I'm Lichen This Blog

This week Nature Minute will take a look at another unsung hero of ecology, the oft-overlooked lichen. There are many different lichens and they can be found just about everywhere. You’ve probably seen lichens. Maybe a greenish-gray circular spot on a rock, or on the bark of a tree (mistakenly referred to as moss).

Last year, I did a two-part series on the importance of soil. Lichen is just as important to life, if not more so, because lichen will frequently colonize bare rock and secrete chemicals that break down the rock. Thus begins the making a toehold for more advanced plant life to follow. This succession is the beginning of soil formation.

Notice above I said “many different lichens” and not “many species of lichens”. That was intentional, because while a lichen is a living organism, it is not a single species, but a symbiotic odd couple relationship between a fungus and an alga (singular of algae). Some lichens will have a green alga, some will have a blue-green alga, and still others will have both.

How does this crazy living arrangement work? The fungus provides the lichen’s structure. The algae provides the food through photosynthesis. In many cases, the fungus and the alga are perfectly capable of living on their own. Yet for some reason, sometimes they chose to live as roommates in a lichen apartment. There must be an evolutionary advantage.

Perhaps it is the chemicals produced by lichens. Very few insects munch on them, although tundra animals will. They are also very hardy, able to withstand complete desiccation. I don’t know of any fungi or algae that can do that on their own.

Because of the separate living components of lichen, it is impossible to trace the evolution of lichens like we can trace other organisms through DNA and the fossil record. So scientists can’t say how this unlikely partnership formed, although they can tell us how new lichens are made. Because it’s different species living together, you can’t just have a male lichen mate with a female lichen. The fungus and alga can reproduce individually, but their offspring won’t necessarily form a new lichen. However, the lichen can form a soredia, a group of the alga’s wrapped up in filaments provided by the fungus. This little ball of oddities rolls off and starts a new lichen. Another way for lichens to “reproduce” is for a piece of lichen to flake off and drift to a new home.

I hope you enjoyed this week’s fascinating look at one of nature’s weirdest partnerships. Now that you know how weird those mundane little blotches are, maybe you’ll take a closer look. Enjoy some lichen photos I’ve taken during my sojourns. Lichen information this week comes from the USForest Service and the University of California’s Museum of Paleontology here and here.

Lichen on a rock in Idaho

Lichen on a rock at Yellowstone NP

Several small patches of lichen on a rock

Lung lobaria lichen on a tree in Washington

Lichen in the branches of a tree in Washington

Lipstick cladonia on a tree stump

False pixie cup on a tree stump