What is a Lichen?

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What is a Lichen?
by Mr Gordon Ramel

What is a Lichen ??
A lichen is a symbiosis. That means that it is two or more organisms living together such that both are more successful within the partnership than they would have been if they were living on their own. With lichens the basic components of this partnership are 1) a fungus called the 'mycobiont' and 2) one or more algae and/or a cyanobacteria called the 'photobiont'.

The true nature of the symbiosis between this two partners is still being debated by scientists and some would maintain that the fungus is a parasite on the photobiont. However, in many cases, the algae in question cannot survive alone in the habitat occupied by the lichen any more than the unattached fungi can, so it is not realistic to use the term parasite.

The fungal partners are mostly (over 95%) Ascomycetes. Most of the rest are Basidiomycetes. As far as science has been able to discover few if any of the fungi involved can survive and reproduce in the wild on their own. Each lichen species contains a different species of fungi and so it is according to the species of fungi that lichens are classified. This classification is generally based on characteristics of the thallus and reproductive organs. There are between 13500 and 17000 species of lichen depending on whose classification you believe. About 20% of fungal species are involved in lichen partnerships.

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