Natural History Story

The natural history story I will be describing is about the Common Greenshield Lichen (Flavoparmelia caperata) which I observed on the bark of a coast live oak tree up in the hills above campus.
This is a very common type of lichen, which as we discussed in class is an amazing thing because, although it sorta looks just like a normal plant, it is in fact a mutalisitic relationship between two very different organisms, a fungus and either an alga or a photosynthetic bacterium.

The lichen's body is actually made up of fungal strands, but under the upper surface there is a layer of either one-celled green algae or bacteria. Most lichens, including the common green shield lichen, have green algae. The algal cells are able to photosynthesize, using the energy of the sun to provide sugars for themselves and for the fungus. As one scientist described the situation, "Lichens are fungi that have discovered agriculture."

Lichen fungi are never found growing alone, without their algae. They are thus dependent on the algae for survival and cannot get food in any other way. The algae on the other hand are perfectly capable of living on their own. This leads some scientists to describe the relationship between the fungus and the algae as a parasitic one, where the fungus is exploiting the algae but not giving another back, or at least as an asymmetrical mutualism.

However other scientists disagree, saying that inside the lichen the algae are more protected, and so do get some benefit from the relationship. Lichens can often grow in habitats much drier or more exposed than the algae can survive in alone, another benefit for the algae by expanding the possible niches in which it can grow.

This lichen also has a mutualistic relationship with the oaks that it lives on, helping the oaks ward off fungal infections and invasive insects. They also have a symbiotic relationship with humans, with archeological investigations finding that the Tarahumar of northern Mexico used powdered Flavoparmelia caperata to treat burns.
This lichen is interesting for these reasons, for the vast number of interconnections, biological, adaptational, and cultural, that this structure has within itself, with the "wild" ecosystem that surrounds it, and even with the humans who harvest it and use it medicinally.

Sources: http://www.radfordpl.org/wildwood/today/species_of_the_week/SOW32_greenshieldlichen.htm
http://www.californiaoaks.org/ExtAssets/OakLichensFinal.pdf

Publicado el 19 de marzo de 2014 por guiltyascharged