On a walk through the woods, most of us would probably be able to point out a couple varieties of lichens. We find them on broken branches that have fallen from the forest canopy. Others grow on shorter trees void of direct sunlight. Lichens even exist rooted to rocks. But what do we really know about these organisms?
I was surprised to find out that lichens are actually comprised of a fungus and algae, coexisting together to create a single entity. The fungus provides the structural stability, water and minerals, while the algae is in charge of the photosynthesis.
For the most part, the relationship of the two life forms is considered to be mutualistic, but some scientist characterize the association as partially parasitic since the fungus penetrates and absorbs half of its partner’s nutrients.
There are approximately 20,000 species of fungi that exist only in partnership with algae to form lichens (this is around 20% of the known fungal species). And of these, none are found without their partner in the natural environment.
Many lichens are exceptionally hardy, and can exist in extremely adverse environmental habitats. They can survive in arid deserts, severe cold locations, as well as high elevations. They can also remain dormant for long periods of time, waiting for favorable conditions. However lichens tend be remarkably sensitive to pollution, and generally do not grow well in tainted areas.