To evaluate the importance of morphological and chemical characters used in the recognition of species within theParmelia omphalodesgroup, 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 thatP. pinnatifidais distinct fromP. omphalodesand the most important difference between those species is the development of pseudocyphellae. InP. 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, inP. omphalodeslaminal 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 ofP. discordans, species morphologically similar toP. omphalodesandP. pinnatifida, were also included in the analyses and they are nested within the clade ofP. omphalodes, despite the different chemistry (protocetraric acid present versus salazinic acid inP. omphalodes). All taxa of theP. omphalodesgroup 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 omphalodesandP. pinnatifidaare moderately selective in photobiont choice as they form associations with at least two or three lineages ofTrebouxiaclade S.Parmelia pinnatifida, as well asP. discordansare associated withTrebouxiaOTU S02 which seems to have a broad ecological amplitude. Other lineages ofTrebouxiaseem to be rarer, especiallyTrebouxiasp. OTU S04, which is sometimes present inP. 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.
