The algal partners in lichens can be found living on their own in nature, as free-living species in their own right.The fungal partners in British lichens are recognizable Ascomycetes or Basidiomycetes.
Unlike other fungi or indeed their algal partner, they cannot survive on their own. Interestingly, the same alga can combine with different fungi to produce entirely different lichens.The same fungus can also form different lichens depending on the type of alga which it associates with.Most lichens contain only one kind of alga, but some may contain two.Identifying the type of alga in a lichen may be difficult, as they frequently look different to the free-living forms.Lichens present a very intriguing problem for people whose job is to name different kinds of organisms.This is because a lichen is not a separate organism in the sense of being one type of individual.
It is actually a close partnership between a fungus and an alga. The two types of organisms in the partnership are so closely interwoven that they appear as a single individual.
This individual looks entirely different to either of the partner organisms making up the structure.
Lichens are distinctive and they form many different, recognizable types.
Many of these have been given specific names of their own, despite the fact that each lichen is already a mixture of different species.
There are more than 1,700 species of lichen in Britain.
Approximately 18,000 species of lichen have been described and identified worldwide.