Dispersal is a process of fundamental importance for the spatial dynamics, evolution and survival of populations. Despite its significance, it remains poorly understood in many organisms. Lichen partners disperse either individually via fungal sexual spores and algal cells or by clonal propagules that include both partners. Because of their reduced size, aposymbiotic sexual propagules appear to be considerably more adjusted for long distance dispersal. As a result, algal cells and fungal ascospores are among the most common airborne biological particles, with clonal propagules being less prevalent (Tormo et al. 2001). Up to this point, most estimates of lichen dispersal capacity have been made indirectly, i.e., by analysing the spatial arrangement of colonized trees, modeling techniques, or population genetic studies of a few model species. Direct investigations of airborne lichen propagules are uncommon and rely primarily on morphological determination of trapped particles (Tormo et al. 2001; Marshall 1996). While sexual propagules allow for effective dispersal, their future establishment is at risk since germinating fungal spores need to obtain appropriate algae from the environment in order to form a new lichen. Recent research, however, demonstrates divergent diversity patterns across endosymbiotic and free-living algal populations. In some cases, suitable algal symbionts are completely absent from the environment (Vančurová et al. 2020). The formation of vegetative propagules, in theory, should circumvent such problems. However, there is some indication that symbiotic algae are rejected and exchanged for algae from the local pool during the early phases of vegetative propagule development (Ohmura et al. 2006). The objective of this PhD project is to increase our understanding of lichen dispersal an establishment.
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