Format: ORAL

Pavel Skaloud1, Lucie Vancurova1, Veronika Vesela1, Zuzana Skvorova1, Jana Steinova1, Ivana Cernajova1, Patricia Moya2, Ondrej Peksa3

1 Department of Botany, Charles University, Prague, Czechia 2 Botánica, ICBIBE, Universitat de València, Valencia, Spain 3 Museum of West Bohemia in Pilsen, Pilsen, Czechia

Symbiotic organisms play a key role in natural communities. However, the mechanisms underlying the selection of symbiotic partners remain largely unknown. Over the past few years, we have aimed to understand the formation of lichen symbiotic associations by examining and comparing the diversity of endosymbiotic and free-living algae in the environment using a combination of eDNA metabarcoding and Sanger sequencing. In many cases, we revealed highly contrasting patterns of diversity, suggesting that the symbiotic inventory of lichen communities does not reflect the diversity of free-living algae. In particular, many symbionts that associate only with asexual lichen species have never been found at a site outside of lichen thalli, although various substrates, including aeroplankton, have been examined for the presence of free-living algae. Such findings strongly violate the paradigm of habitat-adapted symbiosis, as fungal hosts obviously do not select their algal partners from a regional pool of adapted species. Moreover, we hypothesize that some of the symbionts absent from the environment may exhibit a high degree of dependence on the presence of symbiotic fungi or may even represent obligate symbionts that never occur in the free-living state.