“Allie Algae and Freddy Fungus took a lichen to each other,” is a verbal device used to teach children the two component parts of lichen. Minus the human names, this is a pretty accurate statement. Lichen is a result of a symbiotic relationship between a fungus and algae. It is not technically a species, but rather a partnership. Some go as far as to call lichen “small ecosystems.” They come in a stunning variety of colors and shapes, and are able to survive in even the most inhospitable places.
The fungal portion of lichen creates a structure of fungal filaments for the two organisms to coexist, and are usually from the phyla Ascomycota. Algae are autotrophs, and supply food to the partnership through photosynthesis, the process by which sunlight is turned to fuel. The three types of algae commonly found in lichen are green algae, orange algae, and blue-green algae called cyanobacteria. The latter is not always considered algae, but it serves the same photosynthetic function as other algae to feed the lichen. Lichen reproduces either in a self-propelled manner, or using the assistance of other organisms. On their own, they can shoot out algae and fungus to make new colonies where they land, or they can form scrumptious looking nodules which animals will ingest and then carry to other places.
The body of a lichen organism is called the thallus and can come in four different forms: foliose (flat and leafy), crustose (forming a crust on hard surfaces), fruticose (resembling a small plant), and squamulose (made of scales that lie flat on a hard surface). Colonies created through explosive reproduction can often create giant growths on the sides of stones, trees, walls, and other surfaces. The growths can sometimes look like giant crusts, but sometimes they can form far more interesting shapes. Some lichen can become stringy and ethereal, such as Beard Lichen which hangs delicately from tree branches. Others are almost floral in appearance, like the Pixie Cup and Matchstick Lichens.
Lichens are often edible; the Laplanders of northern Finland depend on Lichen as a food source, and hunter-gatherers in Libya often eat crustose lichen found on rocks. Lichen is also used to create dyes because of the colorful algae that are housed in them. Lichen is also very sensitive to pollution and is used by scientists to monitor pollution levels through tissue dissection and toxin measurement.
Because of their ability to feed themselves using light alone, lichen are able to establish colonies in extreme climates. They live in tundra, highlands, arctic climates, rocky coastlines, and deserts. Lichen has even been proven to survive in outer space, giving support to the idea that life is possible outside of Earth’s atmosphere.
For their hardiness, their aesthetic beauty, and for their practical uses, lichen continues and will continue to fascinate people of all ages.