Some Farmers Are Fun Guys; Others Are Fungi

Trevor Goward, a Canadian lichenologist, describes lichens as “fungi that have discovered agriculture.” Lichens consist of two (occasionally three) species: a fungus and an algae or a cyanobacterium. Cyanobacteria are also known as blue-green algae, but they are in a different kingdom of living organisms (e.g. animals, plants, etc.) than the true algae, and are closely related to bacteria.

Each species has roles to play in the lichen. The roles are numerous and complex, but generally the algae or cyanobacteria produces food using photosynthesis to make sugars out of carbon dioxide and water using energy from sunlight, and the fungus provides water retention capacity and protection from the elements. Such a relationship between two organisms is called a symbiosis. Although the lichen symbiosis is often used as a classic example of a mutually beneficial symbiosis, a good case can be made that the relationship is better described as a fungus that is parasitic on an algae or cyanobacterium.

Lichens are broadly categorized into three growth forms: foliose, fruticose, and crustose. Today's tidbit features a few species of map lichen (Rhizocarpon spp.), which are crustose lichens. Crustose lichens grow tightly fused to the substrate, typically a rock or the bark of a tree. The photograph was taken by WPC's Botanist, Steve Grund.

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