Flechten. Der Erfolg einer Symbiose

The success of a symbiosis: Lichens Lichens are a unique group of organisms composed of one or two alga and a fungus. Together they form species specific thalli. Their common eco‐physiological properties allow colonizing almost all terrestrial habitats, even the most hostile climatic zones on earth. However, as poikilohydrous organisms they also suffer from disadvantages related with their nature. As water content cannot be actively controlled, many lichens experience water‐oversaturation, thus being not able to gain full photosynthetic rates, even though they have otherwise optimal conditions. These eco‐physiological properties set up the frame for which microclimatic situation the realized thallus construction might do best. As all optimizations regarding water uptake also count for water loss, lichens are always at the edge of having either too much or not enough water for optimal carbon gain. So each habitat has its own challenge for the lichen thallus construction and lichens have to fit well into a specific ecological niche.