Substratum preference of two species of Xanthoparmelia

A Review of Laboratory Requirements to Culture Lichen Mycobiont Species

Lichens are symbiotic associations between fungi (the mycobiont) and algae or cyanobacteria (the photobionts). They synthesize a large number of secondary metabolites, many of which are potential sources of novel molecules with pharmacological and industrial applications. The advancement of in vitro culture methods of lichen-forming fungi would allow the comprehensive application of these compounds at large scales, enable improvements in the synthesis, facilitate understanding of the role of the partners in the synthesis of these compounds and increase our knowledge about the genes associated with secondary metabolites production. The aim of this work is to summarize the nutritional and physicochemical requirements that have been used to date to culture different lichen-forming fungi species. In total, the requirements for the cultivation of 110 species are presented. This review can provide a starting point for future experiments and help advance the methods of culturing lichenized fungi. The type of diaspore selected to isolate the mycobiont, the composition of the isolation and culture media and the corresponding physicochemical parameters are essential in designing an efficient lichen culture system, allowing the achievement of a suitable growth of lichen-forming fungi and the subsequent production of secondary metabolites.

Morphology and secondary chemistry in species recognition of Parmelia omphalodes group - evidence from molecular data with notes on the ecological niche modelling and genetic variability of photobionts

To evaluate the importance of morphological and chemical characters used in the recognition of species within the Parmelia omphalodes group, we performed phylogenetic, morphological and chemical analyses of 335 specimens, of which 34 were used for molecular analyses. Phylogenetic analyses, based on ITS rDNA sequences, show that P. pinnatifida is distinct from P. omphalodes and the most important difference between those species is the development of pseudocyphellae. In P. pinnatifida, they are mostly marginal and form white rims along lobes margins, but laminal pseudocyphellae can develop in older parts of thalli and are predominantly connected with marginal pseudocyphellae. In contrast, in P. omphalodes laminal pseudocyphellae are common and are predominantly not connected to marginal pseudocyphellae. Chemical composition of secondary lichen metabolites in both analysed species is identical and therefore this feature is not diagnostic in species recognition. Few samples of P. discordans, species morphologically similar to P. omphalodes and P. pinnatifida, were also included in the analyses and they are nested within the clade of P. omphalodes, despite the different chemistry (protocetraric acid present versus salazinic acid in P. omphalodes). All taxa of the P. omphalodes group occupy similar niches, but their potential distributions are wider than those currently known. The absence of specimens in some localities may be limited by the photobiont availability. Parmelia omphalodes and P. pinnatifida are moderately selective in photobiont choice as they form associations with at least two or three lineages of Trebouxia clade S. Parmelia pinnatifida, as well as P. discordans are associated with Trebouxia OTU S02 which seems to have a broad ecological amplitude. Other lineages of Trebouxia seem to be rarer, especially Trebouxia sp. OTU S04, which is sometimes present in P. pinnatifida. This study indicates the importance of extensive research including morphology, chemistry and analysis of molecular markers of both bionts in taxonomical studies of lichens.