See, if you tilt the camera, the rocks slide downhill. Wait. . . let me check my notes . . . A photograph of the fascinating Racetrack Playa in Death Valley, California, USA. Creative Commons djfrantic. Click for link.

It turns out there’s a perfectly cromulent explanation for this effect; if you don’t know it and want to spoil the magic, see here.

Well, it turns out that this organism,

Sooooooo cute. I'm waiting for the plush version from Etsy. Grimmia trichophylla. Creative Commons johndal.

or one of its close relatives, I should say, can apparently do the same, or something like it. Don’t believe me? There were three photographs and a fascinating account of the phenomenon over at Botany Photo of the Day last week — the most important bits are paragraphs two and three. Don’t miss it! Once you’ve read it, come back here for a little commentary . . .

OK, finished?

Now, my friends, you can see why geologists hate “vegetation”. For in addition to your garden-variety and annoyingly rock-obscuring trees, shrubs, flower, and soils, they must also contend with the biofilm of lichens — little fungus-alga co-ops — and naked algae that encase every rock in sight after a few decades. That means that nearly every rock face you look at is not its true color; it’s the color of the encrusting life. The day the light bulb blinked on and I thought, “That cliff isn’t gray-green. The rock is pink and the stuff living on it is gray,” was one of revelation for me.

This further explains why geologists flock to newly blasted road cuts like flies to honey, and further why they carry around rock hammers* for splitting rocks to see what they truly look like. It also explains why I get nervous around them when they get that glimmer in their eyes suggesting that if they could napalm the countryside in their research area, they would.

When I reach the summit of mountains in Colorado, I’m astounded by the variety of lichens, moss, and algae I find there. Mountaintops are lichen biodiversity hot spots, splashed with green, yellow, black, gray, and orange.

A fiesta of lichens (can I coin that term for a lichen herd?) at Rocky Mountain National Park. Creative Commons shrocket.

Thrillingly orange lichens are particularly common up there, since they thrive in places birds poop (and thus fertilize), and birds seem to like perching on rocks near the summits of mountains where they, like us, have a clear view of the countryside. And yet, almost no one looks down or looks carefully, and with enough foot traffic, the encrusting life dies and peels off.

Apparently, mosses can also induce lichen holocausts as they slide down rock faces. How they do this, I know not, although the lack of light may play a role. But notice there aren’t simply dead lichens in their wake; the rock is scrubbed clean. Which leads to another interesting hypothesis: the moss excretes acids or some other chemicals that allow them to digest the biofilm on the rock surface and absorb the resulting nutrients. Would that make these mosses . . . herbivores?

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*Also because physical and chemical processes called “weathering” alter the surfaces of rocks. Also, by coincidence, they note that in the first two photos of the galloping moss, they are galloping upon the fossils of 1.9 billion year old cyanobacterial mats — thin films of blue-green bacteria that slowly build up characteristic striated rocks called stromatolites. In ancient times, these were prolific and their fossils are common, but today, stromatolites, crowded out by us pesky multicellular organisms, are found in only a few places on Earth, most prominently in the Hamelin Pool in western Australia’s Shark Bay. Interesting biological coincidence!

Living on the moist, warm ground were moss and liverwort gardens 30 feet across. Wait. . . liverwort? Liverworts are amazing moss relatives that can produce leathery lichen-like bodies with an emporium of odd-looking reproductive structures. They’re called liverworts because supposedly, their odd protuberances can resemble livers. In medieval times, people thought that if a plant looked like something, that was God’s way of telling you that it was good for treating it, a philosophy called the “Doctrine of the Signatures”. So if your liver was ailing you, you might get a tincture or powder of liverwort to take. As it turns out, that’s not such a great way to identify potential drug candidates, but I digress. . .

The geeky-cool liverwort, likely Marchantia of Botany 101 fame. http://www.flickr.com/photos/benetd/ / CC BY 2.0

The most well known liverwort — Marchantia — makes fake-palm-tree-like female reproductive stalks and nail-like male ones (not pictured). It’s such a successful little guy that this species has even become weedy. When I worked at a garden center one summer after graduating college (yes, the first job I got with my shiny new bachelor’s degree was weeding and watering plants) it was not uncommon to find liverworts crowding the soil at the base of a plastic pot. Apparently the twice daily (at least) watering routine at plant nurseries agrees with them.

In the wild, these little plants are often found growing near brooks, even here in Colorado, where I have seen them (uncommonly) growing next to streams in Rocky Mountain National Park. In the above picture, you can see another of their crazy reproductive structures, asexual gemma cups. They look like little bird nests. In the cups, little lens-shaped or spherical tissue packets called gemmae are formed asexually. When raindrops land in them the gemmae are splashed out and land on soil elsewhere. If they start growing and take root . . . voila! New liverwort.

The leafy liverwort Jamesoniella autumnalis. Used with permission courtesy of Robert W. Freckmann Herbarium, University of Wisconsin, Stevens Point.

However, that’s a thalloid liverwort. The leathery projections in the photo above are referred to as a thallus or thalli (pl.), because they are undifferentiated (into leaves, stems, etc.) plant tissue. But there is a second type of liverwort: leafy. That’s probably a bit deceptive because mosses and liverworts (a group referred to as bryophytes) don’t have true leaves, shoots, or stems, a botanical nicety whose explanation I will spare you for now. The liverworts found atop Socompa appear to be of this type. When scientists sequenced part of their DNA, they found they were most closely related to a species called Jamesoniella autumnalis, which can be found in North America. Here is a picture of one found growing in Wisconsin.

And here are its crazy reproductive structures:

Can you get PBS with those? The sporophytes (spore making plant) of Jamesoniella autumnalis. Used with permission courtesy of Robert W. Freckmann Herbarium, University of Wisconsin, Stevens Point.

To keep this post from turning book-length, I’ll merely mention that, believe it or not, the pointy-looking things you are looking at in this photo are a completely different organism of the same species as the plant they are growing out of. Plants do an amazing thing called “alternation of generations” in which they alternate between haploid (one copy of genes) and diploid (two copies of genes) organisms. All plants do this — even petunias and apple trees. Where is the second plant of those species? Ahh . . . I’m glad you asked. But that shall have to remain a mystery for another day. : ) In this case, the green thing underneath has single chromosome copies, and the pointy things above have the dual, and their sole purpose, as they parasitically grow out of their parent plant, is to grow tall enough to broadcast the spores they are making inside those little black heads.

The mosses that were found on Socompa were related to the copper moss (love that name!) Mielichhoferia elongata which, as far as I an tell, look pretty much like your standard moss but tend to grow on copper-rich rocks. That’s not surprising, given that a few miles west of Socompa is — the Escondida Copper Mine. Mosses also have alternation of generations and a beautiful but somewhat less eclectic selection of reproductive structures, but I will save that discussion for another day.

It’s unsurprising to find mosses and liverworts at such a spot on Socompa because mosses and liverworts are what biologists would call “ancestral” — that is, they more closely resemble the common ancestors of plants than conifers or flowering plants do. They are of a form that is necessarily tied to water, since those ancestral plants had only recently left the oceans. In fact, mosses and liverworts cannot live without flowing water during at least part of their lives, because to make that pointy thing (called a sporophyte — or spore plant), a sperm has to swim out of the boy-part of the plant through a film of water on the surface of the plant to find the girl part of the plant. How’s that for sperm mountaineering? But aside from their need for water, bryophytes are quite hardy. When the first plants sprouted out of the seas, land was probably a forbidding, empty, UV-drenched place. Sound familiar?

I’m going out of town today, but next week I’ll be back with a look at some other great critters from Socompa.

For instance, a press release on one of the coolest things I’ve seen in a long time includes this sentence, seemingly lifted from Timmy’s 3rd grade report on mosses:

At first glance, mosses and human beings have little in common.

Gee, ya think? I’m imagining myself at a coffee shop holding a cup of steaming tea and sitting across the table from a noticeably uncomfortable bryophyte.

Cough. *Blink*

Me: So, read anything interesting lately?

Moss: No.

See? Not much in common. Strangely, this doesn’t differ greatly from most of my actual dates.

I don’t want to seem too hard on the author here, since 1. the release was probably first written in German, and 2. this is actually one of the clearer and more helpful press releases I’ve read. In any case . . .

Scientists from ETH Zurich and the University of Freiburg im Breisgau report that they were able to insert DNA from humans and bacteria into the moss Physcomitrella patens (sounds suspiciously close to “patent”) and the moss was able to manufacture human proteins without any further help. Yes, they basically cut and paste. And the moss said: OK! Cool!

The protonema of Physcomitrella patens. When the spore of this moss lands on a suitable spot, it starts growing into filaments like these. Given enough time, these little filaments will grow into a full-grown moss plant. You can see the chloroplasts, or light harvesting equipment, as little green circles.

For those of you unfamiliar with the Way of the Cell, DNA makes RNA (with the help of proteins called RNA polymerases), and RNA makes proteins (with the help of cell organelles called ribosomes). The reason this moss-cular feat is astounding is that doing the same thing with flowering plants will get you nada. The mammalian gene start and end sequences have evolved themselves right out of business when placed in a similarly much-modified flowering plant. Not that there’s much of a reason that that would *ever* happen in nature. Now in an evil mad plant scientist laboratory, on the other hand . . . Belgians + petunias = Brussels sprouts. Mwa ha ha ha ha ha . . . . .

How is it mosses can do what so-called “higher” plants cannot? It’s a mistake to think of mosses as “primitive” in the sense of “inferior”. Both mosses and flowering plants have ancestors that were alive at the same time. What mosses are is “less-derived”, in biologist-speak. The lineage that gave us mosses just didn’t change as much over time as the lineage that produced flowering plants, because they found they were well-adapted as-is to their particular niche (forests, rocks, sidewalk cracks, and the sets of “Lord of the Rings” adaptations). Like sharks, they found a sweet gig and they stuck with it.

According to Ralf Reski, botanist and co-author of the paper announcing this discovery, as part of this cozying into a niche relatively early on for multicellular life (moss seem to have sprouted out of the ocean and then pretty much called it a day) mosses have stayed genetic generalists. And this easy-going gene-set enables them to translate a wide range of DNA. In fact, hold on to your hats . . .

This cross-kingdom conservation of mammalian and moss protein production machineries is phylogenetically profound, and has several implications for basic and applied research. Comparative genomics, as well as functional studies, have recently established major differences in metabolic pathways and gene function between flowering plants and P. patens, and have suggested that a substantial moss gene pool is more closely related to mammals than to flowering plants (Frank et al., 2007; Rensing et al., 2008).

—Plant Biotechnology Journal, Volume 7, Issue 1, 2009. Pages: 73–86

Dude! An article in the Plant Biotechnology Journal just blew my mind!

Who knew? Well, maybe John Wyndham.

In my next post, we’ll take a look at what on Earth possessed these scientists to stuff human genes into a soft, green, cushiony object and at why biology is WAY cooler than nuclear physics. Stay tuned.