When a fungus and an algae meet, an ecological success story is born: welcome to the fascinating world of lichens! And who would have thought that such a strange team could survive in extreme conditions, from freezing tundras to scorching deserts?”
- Convenient cohabitation
- Biological function of lichens
- Lichens and climate change
- Curiosities and species
Convenient cohabitation
Lichens are complex organisms resulting from thesymbiotic association between a fungus and an alga or cyanobacterium.
This mutualistic relationship allows them to colonise extreme environments where neither the fungus nor the algae could survive on their own.
Their structure depends on the species involved and is composed of three main layers:
- Upper layer: consisting of compact protective fungal cells
- Median layer: contains the cells responsible for photosynthesis
- Bottom layer: formed by fungal hyphae that anchor to the substrate.
They are extremely adaptable and can be found in a wide range of habitats, from deserts to polar regions.
They can reproduce either sexually through the production of fungal spores, or asexually through thallus fragmentation or the formation of outgrowths containing both symbiotic partners.
Biological function of lichens
Lichens are extraordinary organisms that play multiple essential roles in ecosystems.
They contribute to soil formation by decomposing rocks through the production of acids, thus facilitating the creation of fertile soil and allowing other plants to grow.
They provide habitat and food for a variety of organisms, such as insects, birds and small mammals.
In arid environments, they play a role in soil protection, helping to stabilise the soil and preventing erosion.
In addition, some species are used in the production of natural dyes, perfumes and traditional medicines.
Lichens and climate change
They are excellent indicators of climate change due to their sensitivity to changes in temperature, humidity and air quality.
Some have a limited capacity to adapt rapidly to climate change; they have a low capacity for migration and dispersal, which makes them particularly vulnerable.
Climate change can affect the distribution and biodiversity of lichens, altering habitats and growing conditions, and leading to a reduction in diversity in some areas.
They play a crucial role in the soil cycle, modifying nutrient availability.
Finally, they can adapt to environmental stress due to climate change by modifying gene expression, helping some species to better tolerate the new conditions.
Curiosities and species
These organisms are capable of surviving in extreme environmental conditions, with temperatures ranging from -200°C to +100°C.
They grow very slowly, often only a few millimetres per year, and some can live for hundreds or even thousands of years.
The best known species are:
- Wood beard (Usnea spp.): widespread in the mountains, it has a filamentous thallus that hangs from tree branches, especially from larches.
- Reindeer lichen (Cladonia rangiferina): with a branched, bushy thallus, it forms the typical vegetation of tundras and is an essential winter food for reindeer.
- Crusty lichen (Lecanora spp.): adheres tightly to the substrate, such as rocks or bark, forming a thin, compact crust.
- Leafy lichen (Parmelia spp.): has a flattened, lobed thallus that grows parallel to the substrate, often on tree trunks and branches.
- Fruciferous lichen (Evernia prunastri): with a branched, bushy thallus, it is often used in perfume production for its characteristic aroma.
In some cultures, they are symbols of endurance and longevity, due to their ability to survive in harsh environments and their long lifespan.
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