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Role of basidiomycete yeasts in the lichen symbiosis
Jerhot, Štěpán ; Steinová, Jana (advisor) ; Černajová, Ivana (referee)
Lichens are, according to the latest definition considered ecosystems, which consist of a fungus, one or more photosynthesizing partners and an undefined number of additional microorganisms. The role of basidiomycete yeasts, which were shown to appear in many lichen species, has been discussed in the latest lichenological scientific papers. This bachelor thesis summarizes the knowledge about the distribution of lichen-associated yeasts and their importance in these symbioses. It also presents some of the methods newly used to study yeasts in lichen symbioses and compares the often inconsistent results based on the methods used in the papers. The topic is not sufficiently covered to draw sufficiently robust conclusions about the role of yeasts in lichen symbiosis. However, the results to date suggest that lichen yeasts do not have any significant specificity of association with mycobiont species, and there has been no support that yeasts directly enhance host fitness. A more detailed depiction of the structures that yeasts form at sites of contact with the host and a description of the mechanisms by which the participating partners communicate with each other could help to definitively determine their role in the lichen symbiosis.
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Complexity of lichen symbiosis
Černajová, Ivana ; Škaloud, Pavel (advisor) ; Palice, Zdeněk (referee) ; Spribille, Toby (referee)
Lichens are currently viewed as complex symbiotic systems. In addition to the main mycobiont and photobiont, a variety of associated fungi, bacteria and algae/cyanobacteria (minor/accessory photobionts) have been recognized. Their diversity has been intensively studied, but is still far from being fully apprehended. Likewise, recognition of the significance of the associated organisms to the whole system is still at the beginning but various crucial roles, from constitutive morphogenetic through physiological to various means of increasing the lichen's fitness, have already been suggested. The present thesis attempts to approach lichens in their full complexity. Focusing on two model systems; the Cladonia-Asterochloris association and ecologically delimited communities of Verrucariaceae; it aims: i) to examine patterns in photobiont choice and their relationship to lichen ecology; ii) to set a framework for in-vitro mycobiont-photobiont compatibility testing; iii) to explore the diversity of selected associated fungi and their possible relationships with the lichen host. We have shown that Verrucariaceae in the intertidal zone associate with largely understudied Ulvophycean photobionts. They mainly belong to Kornmanniaceae, Ulvales, and include a variety of novel lineages, one of which was...
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Biotic interactions in epiphytic lichen communities
Černajová, Ivana ; Svoboda, David (advisor) ; Peksa, Ondřej (referee)
The objective of my bachelor's thesis is to review available literature on biotic interactions in epiphytic lichen communities. At first the epiphytic habitat is defined. The next part deals with the interactions, specifically competition and predation. Lichens compete for light and space among each other and with other cryptogams at the same time. There are a few known mechanisms of competition, most of them being based on overgrowing of thalli and chemical action. Thallus morphology, growth rate and content of allelochemicals are the main traits determining success in competition. Competitive abilities depend on various abiotic factors as well as on total composition of the community. Lichens are forced to invest in chemical defence by the presence of herbivores and parasites. Distribution of the defence substances matches the optimal defence theory. There is numerous evidence that biotic interactions modify characteristics of both individuals and species, mainly considering the secondary metabolites content and the width of the realized ecological niche. Competitors and predators may determine species distribution. The thesis summarises the knowledge of the mechanism, character and impact of the competition and predation in epiphytic lichen communities. Key words: lichens, cryptogams, epiphytes,...
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Interaction of lichens and invertebrates with emphasis on mites
Vtípilová, Věra ; Steinová, Jana (advisor) ; Černajová, Ivana (referee)
Lichens interact with many groups of invertebrates. Acari (mites), Gastropoda (gastropods), Rotifera (rotifers), Nematoda (nematodes), Tardigrada (tardigrades), Protozoa (protists), Collembola (springtails) and Insecta (insects), especially Psocoptera (book and bark lice), Lepidoptera (butterflies and moths) and Coleoptera (beetles) represent the most common groups. These animals use lichens as a shelter and food. Lichens have different defence mechanisms, for example, secondary metabolites. On the other hand, invertebrates often mediate the dispersal of lichens. Some lichens can grow on shells or a body surface of living invertebrates. In my thesis, I describe individual groups of invertebrates that interact with lichens, and I mention specific examples of these interactions. A special emphasis is given on mites because they are one of the most important consumers of lichens, and I will pay attention to them in my diploma thesis.
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Mollusc grazing and secondary metabolites of lichens
Černajová, Ivana ; Svoboda, David (advisor) ; Vondrák, Jan (referee)
In contrast to the much that is known about herbivory and its consequences, lichenovory has seldom been studied. Recently, studies confirming the anti-feedant role of lichen secondary metabolites were brought out and hypotheses considering the nature of these interactions were introduced. Also, a few papers dealing with the ecological consequences of lichenovory were published lately. My thesis was aimed on the secondary metabolites issue and the preferences of the lichen feeders in the natural conditions. Six epiphytic lichen species containing secondary compounds (Parmelia sulcata, P. saxatilis, Parmelina tiliacea, Melanelixia glabratula, M. subaurifera, M. glabra), two without them (Melanohalea exasperata, M. exasperatula) and two species of gastropods that naturally climb the trees to feed on lichens (Lehmannia marginata, Cochlodina cerata) were selected for grazing experiments. The deterring role of the lichen compounds was proven. These were also identified using thin-layer chromatography. Subsequently, a transplantation experiment was carried out. It was focused on specifying the preferences of lichen grazers in their natural habitat. The genus Melanohalea that does not contain any secondary metabolites was strongly prefered. No significant preferences among the other species used in the...
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Biotic interactions in epiphytic lichen communities
Černajová, Ivana ; Svoboda, David (advisor) ; Peksa, Ondřej (referee)
The objective of my bachelor's thesis is to review available literature on biotic interactions in epiphytic lichen communities. At first the epiphytic habitat is defined. The next part deals with the interactions, specifically competition and predation. Lichens compete for light and space among each other and with other cryptogams at the same time. There are a few known mechanisms of competition, most of them being based on overgrowing of thalli and chemical action. Thallus morphology, growth rate and content of allelochemicals are the main traits determining success in competition. Competitive abilities depend on various abiotic factors as well as on total composition of the community. Lichens are forced to invest in chemical defence by the presence of herbivores and parasites. Distribution of the defence substances matches the optimal defence theory. There is numerous evidence that biotic interactions modify characteristics of both individuals and species, mainly considering the secondary metabolites content and the width of the realized ecological niche. Competitors and predators may determine species distribution. The thesis summarises the knowledge of the mechanism, character and impact of the competition and predation in epiphytic lichen communities. Key words: lichens, cryptogams, epiphytes,...
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