What are the orange "paint" splotches decorating Isle Royale's bedrock shoreline? The scraggly pale-green moss-like beards hanging from trees? And what about the many-branched coral-like clumps on the ground? Why, they are all lichens, of course... specifically elegant lichen, old man's beard, and reindeer lichen, respectively. Island lichens and mosses are often neighbors growing in many of the same habitats and sometimes may be confused. Lichens generally differ from their mossy neighbors in three ways: lichens lack a bright green color, do not have leaves, and have a more leathery texture.
Lichens are formed by the "marriage" of a fungus and often a green alga. The fungal partner absorbs water, protects the alga/bacterium from too much light, and provides structure and anchorage for the lichen. The alga, in turn, photosynthesizes food for its fungal partner, which is not capable of making its own.
There are three basic types of lichens. Crustose lichens are crustlike and "cemented" to their substrate. Foliose liches are leaflike and loosely affixed to their substrate. Fruticose lichens are either upright and shrubby, or form long strands.
Lichens were probably some of the first organisms to colonize Isle Royale because of their unique ability to grow on bare rock. The lichens here may be hundreds of years old, and some species grow as little as one millimeter per year! Thus, special care should be taken to avoid damaging them when walking over terrain where they are growing.
Did You Know?
Although the yearly number of visitors to Isle Royale is less than Yellowstone receives in a day, the Island's per acre backcountry use is the highest of all National Parks in the United States.