Lichen can’t be discussed without talking about cohabitation — two partners living in one space. In this case, it’s on the surface of rocks and trees, and the two partners are fungi and microscopic algae. Fungus, a non-photosynthetic organism, provides a refuge for the algae while also absorbing moisture from the air and minerals from the surface it sits on. Alga contains chlorophyll, which through photosynthesis provides food (a mass of green cells) for both members. In other words, fungi provide the shelter, algae provide the food. Thus, lichen is the symbiotic union of fungus and alga.
Living together must suit this organism because lichen can live endlessly and in extreme temperatures, as long as it occasionally has moisture. If there’s no moisture, it will simply lie dormant, awakening when above-freezing temperatures make photosynthesis possible for the algae to produce food. Lichen reproduces by wind-dispersing spores, and by storms spreading broken pieces of lichen, which attach to new surfaces.
In the Sierra, we are treated to a variety of lichen. Brown-eyed wolf lichen (Letharia columbiana) is prevalent on the trunks of firs. Its “brown eyes” (apothecia) are the fruiting bodies where spores are made for reproduction. The “wolf” name stems from its historical use as a poison for wolves. The more simply named wolf lichen (Letharia vulpina), aka staghorn lichen, is often seen adjacent to its brown-eyed sister. According to the “Sierra Nevada Natural History” guide, wolf lichens are indicators of winter snowpack levels since they don’t grow under snow. Both of these lichens have spiky, florescent yellow-green, coral-like branches (fruticose lichen), while other lichens form brown, black, gray, or bright yellow, green, and orange circles of velvet (crustose lichen). Still others have leaf-like lobes (foliose lichen).
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