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Biogeography and specificity of Asterochloris photobionts
Řídká, Tereza ; Škaloud, Pavel (advisor) ; Vondrák, Jan (referee)
This diploma thesis has focused on the diversity and biogeography of Asterochloris photobionts. Since no study so far has been published on the biogeography of symbiotic microorganisms, the presented thesis is the first attemp to trace the biogeographic distribution and endemism of symbionts. By gathering 121 Asterochloris sequences obtained from lichen thalli sampled outside Europe and America, the diversity within the genus increased dramatically. The phylogenetic analysis based on the concatenated alignment of ITS rDNA and actin sequences obtained from Cladonia and Stereocaulon photobionts revealed 28 differently supported clades. Of them, eight lineages were newly discovered. Three environmental factors explaining the best the distribution pattern of Asterochloris photobionts were selected according to the statistical tests of the phylogenetic signal: two different types of biogeographical ecoregions and the substrate type. In general, the genus Asterochloris is distributed cosmopolitally, with a very low rate of endemism. Newly obtained data indicate that the restricted distribution of any photobiont clade is not caused by either historic or biological factors, but more likely by specific climatic or habitat preferences.
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Photobiont diversity in the lichen genus Stereocaulon (Lecanoromycetes, Ascomycota)
Vančurová, Lucie ; Škaloud, Pavel (advisor) ; Peksa, Ondřej (referee)
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...
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