Now that I’ve convinced you you probably shouldn’t take your next vacation in the Atacama Desert (unless you’re into that sort of thing, if you know what I mean), let’s look at the organisms that scientists did find living and loving life in the 3 3/4 Mile-High Club.
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 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.
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:
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.