The Remarkable Lichen

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If you spend any time outdoors, you have likely noticed some odd residents growing on rocks, sidewalks and tree trunks. With shades of gray, green and blue, growing interspersed with mosses, these organisms are often mistaken for plants. Closer inspection reveals that these residents – lichens – are something unique among living things.

So, what exactly are these growths that continue to puzzle even modern day scientists?
As many of us learned in high school biology, a lichen is an example of mutualistic symbiosis, where two organisms grow together and both benefit. In this case, a fungus forms a protective shelter that houses a photosynthetic organism, usually a type of algae. The algal cells produce nutrients, which the fungus feeds from and grows. Seems simple enough, right? Just wait.

As lichenologists began looking closer in the lab, they realized there was much more going on here. When separating the fungus and the algae, they couldn’t recreate the same structure seen in the lichen. When the two were together, they transformed into something completely different from either component. The lichen appears to take on a life of its own and shows characteristics not seen in either the fungus or algae.

As for that beneficial relationship, new research suggests it may not be as friendly as previously thought. The fungus actually breaks down the algal cells, causing them to leak nutrients. Since leaking cells are rarely seen as a sign of health for living things, some lichenologists think this relationship may be much more beneficial to the fungus. Luckily, the algae can reproduce much more quickly than the cells are destroyed, so the lichen can continue to grow.

Lichen and algae on a branch (Photo by Rob Mitchell on Flickr)

Could lichen inspire the next fashion trend?
With its wide range of color and texture, there is no question that the world of lichens is beautiful. However, to see a runway show of clothing made from lichens, we likely need to head outdoors and take a closer look at the trunks of trees. If you are lucky, bits of lichen may start to move around. Look a little closer and you will notice it seems to have sprouted legs. This little lichen bug has covered its back in lichen in hopes that it will not be noticed by its predators or prey.

In the realm of home décor, some birds use lichen to line the outside of their nests. The most well-known example is hummingbirds. By using the types of lichen growing near the nest site, they are able to camouflage the tiny home and protect their young from predators.

A blue gray gnatcatcher’s nest camouflaged with lichen (Photo by USGS Bee Inventory and Monitoring Lab on Flickr)

How can I learn more about lichens?
If you want to learn more about lichens, the Ohio Moss and Lichen Association is a good place to start. Start by reading up on the growth forms and then get out and explore. During the day, a hand lens may be helpful for making observations. At night, you may opt for a black light, as some lichens will fluoresce with vibrant colors. As always, feel free to stop in and chat with one of your Great Parks’ interpreters with any questions you may have.

Lichen on concrete (Photo by Stephanie Morris)

Stephanie Morris, Nature Interpreter