Collection location: Turnbull National Wildlife Refuge, Spokane Co., Washington, USA [Click for map]
47.4125° -117.5757° 706m
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|I’d Call It That||3.0||0.00||0|
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|I’d Call It That||3.0||10.23||2||(Nastassja Noell,jason)|
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Just so long as everyone is aware that I make up half (at least) of what I say as I go along… :)
stimulated by a “lowly” lichen.
This is critical to understanding the crazy forms of lichens — all those absurd eye-lashes and plates and bushy rhizines and protuberances and black stains. This is at the core of Trevor’s new way of looking at lichens.
Gauslaa finally explained the mechanism, but I only sorta grasp the inner workings. Photosynthesis has to be kept “clean”. If it fixes too much carbon, it builds up in the chloroplasts and gums up the works and it can cause permanent damage. (Too much light can also damage the machinery.) So if the alga is photosynthesizing, and it’s producing all these sugars, something has to use them. But they’re just C, H and O. You need N to produce amino acids and proteins. (And you need P and other nutrients for fancier stuff, I guess, I get lost in chemistry really quickly.)
Enter the lichen secondary substances. Atranorin, anthraquinones, usnic, norstictic, gyrophoric acids, etc. All of the literally hundreds of different compounds that all lichens seem to produce at some point or other. They are all just C, H and O. They are one of the easiest ways to get rid of extra carbon in an energy-rich environment. (And some additionally provide sunscreen, protection from herbivores, pigments of various types, energy storage maybe, and probably other things no one’s every thought of.)
And there are other ways of dumping excess carbon in a hurry. Excrete it as black pigments. Build cilia and bushy rhizines and thickenings. Next time you see a delicate squarrose rhizine on a Physconia under the dissecting scope, try to picture it in your mind as carbon literally crystallizing out of the air. That’s what lichens are doing. They’re crystallizing these elaborate structures out of thin air.
So fascinating that U. torrefacta grows by the plates pushing out of the margins. I would have never ever guessed. I see now why there are pin prick holes – they are seams. Beautiful. Like a quilt. And then with my well developed sample, its like Grandmas quilt got so big that grandma and her rocker got pushed up into the corner, and she had to stop adding new pieces cause she ain’t go no room to maneuver and do so.
Pinprocks – other adaptive benefits… even if it is an accidental side effect, it must have adaptive benefits too, that pattern is always present, right? The multi-functionality principle it should be called. I wonder if the pin-pricks assist in helping the lobes to be sewn together, so that air pockets can be formed beneath it, thereby helping the U. torrefacta to heat the air that rests between it and the rock it is resting on. It is amazing that it gets up to 80*C. Have you seen those ecology charts about optimal metabolic function in relation to temperature, like how the Arctic fox can maintain optimal metabolism even a temperatures far below 0*C. Wonder the different ranges of Umbilicarias. But maybe we need not even go that far, instead just look at the range in habitat and different growth forms. And if there are more pin pricks in U. torrefact that are found in the desert, vs. ones found in more cloudy areas like Turnbull, then perhaps it assists in heat release, or less heat absorption, so that enzymatic processes are not halted by too high of temperatures. (I just love thinking about the tertiary structure of proteins, and how they change in relation to temperature. Like dancing, gotta get warmed up and get your flow on with your surrounding partners, but can’t start moshing at the ball :)
The central rhizine you say could be good for getting rid of excess carbon. Now that is fascinating, because I don’t even grasp what you mean. Why would a lichen want to get of excess carbon? Why would there be excess carbon? And how would it do so through the rhizine? By thickening the rhizine? Adding the excess carbon to thicken its rhizine rope? That is a whole new box in my head now – “excess carbon” is scribbled on the outside. Fascinating.
Yours are very well-developed specimens. Look at how the thallus of Umbilicaria species grows. Most species grow at the center, not the margin like most other foliose lichens. This results in the umbilicate form with tattered margins. That’s the typical mode, but there are variations. U. torrefacta is one of those variations. It’s formed of all these tiny plates, instead. The plates seem to be created at the center and get pushed out, but the margins of the plates seem to continue to grow. Given time and the right conditions, the plates will fuse so completely that no light is visible between them. You can see it both above and below. At first, a “fast-growing” (ha!) specimen will look like the one on Umbilicaria page you referred to, with really rhizine-like plates below and big obvious chinks all over the upper surface. But look at yours, especially the one on the bottom left of the top photo, it looks like an intricate jigsaw puzzle, right? The plates in yours have completely fused, are even becoming a bit convex and hyperborea-like because they’ve run out of room to grow. Maybe it’s because they are so big and the growth at the center is no longer capable of forcing the outer parts of the thallus to expand, who knows? But the ontogeny is clear if you know how to read it, I think. No question this is torrefacta.
Question is, are the pinpricks just an accidental side-effect of the platy growth mode? Or do they provide some adaptive benefit themselves? The species tends to grow in particularly arid locations (acc. to Trevor), and this seems plausible in my limited experience. Why would pinpricks help? Extra ventilation? Greater photosynthetic surface for the given volume? These things stump me in the best of circumstances. Gauslaa told me their story in the field one day: the dark brown color makes them much hotter than other lichens, like up to 80°C(!) (He has thousands of numerical figures like that at the snap of a finger, what a guy! :) So, if I remember it correctly, these things often grow in snowy exposed places where wind will uncover them in the winter. The color then elevates the temperature enough for them to grow using the meltwater of surrounding snow. In the winter. Gauslaa is Norwegian, and this seems very plausible for the alpine/arctic/boreal species, I’m not sure what the story is for desert species like phaea (and torrefacta?) But if we take what he’s saying at face value, it tells us what the conditions are when these things are growing: cold, with a steady supply of trickling snowmelt. Note, also, as Trevor has pointed out to me, that they grow almost exclusively on vertical or at least slanted rock surfaces. That means water from snow melting above them, say on the top of the boulder or cliff, will run down the rock under these species. Why the umbilicus? Maybe competition. It also gives them a place to get rid of excess carbon (rhizines and plates and verrucae on the lower surface). The rhizines and such could well help wick moisture. All of this is plausible enough, maybe, but why perforations? I’ve still got no clue! Any ideas?
Useful for identification, yes, definately :) But what about for the lichen? To let light through to the lobes underneath? To be pretty in a lace dress? :)
Your photo of the perforations is awesome. I’m wondering though if mine is that starry, not really, a bit, more like an LA sky, and the rhizines aren’t as dense, argh, calibrations needed indeed! But the underside is definately platy – not seeming to be papillose like in U. phaea … tricky :)
Next time you see an U. hyperborea with perforations, compare it to any U. torrefacta. Yes, it has some holes, but it’s nothing like torrefacta. It’s like the stars in the sky over Los Angeles compared to over the Sierra Nevada. No comparison! :) I’m just warning you that it’s a bit ambiguous the first time you see it — it needs to be “calibrated”, as it were.
I wonder why the perforations are useful…
It can be much more obvious than this. You’ve probably noticed that U. hyperborea can have some perforations, too. But I think you’ve got it. I just looked over all my photos, and the critical conserved features seem to be: U. hyperborea is smooth below, and it has distinctly convex “worms” on the upper surface. U. torrefacta has chinks and holes and “messy” texture on the upper surface, but never packed lumpy “worms” if you get my meaning. Also the lower surface, even when it has no or few obvious plates or rhizines, is always at least rough. But even the apparently plateless ones, if you look closely, you can see where the plates have just fused together into a continuous surface. I can’t see this last bit on your photos, but everything else is right on.
Created: 2012-09-06 00:36:38 CDT (-0400)
Last modified: 2012-09-06 13:15:54 CDT (-0400)
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