Feb 6 2020
What is a Lichen? Lichens are a fungal lifestyle: fungal species that grow together with algae or other photosynthesizing lifeforms to form a whole new, symbiotic organism. Symbiosis is when two (or more) different organisms grow closely together. These relationships can be negative (like parasitism) or positive, when all organisms benefit. Lichens are an extreme form of symbiosis where the organisms live physically intertwined. The different parts of this symbiosis are called symbionts.
Lichens are formed by a mycobiont (fungi) combined with a photobiont (green algae, or occasionally cyanobacteria). The algae (or bacteria) use photosynthesis to create sugars, which the fungal symbiont uses as food. The majority of lichen fungi do not live as free-living organisms, but rely on this relationship to exist.
When you see perfectly round circles on lichens, they are the fruiting bodies of the fungus, or apothecia, which create fungal spores. The spores will be released into the wind, to settle down and germinate, and hopefully find the algae it needs to create a new lichen.
An easier strategy is to reproduce by breaking off little bundles of pre-made lichen - a few algal cells surrounded by fungal cells. These can break off of the lichen, and if they make their way to suitable substrate, they can grow into a new individual.
Lichens grow everywhere - from coastal rocks to old-growth forests, from deserts to the tops of mountains, tropical rainforests to Antarctica, even in the middle of cities. Look for lichens in your life!