Last week I visited Vasquez Rocks, and wrote about the trip in this post. While the geological features were neat, what really interested me were the critters growing on the rocks. After all, what organismal biologist can go to a park with the word “rocks” in the name and not look for lichen?
For those who don’t remember Bio 101, lichen are a symbiotic organism: they’re a fungus and either a green alga or cyanobacterium living as a single unit. Fungi are masters of living in dry, dessicated environments with low nutrients (many plants have fungal symbionts that help the plant’s roots get nutrients out of the soil). However, fungi can’t obtain energy from sunlight. Luckily for lichen, algae and cyanobacteria are photosynthesis experts. Pair the two up and you’ve got an amazing organism: one that can survive in a desert, exposed to the full summer sun all day while living on nothing but bare rock. No soil to get nutrients out of. No possibility to send roots down to the water table. They’re awesome.
But from far away, lichen don’t look like much1 . After all, many species of lichen require years to grow a centimeter or two (growth rates of lichen are typically reported as mm/year). But look up close, and the beauty of these organisms reveals itself as a complexly structured body consisting of beautiful lines, textures, and colors.
Quick quiz: how many species of lichen are visible in that picture?
The gray one that fills the frame is the dominant individual, but there’s at least four species visible2. And the gray one is overgrowing all the other three. This is competition, lichen style. Lichen have only a limited amount of area where they can grow (the surface of some substrate), and inevitably they start to run into each other. Since they get their energy from light, whoever can overgrow the other is likely to win. You’re witnessing a fight to the death.
The number of lichen visible in that picture also demonstrates another characteristic of lichen that I love: they’re diverse. Walk into any given habitat that’s amenable to lichen, and within a few feet you’ll likely find a dozen or more different species. They’ll be different colors, textures, shapes, and sizes. See, for instance:
Most lichen are ascomycetes, meaning that their fruiting bodies are based around asci, which are often found in cup-shaped structures. Take a look at the picture above, and you’ll see a couple of little cups; these are their apothecia, and they’re filled with spores that will be released into the air to grow into new lichen.
Adding to the diversity of lichen is the range of sizes they come in. Compared to the two above, the ones below are growing as tiny individual units:
And with the right lighting, the textures of lichen come out just beautifully:
While much of the time lichen are found growing as large clumps fighting it out, sometimes you find a perfect specimen that’s all by its lonesome, just crying out to be photographed:
A photographer I know had the audacity to say that lichen were gross up close. I must disagree: they’re gorgeous. And I hope that you, kind reader, can now agree with me. How can you not love those delicious colors and textures, especially once you know how incredibly tenacious lichen are?
So, next time you go on a hike or are out in a natural area, take some time to look at the rocks, fallen wood, and soil around you. You’ll probably find some lichen.
2 There’s a brown crusty, cracked-looking individual to the left, a light-brown smooth individual in the top center, and a nearly-black individual in the upper-right.