Alpine lichens as hot-beds of fungal diversification

Lichens are colonized by biologically and phylogenetically diverse additional fungi. According to their phenotypes these lichenicolous fungi have varying degrees of host specificity. We, however, think that the patterns of host specificity are insufficiently known and we hypothesize that many lichenicolous fungi also occur without expression of symptoms in other lichens beside their known hosts. We want to test this hypothesis in a lichen-rich habitat with a community-based approach. Alpine altitudes are characterized by vast lichen-dominated bio- surfaces, and our anticipated study area is particularly well known for its diversity of lichenicolous fungi. We will assess the diversity of lichen-associated fungi in lichen communities with culture-dependent and culture- independent microbiological methods. We will also compare fungal diversity in different parts of individual thalli. We will demonstrate that lichens play a prime role as reservoirs of fungal diversity and as a hot-bed of evolution. Lichens could represent evolutionary "ramps" for adaptation to other hosts.

Lichens are symbiotic, mutualistic associations between two main partners: an exabitant fungus, the mycobiont, and one or more populations of inhabitant photoautotrophic algae, the photobionts. Lichens are, however, colonized by biologically and phylogenetically diverse additional fungi. These additional fungi can occur conspicuously, symptom-developing, or cryptically in the lichen thalli (the body of the lichen) and can express varying degrees of host specificity. The symptom-developing lichenicolous fungi are species with poorly developed and often melanized mycelia and are usually recognized by their pathogenic symptoms and sexual or asexual spore-producing structures on the lichen hosts. The cryptically occurring lichenicolous fungi are detectable only when they are grown in axenic cultures. The symptom-developing lichenicolous fungi have been classified mainly according to their morpho-anatomical characters; little knowledge remains about the specificity patterns and the cryptic occurrence. Further, the phylogenetic relationships of the majority of them are completely unknown. Only recently, the molecular data obtained from the few available culture isolates and environmental samples of lichenicolous fungi were combined to confirmed their placement and uncover anamorph-teleomorph relationships. In our project we hypothesize that many symptom-developing lichenicolous fungi can also occur without expression of symptoms in other lichens beside their known hosts. To test our hypothesis we samples rock inhabiting lichens in an alpine lichen-rich habitat by applying a community-based approach. We estimated the species diversity of the symptom-developing licenicolous fungi and investigated the total fungal community diversity using molecular fingerprinting, phylogenetic and culture-based approaches. The study area included selected localities on the Koralpe Massiv (Austria), above the timber line, which are characterized by boulder homogeneously covered by lichen thalli infected or not by lichenicolous fungi Our sampling contributed to an increase of 17 symptom-developing lichenicolous fungal species for the studied region than previously known. The sampling proved successful to assess the nearly complete diversity of symptomatic lichenicolous fungi a well-defined niche. Likely, a similar sampling strategy applied to lichens would also raise the number of species and improve the biodiversity estimation in other regions.Cultured isolates and sequencing data showed that fungi retrieved from lichens are often closely related to fungi from different ecological niches and expressing diverse life styles. We concluded that the symbiotic structures of the lichen thalli appear to be a shared habitat of phylogenetically diverse stress-tolerant fungi, which seem to benefit from the lichen niche in otherwise hostile habitats. The isolated fungal strains represent now a valuable material for forthcoming analyses at genomic and chemical levels.