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Getting to Know Us

Getting to Know Us!

Lichens are complicated little organisms. It’s incredibly easy to get lost in the little details of lichens, so I like to tell a story to help illustrate what they are and why they are so special.

Joe Walewski, a well known lichenologist, tells the story of Freddy the fungus to people of all ages at Wolf Ridge Environmental Learning Center in Northern Minnesota. Freddy Fungus had a spacious home to himself and all the necessary life skills except cooking. Alice Algae was a master cook and lived alone. Freddy and Alice met, took a "lichen" to each other and decided to live together, cohabitating together in symbiosis. Walewski’s story becomes more complicated as he introduces Cybil Cyanobacteria, who occasionally cohabitates with Freddy and Alice. (Waleski, 2007). This story illustrates the complexity of what a lichen is and its basic functioning.

While this story hints at what lichens are, a more thorough explanation is needed. Lichens consist of at least two partners, a fungus and a green algae. The fungi never exists outside of the lichen and the algae can occasionally be found outside the lichen. The fungus provides the habitat and protection for the algae while the algae provides the food. Some people say that lichens are simply, "a fungus that has discovered agriculture" (Waleski, 2007). 

Lichens can be found almost everywhere on Earth, ranging from tropical rain forests and deserts to Arctic plains and central Iowa. Since lichens can live nearly everywhere, it’s no surprise that it has been estimated that they cover six percent of the land on Earth (Gadd, 2010). Lichens are pioneer species. This means they are the first to come into an area that has been recently disturbed by events including lava flows, glaciers, and other natural disasters. Pioneer species help the area recover and, ultimately, create a more stable ecosystem. Lichens often use rocks as their substrate, and start to break down the rocks, creating soil in new environments. Lichens that contain cyanobacteria often fix nitrogen, increasing the amount of nitrogen in the soil and improving soil quality.  

Despite their enormous geographic area and vast number of species (between 14,000 and 20,000 species), lichens go unnoticed every day. Lichens live on the trees, buildings, rocks, and even the sidewalks here at Iowa State. Lichens are permanent residents of their substrate. Lichens have a long lifespan ranging from 30 to over 4,500 years (Waleski, 2007). This makes them easy to study over a long period of time, and helpful for the tour you’re about to embark on!

Identifying lichens is incredibly tricky, but no worries! I’ve gathered all the pertinent information you’ll need to start! Learn more about identifying lichens here!


Gladd, Geoffery Michael. "Metals, Minerals and Microbes: Geomicrobiology and Bioremediation." Microbiology 156 (2010): 609-43. Print.

Waleski, Joe. Lichen of the North Woods. Canada: Kollath+Stensaas, 2007. Print.

Lichen Terminology

Lichens can be complex and difficult to identify without the first understanding the basic terminology. This page describes and illustrates the terminology used throughout the lichen trail. 

Substrate: the surface the lichen is attached to: can be rock, bark, cement signs, trees, or basically anything.

Apothecia: small cup shaped structures that are on top of lichen that release sexually produced spores. The gray crustose lichen below is covered in orange apothecia. 

 Lichen with orange apothecia

Soredia: Small, asexual reproductive structures. Soredia are small bundles of fungi and algae. These are found in several of the lichen on the trail. 

 Lichen Soridea Diagram

Pycnida: Small, structures that contain spores not associated with the apothecia. These structures vary widely in appearance, ranging from small black dots on the edge of the thallus to dark orange pimples as in Xanthomedoza fulva, as featured on this lichen trail and highlighted in the boxes below.

  Lichen classification by appearance

Lichen comes in all shapes, sizes, and colors. The most broad way lichenologist classify lichen is by growth patterns :crustose, foliose and fruticose. These growth forms have no relation to family, genus, species, or other scientific classification, it is simply apperance. 

Crustose is "crusted" on lichen. Some says it looks like the lichen was spray painted on to the substrate. The lower surface almost disappears into the substrate, making it impossible to remove the lichen from the substrate without destroying the lichen.  These are the most difficult of the three growth forms to identity, but provide extreme satisfaction once the crustose lichen is identified. 

Crustose lichen

Foliose lichen tend to look like leafy growths attached to the substrate with one or more stem like structures called rhizines. These can be removed from the substrate without damaging or destroying the lichen. This growth form is the most represented lichen on the lichen trail. 

Foliose lichen

Fruticose lichen is most ornate of the three growth types. These lichens can look like tiny trees, bushes, or even tiny pixie cups! While these are beautiful and unique, these growth forms are not commonly found on campus. 

Fructose Lichen

Feeling ready to go? I hope so, because you can click on Stop 1 whenever you're ready!


Image Sources:



All other: Emma Runquist