Ecological role of lichens
Ecological role of lichens
Lichens are symbiotic organisms resulting from the association of two individuals: an autotrophic organism (a cyanobacterium or an algae – mostly a chlorophyte) and a heterotrophic organism (a fungus, generally an ascomycete or a basidiomycete).
Lichens are organisms characterized by a thallus and are classified based on the taxonomy of the fungal species (in previous classifications they were part of the cryptogams).
In lichens the two symbionts coexist to mutual advantage: the heterotrophic fungus survives thanks to the organic compounds produced by the photosynthesis of the cyanobacterium or algae, while the latter receives protection, mineral salts and water in exchange. The evolution of lichenization is probably very ancient and did not occur from a monophyletic group of lichenized fungi. Lichenization has evolved independently in numerous groups, a hypothesis also supported by recent molecular studies.
The true symbiotic nature of these organisms was recognized only in 1867 by Simon Schwendener.
Ecology –
Lichens contribute significantly to global biodiversity.
Lichen diversity is also among the highest in Europe with 2345 species representing approximately 14.4% of the world’s lichen diversity (Convention on Biological Diversity, 2005; Nimis & Martellos, 2008).
This is why their protection is important in the context of natural and agroforestry systems.
Lichens are extremely adaptable organisms, found in almost every environment on Earth. They are considered the dominant plant life form on 8% of the Earth’s surface. On volcanoes, mountains, glaciers, in deserts or in Antarctica they manage to survive where plants do not grow.
Lichens are often used by birds to build nests or as a habitat for some invertebrates.
They are an important source of food for animals: from the smallest insects to large Arctic reindeer.
They are essential for many ecosystem functions: such as nitrogen fixation,
primary production and the water cycle.
The study of lichens is of increasing importance as a series of functions are associated with them.
– They are important for the ecosystem;
– They produce particular molecules (sometimes used in cosmetics);
– They are excellent bioindicators. Used for air biomonitoring.
Lichens are life forms that are extremely sensitive to air pollution.
In fact, lichens involuntarily absorb pollutants both in gaseous form and in the form of dust.
They do not provide mechanisms for getting rid of old or contaminated parts.
They have a slow metabolism and are long-lived. A lichen grows a few centimeters each year. Their study can allow us to have information over very long periods.