuna Bay on the subantarctic island of South Georgia. Out of several thousand pairs of king penguins, this was the only individual that was entirely black although earlier in the morning I had spotted another that showed muted coloration. Recent science papers (PDF) show that the trait has been documented only a handful of times in South Georgia. Some fellow travelers recall seeing a melanistic penguin at St. Andrew’s Bay, also on South Georgia.

Dr. Allen Baker, a Canadian ornithologist who’s published on melanistic birds, describes his reaction to the photo with scientific precision:

“Well that is astonishing,” he said. “I’ve never ever seen that before. It’s a one in a zillion kind of mutation somewhere. The animal has lost control of its pigmentation patterns. Presumably it’s some kind of mutation.”

Intelligent Travel also reports an independent sighting of a melanistic king penguin on South Georgia in 2006 by Ted Cheeseman and members of his ecology expedition.  The bird, presumably the same individual, was photographed by Hugh Rose (Fig. 2).

Fig. 2.  The black king penguin (presumably the same individual) photographed in 2006.

The paper mentioned in Intelligent Travel, by Louise Blight and Sylvia Stevens, reported a partially black king penguin on South Georgia in 2000 (Fig. 3; only the ventral surface was abnormally colored).  This may be the same individual as the one spotted by Evans and Cheeseman. Sadly, Blight and Stevens note that the individual “did not appear to be breeding.”  I worry that its abnormal coloration will make it unsuitable as a mate.  Blight and Stevens also report two other partially melanic king penguins; Figure 3 also shows one of these.


Fig. 3.  Photos from the Blight and Stevens paper.  Left: melanistic king penguin seen on South Georgia in 2000. Right: king penguin with partial melanism on breast (seen on Isle Crozet).

Blight and Stevens report that melanism has also been seen in the Adelie, Royal, gentoo, and chinstrap penguins, while the absence of pigment (leucism) has been seen in seven species of penguins (there are 17 species of the bird in toto).

Melanism is often (but not always) the result of a single gene mutation.  Melanistic mutations are responsible for producing dark jaguars and leopards, called “black panthers” (Fig. 4) and erroneously assumed to be a different species from nonmelanistic individuals.

Some of the commenters at the Intelligent Travel site assert that this picture is Photoshopped.  Seeing the earlier pictures and reading about the independent sighting in 2006, I’m fairly sure it’s real.

Fig. 4.  A melanistic jaguar (“black panther”), Panthera onca

h/t: Steven Mears

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Blight, L. K. and S. Stevens.  2000. Partial melanism in King Penguins Aptenodytes patagonicus.  Marine Ornithology 28:83.

Radio bit on home-schooling, and more angry emails

March 10, 2010 • 9:17 am

The kerfuffle about home-schooling and evolution led to an invitation for me to do a brief segment on Overnight America with Jon Grayson.  You can find that segment here.

I continue to get angry emails from home-schooling parents. Many of them are really exercised by my statement that the Apologia and Bob Jones biology home-school units are “promulgating lies to kids.”  I can see how a parent would get upset at the accusation that he/she is lying to their kids, but what I said was that the books are promulgating lies to kids.  And they are—the publishers should know better.  But if the creationism-pushing parents have had an opportunity to know better, by learning something about the evolution they teach (or don’t teach) to their kids, then they too are guilty of promulgating lies.  It’s as simple as that, because evolution is true.

Let me add, though, that I’ve received a (very) few supportive emails from home-school parents.  It need hardly be said that these folks are home-schooling their kids for other than religious reasons.

Here’s an email that came only half an hour ago:

Professor Coyne,

“I feel fairly strongly about this. These books are promulgating lies to kids,” said Jerry Coyne, an ecology and evolution professor at the University of Chicago.

Uh, no they don’t. But you do. It seems to be part of your job description.

The home schooling movement arose because people were sick of outsiders having a dominant role in what parents teach their own children. What the “experts” think is more important than what the parents think.

Maybe in a few years, when a number of smart home-schooled kids graduate (and they are smart!), they can finally have a debate with the public school kids who were taught evolution. As it stands now, a debate is impossible, as all kids are taught one thing (evolution) as an article faith. Yes, an article of FAITH. As your unscientific attitude suggests, questioning the theory is not welcomed.

Please mind your business and don’t worry yourself with public school refugees and what they choose to teach their children.

and another:

Here is a quote I read from you in an article entitled, “Top Homeschool Texts Dismiss Dawin” by the Associated Press. “I feel fairly strongly about this. These books are promulgating lies to kids,” said Jerry Coyne, an ecology and evolution professor at the University of Chicago .

And you also said, “If this is the way kids are home-schooled then they’re being shortchanged, both rationally and in terms of biology,” Coyne said.

I think you’re extremely ignorant of homeschoolers in general. We choose what we choose for our children because it’s our right. You, as a college professor choose what you choose for your students because it’s your right. It’s laughable that you would even state such a hyberole that Christian publishers are “promulgating lies”. They’re CHRISTIAN publishers. What else do you expect them to teach? I am not even going to address the lies and fallacies in evolution, the simplest one being that we came from animals.

I think government run schools are shortchanging children because they are being taught that we are nothing more than animals. That’s a sad state of affairs. It would depress my children to no end if they even thought they were evolved from an animal. And our children probably know a lot more about evolution than the average government run school child does anyway.

Darwinists don’t know everything. And you particularly don’t know much about Darwin either if you are teaching his “theory” as fact.

I feel sorry for you because you have no imagination or wonder in your thought or process. God created us in His image. He has a plan for us and regardless of what you or I think about the Bible and His Word it doesn’t change what He says. That’s the amazingly glorious thing about the Bible. Darwin’s theory has “evolved” over the last few hundred years but God’s Word has been the same since He said, “In the Beginning” 6,000 years ago.

One more:

“I feel fairly strongly about this. These books are promulgating lies to kids,” said Jerry Coyne, an ecology and evolution professor at the University of Chicago.

I am certain you remember the quote stated above.  With all due respect, I find your comment to be insulting and dangerous.  You are a respected member of the scientific community; and for you to indicate that books teaching creation as opposed to evolution is “promulgating lies to kids” implies that you know for certain that evolution is not a theory but a law.  I am sure you know that the THEORY of evolution is not yet proven, and I will boldly state that you will never PROVE the theory.  Your statement can be used by less knowledgeable members of the society (include politicians) as a defense or justification to outlaw creation, religion, and home schooling.  Although I will never be able to PROVE creation to you, I am certain a scientific mind can see intelligent design in our universe and in life itself.  The scientific community cannot have both entropy and evolution; they are mutually exclusive.  By the way, I am sure you know the 2nd LAW of thermodynamics (not 2nd THEORY of thermodynamics).  I am not writing this to convert you to Christianity or even to have you accept creation and reject evolution (nor will anything you can quickly state in an email be able to change my mind to accept evolution).  My purpose is to ask you to keep an open mind about the subject, just because it is contrary to a theory you hold true does not make it a lie.  Realize that making bold statements that are impossible for you to prove can only hurt our society.  You have a responsibility to speak only the KNOWN truth, qualify statements of opinion or theory and to keep your agenda outside of the public realm.  To those that believe creation is the truth, your text books promulgate lies.  I believe it is important to teach both theories and allow the student to determine which they will consider as more plausible.  Educators are to teach what is known and to qualify any statement that is not known but is believed or theorized.

The common thread of many of the emails I’ve received is that evolution is not “proven”:  that it’s not a fact but a theory.  I have tried to instruct one or two of these correspondents in what a scientific theory really is, and in the  idea that the “theory” of evolution is just as much a fact as is the “germ theory” of disease.  But, as you might guess from the threads of the past few days, such instruction is futile.

I weep for the children who are home-schooled in creationist lies instead of science.

A new guide to The Origin

March 10, 2010 • 7:23 am

There’s a spate of books out for Darwin Year (including mine!), but you may be asking yourself, “Should I bite the bullet and read On the Origin of Species” itself?  The answer, of course, is YES.  This is the one scientific book that you must have read if you consider yourself at all educated.  Yes, sometimes it’s hard going, even for an evolutionary biologist (the chapter on “hybridism” is a toughie), and yes, the Victorian prose is sometimes ponderous to modern ears.  But all is trumped by the sheer power and beauty of Darwin’s arguments.  And sometimes the prose is lovely: a famous example is the last paragraph.  The metaphor of the tangled bank, and the phrases “this view of life” and “endless forms most beautiful” have been coopted in the titles of innumerable books and articles by biologists (and should now be gracefully retired):

It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us. These laws, taken in the largest sense, being Growth with Reproduction; inheritance which is almost implied by reproduction; Variability from the indirect and direct action of the external conditions of life, and from use and disuse; a Ratio of Increase so high as to lead to a Struggle for Life, and as a consequence to Natural Selection, entailing Divergence of Character and the Extinction of less-improved forms. Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved

There are guides to help you not only appreciate what Darwin is saying, but also to put his contributions in the context of modern evolutionary biology.  If I were teaching a seminar on The Origin to biology students—something I may well do next year—I would use two books.  I’ve already mentioned the first in an earlier post: The Annotated Origin by James Costa, a facsimile of Darwin’s first edition, garnished with copious marginal notes and explanations.  You can download some sample pages at the book’s website.

The second would be a book that was published last September, and has just landed in my mailbox: The Origin Then and Now: An Interpretive Guide to the Origin of Species, by David Reznick of the University of California, Riverside.  This 432-page book, published by Princeton University Press, takes The Origin chapter by chapter, explaining what Darwin is saying (interpreting it in light of modern biology) and discussing how Darwin’s ideas have fared since 1859.

Reznick’s chapters have a one-to-one correspondence with those of The Origin, and are divided into three broad sections: natural selection, speciation, and theory.  At the end of each section Reznick contributes an essay on the relationship of Darwin’s ideas to modern work on evolution (for example, the recent discovery of incipient species of mosquito living in the London Undergound).

With these two books under your belt, you’ll know more about The Origin than do many biologists. It’s surprising, actually, how many evolutionary biologists have never read the book.

Darwin’s “theory” of evolution is one of humanity’s supreme achievements, for it tells the true story of our origins, and by “our” I mean all living species. We are the only species that has figured out where we came from.  You owe it to yourself to read The Origin.

Another person finds God in quantum mechanics

March 9, 2010 • 3:10 pm

First Kenneth Miller, now physicist Paul Davies from Arizona State University.  On Krista Tippett’s NPR program, Speaking of Faith (transcript here), Davies struggles hard to reconcile God with science.  And where does he find our Elusive Lord?  In the supposedly upredictability of quantum-mechanical phenomena, of course!

Mr. Davies: Yes, there has always been this problem for physicists about an active God. If God does anything, God has to be at work in the world. And now, if we go back to the sort of universe that Newton had and the one that Einstein supported, the notion of a deterministic universe, a clockwork universe, then this becomes a real problem, because if God is to change anything, then God has to overrule God’s own laws, and that doesn’t look a very edifying prospect theologically or scientifically. It’s horrible on both accounts.

But when one gets to an indeterministic universe, if you allow quantum physics, then there is some sort of lassitude in the operation of these laws. There are interstices having to do with quantum certainty into which, if you want, you could insert the hand of God. So, for example, if we think of a typical quantum process as being like the roll of a die — you know, “God does not play dice,” Einstein said — well, it seems that, you know, God does play dice. Then the question is, you know, if God could load the quantum dice, this is one way of influencing what happens in the world, working through these quantum uncertainties. Now, some people certainly have pushed that idea. John Polkinghorne is one who’s spoken about it. Bob Russell for the Center for Theology and Natural Sciences in Berkeley likes that point of view of God not in any sense usurping the laws of physics, but working within the inherent lassitude that quantum physics provides. And it’s a possible way of God to gain cause or purchase in the world without changing any of the laws that we know.

Sometimes I wonder, when I hear stuff like this, if the people who say it really believe it, or if they’re only trying to reassure the nervous faithful that science really does allow for a theistic God.  Don’t they ever wonder why God would choose to work this way, rather than just acting more macroscopically?  Has the thought never crossed their minds that they’re making a virtue of necessity—indeed, playing a slightly more sophisticated god-of-the-gaps gambit?

And what if, some day, quantum “uncertainties” are shown not to be uncertain at all, but part of a deterministic process that we don’t yet understand?  Where would God go then? How could He continue to influence the universe?

After I read this, I had a thought.  I Googled “Paul Davies Templeton”.  Sure enough, Davies won the lucrative Templeton Prize in 1995.

Over at Rationally Speaking, Massimo Pigliucci dissects this nonsense in more detail.