This thesis is focused on the diversity of lichen photobionts and its relation to the mycobionts and environmental factors. The key objective is to map the diversity of lichen photobionts of the genus Stereocaulon, which has been insufficiently examined in comparison with related lichens Cladonia and Lepraria. In total, 92 samples belonging to 12 species of genus Stereocaulon were examined, being found in four continents, at the altitude of 50 to 2 900 metres a. s. l., and variety of natural and artificial substrata. Phylogenetic analyses were inferred on the basis of ITS rDNA, actin type I, 18S rDNA and rbcL sequences. Photobionts belonging to two unrelated genera within Trebouxiophyceae, Asterochloris and Chloroidium, were found in thalli of Stereocaulon lichens. While Asterochloris represents one of the most frequent photobionts of various lichens, Chloroidium has been until now recorded as a lichen photobiont very rarely. The content of heavy metals in substratum can be considered as a determinative factor for its occurrence. A new lineage affiliated to genus Asterochloris was discovered on the island La Palma (the Canary Islands). Interestingly, none of common, widespread Asterochloris lineages has been found in this locality. The lichen photobionts of the genus Stereocaulon were discovered in 12 of...

This diploma thesis was focused on the community ecology of corticolous subaerial cyanobacteria and algae. Altogether 54 morphotypes were identified on the surface of the tree bark in the Nature Reserve Březina in České středohoří Mts., Czech Republic. Compared to publish data on tropical and subtropical habitats, high morphological diversity of these organisms in a temperate region was thus recognized. Coccoid green algae - most of them belonging to the class Trebouxio-phyceae - dominated. In a study focused on the algae community structure at small spatial scales (such as a single tree trunk), the temporal factors were found as the most important factor influencing the species composition. The height of a sample on trunks and type of bark roughness seemed to influence the species richness, yet the differences were not significant. The alpha-diversity and species composition of corticolous algal communities among individual trees were strongly influenced by host tree species. The pH of the bark surface also had significant impact on species composition. Generally, trees with lower pH of the bark surface (alder, spruce) had lower species richness, whereas trees with more alkaline bark surface (ash, beech, maple) had higher alpha-diversity values. Considering the generally efficient dispersal ability of...

The aim of this diploma thesis was to reveal the taxonomic position and phylogenetic relationships of the dominant planktonic algae in two acid metal-rich lakes (Hromnice Lake and Plešné Lake, Czech Republic) and to compare these isolates with other closely related strains with the focus on the tolerance to various toxic metals (Cr, Al, Cu, Mn, Zn, Hg). The phylogenetic analyses showed that both strains belong to species Coccomyxa simplex. It was the first evidence that specifically this species is capable to become the dominant phytoplankton alga in the extreme environment of acid lakes with increased supply of phosphorus. Based on 18S rDNA analysis, four independent phylogenetic lineages were revealed within the genus Coccomyxa with three of them containing isolates from acid freshwaters. Furthermore, new strains of the recently described species Coccomyxa polymorpha were found growing in various chemical solutions. The toxicity test revealed that Coccomyxa simplex strains isolated from Hromnice and Plešné lakes did not show any peculiar resistance to increased metal concentrations. A significantly strain-specific response was recorded in case of aluminum, however, it was not related to the concentration of this metal in the original habitat. The ability to thrive in extreme habitats is probably...