Why Evolution is True is a blog written by Jerry Coyne, centered on evolution and biology but also dealing with diverse topics like politics, culture, and cats.
The statue of Carl von Linné, located on the Midway, has been spray painted with several phrases, including “death 2 amerikkka” and “death 2 academy.” The Midway is part of the Chicago Park District and the statue is not on University property.
– Nathaniel Rodwell-Simon, News Reporter
Now we can’t be sure that the protestors encamped here defaced this statue, but I haven’t seen it defaced in the 38 years I’ve been here. And the correlation with The Encampment, as well as the message, is striking. Defacing it makes no statement except “I am ignorant and hateful.”
If you don’t know who Linnaeus was (also called Carl von Linné after he became a nobleman), you can read about him here. He was a Swedish botanist and formulated the system of Latin binomials to identify organisms. (I visited his house, which still stands, when I lectured at Uppsala, but don’t have time to post the pictures.) He was amazingly productive, widely admired, and is known as “the Father of Modern Taxonomy.” Why some chowderhead would deface his statue defies me.
Here’s the lovely statue from the front, which I always admire when I walk by it on the Midway. It was created by Frithiof Kjellberg in 1891, installed the same year, and then relocated in 1976. And what a great thought to memorialize a famous biologist whom almost nobody has heard of!
Photographed by Joe Lothan, licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.
A science paper at last! Truth be told, I don’t come across many science papers that are both of general interest and that I can explain easily. But I do have several more in the queue.
A colleague sent me an old paper (from 2006), but its age does not diminish how spectacular the results are. And in short, the results are these: a group of 15 phenotypically similar (but probably not closely related) orchids in SW South Africa are pollinated by females of a single species of bee, which collects oil produced by the flowers and feeds it to their offspring.
This poses a problem, because orchids are pollinated by affixing sticky pollinia (sacs of pollen) collected from a flower of one species to the next flower of the same species. (The orchids in this group do not self-fertilize). With pollen sacs from 15 different orchid species sticking to a bee, how can a plant be sure that its own pollen gets transferred to another individual of the same species, rather than to another individual of a different species, in which case cross-species pollination would produce either inviable or maladapted hybrids?
The bees and orchids have solved this in a very clever way.
But let’s back up: the paper, from the American Journal of Botany, can be seen for free by clicking on the screenshot below, and the pdf is here.
The reason the author, Anton Pauw, gives for his 8-year investigation is that, he says, the “conventional wisdom” in botany is that it’s not adaptive for a bunch of flowers to depend on a single species of pollinator. That’s because if some environmental fluctuation or other contingency makes the pollinator rare (or even drives it extinct), the flowers wouldn’t get pollinated. This would imply that flowers should evolve to attract several species of pollinator, for those flowers that are generalists in this way are less likely to become rare or extinct themselves.
But this doesn’t seem to be the case in this group of 15 orchids, which, according to Pauw’s observation, come from three different genera (molecular phylogeny also suggests that they’re not each other’s closest relatives, though they look remarkably similar). Yet all are pollinated by a single bee, Rediviva peringueyi. This is in a genus called “long-legged oil bees.”
The flowers, as I said, look like each other, all produce oil that the bee collects, and all live in the same area, as well as flowering at the same time. As the author says,
Subgroups of similar plant species can be recognized within the extensive oil-bee pollination system. The one examined here includes 15 oil-secreting orchids that share the following syndrome of floral features: pale yellow-green flowers without extensive black markings; secretion of floral oil as a pollinator reward; characteristic pungent scent; flowering period 15 August to 25 October peaking in September; flower depth 5–8 mm (Fig. 1a–n). The species occur in close association with one another in the lowlands of the Cape Floral Region and include members of three genera (Pterygodium, Corycium, and Disperis). According to the pollination syndrome concept, the similar floral features of this group indicate a shared pollinator. My aim was to test this prediction through extensive field work.
Figure 1 below (click to enlarge; caption from paper) shows how similar the flowers are. The pollinating bee (R. poeringueyi, which I’ll henceforth call “the bee”) is shown in the middle. The arrows show where the pollinia of each orchid species gets attached:
Figure 1. The Rediviva peringueyi pollination guild. Center, the oil-collecting bee R. peringueyi, arrows indicate pollinarium attachment sites of orchid species. (a) Pterygodium catholicum. (b) P. alatum. (c) P. caffrum. (d) P. volucris. (e) Corycium orobanchoides. (f) Disperis bolusiana subsp. bolusiana. (g) D. villosa. (h) D. cucullata. (i) D. circumflexa subsp. circumflexa. (j) P. inversum. (k) P. hallii. (l) P. platypetalum. (m) D. ×duckittiae. (n) P. cruciferum. (o) D. capensis var. capensis. Attachment sites f–i after Steiner. Pollinarium attachment sites are confirmed in a–g. Pollination and/or pollinarium attachment are predicted in h–o on the basis of floral features. R. peringueyi 5× life size, orchids 2× life size. Images e, h, k by Bill Liltved.
The bees also collect pollen and nectar, too, but not from these orchids. From these 15 orchids they take only flower oil (I had no idea it even existed), and do so by, as you can see in the photo below, gripping the plant with the bee’s middle and hindlegs and collecting the oil with modified forelegs. In the process (and of course this is why the flower produces oil and scent to attract the bee). During oil collection, the pollinia of the orchid, which is sticky, attaches to the bee’s body. That’s also shown in the photo below.
This, of course, raises the problem noted above. If a pollen sac from one of the 15 orchid species is stuck to the bee’s body, how can it be guaranteed to pollinate the same species of orchid, for there’s no guarantee that the next flower the bee visits will be from the same species. (All the orchids are, after all, flowering at the same time.)
The answer is the cool part of the story. Each orchid has evolved to stick its pollen to a different part of the bee’s body. And each orchid has its female parts placed so that the pollinia from its own species, stuck to a specific place on the bee’s body, will contact it’s own species-specific style (the female bit that gets the pollen for fertilization). Thus cross-pollination is prevented by the specificity of where the pollinia stick to the bee and bu the specific position of the female part of each orchid, which has evolved so, that when the bee collects oil, the right pollen will land on the right stigma.
Paux found this out by identifying the different pollina of the flowers (they have different shapes), and trapping wild bees to see where the pollinia of each species was stuck to the body. That’s what’s shown in the figure above: each letter corresponds to the orchids depicted around the edges, and the arrows show where on the bee’s body the pollinia from each species are stuck. Notice that they’re all different. Except for two, that is: the pollinia from orchids b and c, which both stick to the foretarsi of the bee’s middle legs.
Does this mean there’s cross-pollination between orchids b and c, which would be bad? No, because the pollinia of these two species are of different length, and the stigmas of the two orchids are placed so that each will get the pollen from the right species.
This is a remarkable example of specificity in pollen placement; I know of nothing similar! You can see below, in “b” and “c” of Fig. 3, that the pollen are stuck to very specific parts of the body. In “b”, the pollen of the flower Pterogodium cathlocium get attached to the bee’s “basistarsi” on the middle legs (the most distal part of the large leg tarsi), while the pollinia of the orchid Pterygodium volucris get attached to the ventral surface of the bee’s abdomen. The pollen sacs on the flowers have to be in very different places to accomplish this, and the bee has to collect oil in a specific position to get the pollinia stuck to the right spot.
(From paper): Fig. 3. Rediviva peringueyi pollination mechanism. (a) Female R. peringueyi collecting floral oil from the apex of the lip appendage of Pterygodium alatum with a rapid rubbing motion of the front tarsi. The bee hangs onto the lip appendage with the middle tarsi, onto which the pollinaria (visible) become attached. Bar: 3 mm. (b) Several pollinaria of P. catholicum attached precisely to the basitarsi of the middle legs of R. peringueyivia the sticky viscidia. Bar: 1 mm. (c) Pollinaria of Pterygodium volucris attached to the ventral surface of the last abdominal segment of R. peringueyi. Bar: 3 mm.
Note that several types of evolution appear to be involved in this phenomenon:
a.) Convergent evolution of the different, unrelated orchids so that they develop a common scent, appearance, and “lip” that allows the bees to hang on while collecting oil.
b.) Divergent evolution of the orchids so that each evolves a lip and pollinia position that will stick its pollen to a previously uncolonized part of the bee’s body
c.) Possible evolution of the bee’s behavior so that it “knows” how to hold onto each species of flower to collect oil (this might not involve genetic evolution, but simply be due to learning).
So this is the cool way that fifteen different species of orchids can pollinate members of their own species, even if they’re all serviced by the same species of pollinator. According to Pauw, though, this doesn’t solve the problem raised at the beginning: such specificity makes the whole system precarious—liable to collapse if anything happens to the pollinator. And indeed, he says that the degree of pollination of the orchid species vary strongly from year to year. So it goes.
Another aspect of this system is the possible extinction of the bee. In a sad ending, Pauw notes that the habitat for both orchid and bee is disappearing:
The biggest challenge in this study was the scarcity of suitable study sites. About 80% of lowland vegetation has already been transformed by urbanization and agriculture (Heijnis et al., 1999). What remains are scattered fragments of natural habitat, mostly less than 1 ha in size. In many of these fragments, the absence of R. peringueyi and repeated pollination failure in the entire guild was recorded. We have probably already lost the chance to understand the intriguing flowers of species such as P. cruciferum, which persists in fewer than five remnants of natural vegetation where they seldom, if ever, receive pollinator visits. In contrast with the pollination systems of the north temperate regions, which almost invariably involve several ecologically equivalent pollinator species (Waser et al., 1996; Fenster et al., 2004), the pollination system described here is dependent on a single insect species. This presents a challenge for conservation because of the low level of ecological redundancy means that the loss of R. peringueyi may trigger linked extinctions amongst the plants in the R. peringueyi pollination guild. It seems unlikely that the R. peringueyi pollination guild will persist in a modern, cultural landscape without unique conservation planning.
If the bee goes extinct, so will every one of these orchid species, for their reproduction depends on the insects. There’s a lot more to study here, and I’m hoping that they’re trying to save some habitat for both plant and insect. Since pollination itself has been observed in only about five of these orchids, there’s a lot more observational work to be done. Further, the DNA analysis of the orchids, indicating that they are not a “monophyletic group” (i.e., not each other’s closest relatives) was rather crude, and that needs to be done using more modern methods. If they are not each other’s closest relatives, then we have a new and solid case of “convergent evolution” (unrelated species developing very similar traits).
This didn’t appear on my Google screen, but reader Dennis tells me that yesterday Google in Canada posted a Doodle honoring the 155th birthday of Carrie Matilda Derick (1862-1941).
Derick, a geneticist specializing in plants, was in fact the first female professor in any subject in a Canadian university. She was also the founder of the botany department at McGill University, but wasn’t made a professor for three years after she’d been running the department! (See below.) The Library and Archives Canada recounts some of her achievements, which were not only in botany, but in popularization of science and political activism:
As well as teaching and doing research, Derick published numerous articles on botany, including “The problem of the ‘burn-out’ district of southern Saskatchewan,” “The early development of the Florideae,” and “The trees of McGill University.” Many articles were aimed at the scientific community, earning her the respect of colleagues around the world and the distinction of appearing in the 1910 edition of American men of science. Others were intended to bring an understanding of nature to a general audience. In addition, she wrote biographical sketches and political essays.
At the same time that she was leading a busy and sometimes difficult academic life, Derick was deeply involved in social activism. Her main interests were women’s suffrage and education, but she worked for many causes throughout her life. Her energy and commitment are reflected in a partial list of the organizations she was involved with: the Local Council of Women (Montreal); the Protestant Committee of the Council of Education; the American Association for the Advancement of Science; the Montreal Suffrage Association; the National Council of Education; the Federation of University Women of Canada; and the Montreal Folklore Society.
Carrie Derick
Sadly, this Doodle is seen only in the blue places below, i.e., Canada. It’s the first one-country Doodle I’ve seen, and that’s a shame. It does us well to remember the indignities suffered not all that long ago by women in academia, and to mourn the loss of scientific advances caused by the marginalization of women. Wikipedia gives the evidence (my emphasis)
In 1891, Derick began her master’s program at McGill under David Penhallow and received her M.A. in botany in 1896. She attended the University of Bonn in 1901 and completed the research required for a Ph.D. but was not awarded an official doctorate since the University did not give women Ph.D. degrees. She then returned to McGill and “continued to work, teach, and administer” in the botany department. In 1905, “after seven years of lecturing, assisting Penhallow with his classes, researching and publishing, without any pay increments or offers of promotion, Derick wrote directly to Principal Peterson and was promoted to assistant professor” at one-third the salary of her male counterparts. Derick was only officially appointed as professor of comparative morphology and genetics by McGill in 1912 after three years of running the department following Penhallow’s death. She was the first woman both at McGill and in Canada to achieve university professorship. She retired in 1929.
This is my 9,970th post, which means that within the week we’ll get to post number 10,000. I’m still pondering the 172 comments on the thread following “The 10,000th post: what shall it be?“, in which readers suggested way to celebrate this landmark. If I decide to use one of those suggestions, that reader gets an autographed copy of WEIT with a cat drawn in it. Given that there will probably be nearly ten posts today, as there’s a lot to say, I expect the Big Day to be Thursday or Friday. Stay tuned.
Meanwhile, today’s Google Doodle (click on screenshot below to go there) celebrates Anna Atkins (1799-1871), a British botanist and photographer. Today would be her 216th birthday, and her distinction was to be the first person to publish any book that included photographs. In fact, she may have been the first woman to take a photograph. The Doodle gives an idea of what her photos looked like:
Anna Atkins
Here’s the title page of that pathbreaking self-published book, which appeared in 1853 (the first commercially published book with photos, by William Henry Fox Talbot, appeared 8 months later). This and all photographs are taken from the British Library’s site.
The captions were in her Atkins’s own handwriting, and the book went through three editions. According to Wikipedia, only 17 copies still exist, and they’re extremely valuable: one was auctioned off for £229,250 in 2004. But you can see the whole book for free, as the British Library has most of it scanned in (go here).
Here’s one of the pages from the table of contents, in Atkins’s handwriting:
From Vox we have some information about the process she used (their text indented):
Early photographers struggled with a problem: they couldn’t easily develop their pictures because the existing techniques were slow, expensive, or required dangerous chemicals. Herschel came up with a solution: using an iron pigment called “Prussian blue,” he laid objects or photographic negatives onto chemically-treated paper, let them be exposed to sunlight for around 15 minutes, and then washed the paper. The remaining image revealed pale blue objects on a dark blue background. This was a cyanotype — a new way to print photographs permanently.
Herschel primarily used cyanotypes to copy notes, but when Atkins heard about the opportunity, she leapt at it. Though she’d shown herself to be a capable artist, she realized instantly that cyanotypes were a better way to capture the intricacies of plant life and avoid the tedium — and error — involved with drawing. As importantly, her passion for botany allowed her to see a new application of the exciting technology.
So, in 1843, she began making a photographic book of algae.
Atkins’ British Algae was the definition of a labor of love. Published in piecemeal over a decade, from the 1840s to the 1850s, the book was made at home using her own materials. From what we know, she collected the algae with the help of her friend Anne Dixon and dried and pressed it, the same way you might press flowers. Then, she identified it using William Harvey’s Manual of British Algae. Finally, she made the cyanotype by laying each piece upon the paper (that’s why, technically, her pictures are called photograms, not photographs, because they didn’t use a camera). The book’s text appears in her own elegant cursive.
The book wasn’t a profit-making enterprise for Atkins, but it was an important one. It stands as the first book illustrated with photographs, and it brought together photography and botany for the first time. Atkins took the most fleeting and unusual of subjects — British algae — and made it timeless.
You have to really love algae to do something like this.
Psychotria elata, a neotropical plant in the family Rubiaceae, has become internet-famous because of its flowers—or rather the shape of the red bracts (modified leaves) before the flowers mature. As The Amusing Planet notes:
These gorgeous pair of red, luscious lips belong to a plant known as Psychotria elata, a tropical tree found in the rain forests of Central and South American countries like Colombia, Costa Rica, Panama and Ecuador. Affectionately, Psychotria elata is called Hooker’s Lips or the Hot Lips Plants. The plant has apparently evolved into its current shape to attract pollinators including hummingbirds and butterflies. According to Oddity Central, the bracts are only kissable for a short while, before they spread open to reveal the plant’s flowers.
Without having seen it, I am still 100% sure that Central and South American kids pick these bracts and run around with them in their mouths.
In the end, though, I think a less salacious and more appropriate name would be “Marilyn Monroe lips”
I have gone into the lab to find that my Paphiopedilum orchid has bloomed. I’m pretty sure this is not a hybrid, but a real, naturally-occurring species; sadly, I forgot the species name, but I’m sure Lou Jost or someone else will tell me, and perhaps give a bit of information about the flower:
Once a year I get this flower, which lasts for about ten days. Lovely, ain’t it?
I won’t go on about this cool new paper at length, for it’s already been described by Ed Yong at Not Exactly Rocket Science as well as in a piece at The New York Times. Still, it behooves us to know about it. The upshot is that a group of Russian scientists recovered from the Siberian permafrost a cache of seeds and fruits stashed by ancient squirrels, and managed to use tissue culture to regenerate plants from immature fruits. The estimated age of the seeds is 32,000-30,000 years old, so this is clearly the most ancient organism ever “revived.”
The plant, a species that still exists (at least the morphological similarities suggest conspecific status), is Silene stenophylla. Silene (of which there are several species) is also known as “catchfly” or “campion” (literate readers will recognize it as the flower with which Mellors the gamekeeper bedecked Lady Chatterly’s pubic hair in Lady Chatterly’s Lover). It’s often used in evolutionary studies because some species have separate sexes while others do not, and ditto for sex chromosomes. It could thus tell us something about the evolutionary origin of gender and gender-specific chromosomes. Some species are also gynodioecious (i.e. some plants are “female” [male parts sterile], while other plants are hemaphroditic), and this could also give us a clue to how “male” versus “female” plants arose.
But I digress. In a new paper published in the Proceedings of the National Academy of Sciencesby Svetlana Yashina et al., the authors describe finding a group of fossil burrows, 20-40 meters below the surface, in the permafrost of northeastern Siberia. Some of these burrows contained as many as 600,000 seeds/fruits! These were stashed by equally ancient ground squirrels of the species Urocitellus parryii:
The Arctic ground squirrel Urocitellus parryii, photographed by Ianaré Sévi.
Permafrost provides the dry and cold conditions needed to preserve seeds; that’s how they’re preserved in special seed banks. Attempts to germinate the seeds failed, but they managed to grow one species of Silene by dissecting out the “placental tissue” (special tissue in the fruit to which the seed is connected), culturing it in nutrient media and then adding hormones (auxins, etc.), to induce formation of roots and shoots. And they got the plant to grow, flower, and, after cross fertilization with other ancient plants, set seed. Here are two specimens of the plant grown from cultured ancient tissue:
The two articles cited above will give you more information. What interests me most about this is that the “species” still exists, and this allows us to see how much evolutionary change has transpired in 30,000 years. (This is similar to the way that bacterial evolutionists can freeze an ancestral culture and then, after reviving it, compare it to its descendants that have undergone many generations of evolution).
The plant appears to have actually changed during those 30,000-odd generations. (This is probably genetic rather than environmental change because the differences between ancient and modern plant are seen in the second generation of cultured ancient plants which have been produced by cross-mating them.) The authors note the differences:
Thirty-six ancient plants (12 from each fruit) and 29 extant plants were morphologically tested. All ancient plants were morphologically identical. During vegetative development, the ancient and extant plants were morphologically indistinguishable from one another. However, at the flowering stage they showed different corolla shape: petals of extant flowers were obviously wider and more dissected (Fig. 3). Moreover, all flowers of the extant plants were bisexual (b) (Fig. 3A), whereas the primary flowers (two to three in number) of each ancient plant were strictly female (f) (Fig. 3 B and C, f), and then bisexual flowers were formed on each ancient plant (Fig. 3C, b).
For those botany geeks among us, here’s Figure 3 showing the differences (click to enlarge):
The one thing I really wanted to know, and which the authors didn’t study, is whether the ancient plants are reproductively compatible with the modern ones. They crossed ancient plant with ancient plant, and showed that they cross readily, as of course do modern plants crossed with modern plants. But they didn’t cross ancient plants with modern ones! They need to do that.
If they found reproductive incompatibility in those crosses, that would suggest incipient (or full) speciation between ancestor and descendant, something that we rarely get to study because ancestor and descendants never get the chance to meet and mate (this would be like mating the 750,000 year old ancestors of Homo sapiens with modern H. sapiens, since a comparative number of generations have transpired). And even if reproductive isolation didn’t evolve, one can still study the genetic basis of differences in petal shape and appearance of different kinds of flowers. Ten to one the Russian team is doing this, and I look forward to the results.
You’d think that Darwin’s Beagle collections had been pretty well worked over, but it turns out that we didn’t even know everything that Darwin collected. According to the Associated Press, Howard Falcon-Lang, a paleobotanist at the University of London, found a cache of 314 slides of specimens collected not only by Charles Darwin, but by his colleague Joseph Hooker and by John Henslow, Darwin’s college mentor. The specimens were apparently misplaced because Hooker forgot to catalog them before he took off on a field trip to Asia. They appear to all be thin sections of fossil plants.
Imagine opening a dusty old cabinet and finding something like this:
That’s one of the specimens, and yes, that’s CD’s signature. What is it?:
This image made available by the Royal Holloway, University of London on Tuesday Jan. 17, 2012 shows a polished section of a 40-million-year-old fossil wood collected by Charles Darwin in 1834 on Chiloe Island, South America in the course of his famous “Voyage of the Beagle.” British scientists have found scores of fossils the great evolutionary theorist Charles Darwin and his peers collected but that had been lost for more than 150 years. Dr. Howard Falcon-Lang, a paleontologist at Royal Holloway, University of London, said Tuesday that he stumbled upon the glass slides containing the fossils in an old wooden cabinet that had been shoved in a “gloomy corner” of the massive, drafty British Geological Survey. (AP Photo/Royal Holloway, University of London, Kevin D’Souza Ho)
“It took me a while just to convince myself that it was Darwin’s signature on the slide,” the paleontologist said, adding he soon realized it was a “quite important and overlooked” specimen.
He described the feeling of seeing that famous signature as “a heart in your mouth situation,” saying he wondering “Goodness, what have I discovered!” . .
(I wouldn’t have used the word “Goodness!”)
Falcon-Lang added:
“To find a treasure trove of lost Darwin specimens from the Beagle voyage is just extraordinary,” Falcon-Lang added. “We can see there’s more to learn. There are a lot of very, very significant fossils in there that we didn’t know existed.”
Falcon-Lang expects great scientific papers to emerge from the discovery.
“There are some real gems in this collection that are going to contribute to ongoing science.”
Well, maybe, though my guess would be that they’d contribute more to the history of science than to ongoing research. We shall see.
