Naturalist Notes

Lichens

by Jennifer Kidder

What organism ranges from Earth’s poles to the equator, intertidal zone up to the highest mountain peaks, and lives on soil, rock, bark, and even the backs of some insects?

Answer: Lichens! World wide there are an estimated 14,000 species. Here in North America scientists estimate their are 3,600 different species of lichens.

Lichens, though considered one species, are actually a combination of two different types of species. The relationship always includes a member of the fungus kingdom and either a green algae or a cyanobacteria.

Why would organisms from two different kingdoms live so closely together?

A fungus and its photosynthetic symbiont establish a relationship that generally benefits both of the organisms, though perhaps the fungus more than the green algae or cyanobacteria. The fungus provides the structure (housing) for the pair while the green algae or cyanobacteria provide the food. Fungi that enter into symbiosis with lichens are unable to live on their own, though the green algae or cyanobacteria would be able to survive apart if they were not trapped inside the fungi.

Cladonia sp.
photo by Joe Walewski

Yes, some lichens are eaten, and many are used in science to benefit humans. One common and exciting use of lichens is environmental monitoring. Because lichens grow slowly and absorb their nutrients from the substrate, air, and water they come in contact with many minerals. If lichens concentrate too many toxic elements like sulfates and other metal compounds, it will kill the photobiont and result in the lichen’s death. Using lichens to monitor acid rain and air pollution is a relatively new and inexpensive way to monitor air pollution (biomonitoring).

Lichens are identified taxonomically as if they were fungi. About 15,000 fungi can be found in relationships with lichens while less than 100 green algae or cyanobacteria join fungi in symbiosis. While some lichens can be identified by appearance, the best way to identify lichens is first by their form and secondly by chemical tests. Many lichen identification tests involve the use of highly toxic chemical reactions.

What are the basic lichen forms?

Three lichen forms are commonly used in the identification of species: foliose, fruiticose, and crustose. They describe the appearance of lichens.

What lichens are common to Minnesota?

In Northeastern Minnesota we have about 700 species of lichens. The six below are commonly found.

Individual lichens have been known to live for over 2,000 years.

In Minnesota moose, white-tailed deer, flying squirrels, and spruce grouse have been known to eat lichens.

Ruby-throated hummingbirds utilize lichens in their nest building.

Click on http://www.lichen.com for the website about lichens put together by Sharnoff, Sharnoff, and Brodo, authors of the ultimate lichen book: Lichens of North America.

See Wolf Ridge naturalist Joe Walewski's lichen page.

References

Brodo, Sharnoff, and Sharnoff. Lichens of North America. New Havea: Yale University Press. 2001.

Media. Michigan Lichens. Bloomsfield Hills: Cranbook Institute of Science. 1996.

Walewski. Wolf Ridge Foliose and Fruiticose Corticolous Lichens. Finland. 2003.