**4. The lichenized fungi: lichens**

Lichens are the most representative land group in Antarctica, despite they are not truly plants. They are formed by the symbiosis between a fungus plus an alga (most), a fungus plus a bacterium (case of *Leptogium puberulum,* as for example) or a fungus plus an alga and a bacterium (case of *Placopsis contortuplicata*). There are even lichenized mushrooms such as in *Lichenomphalia* spp. In the relationship, the photobiont provides the carbon source to the fungus, which can be polybasic alcohol (if it is green algae) or glucose (cyanobacteria). The fungus protects the algae from radiation and desiccation. The fungus still manages to reproduce in most cases through sexually formed spores or conidia (asexual), to fragments of the thallus or soredia. The algae reproduction is inhibited or suppressed [54].

To grow like a lichen, the spore needs to find the compatible algae that is rare in nature and lichenize. About 17,500 species of lichenized fungi and about 200 species of associated algae (100 green and 100 cyanobacteria) have been described. In this way, all of these fungi use algae in common and even different algae are used by the same species, in most cases even to adapt better to certain environments [55].

There are approximately between 386 to 427 species of lichens cited for Antarctica [55, 56] numbers that implies the most biodiverse group among terrestrials. In Antarctica in addition to the climate, limiting factors for lichens are the availability of substrate, which in most cases are rocks (in saxicolous species) or mosses (when species are muscicolous) and the presence of a source of nutrients, which can be originating from resting places or breeding animals, as already mentioned in the topic about mosses, above. These species are also starting competition with introduced ones which are being more and more frequent due climatic change.
