Phenotypic plasticity of primary thallus in selected Cladonia species (lichenized Ascomycota: Cladoniaceae)

The paper presents the results of comprehensive analyses concerning the phenotypic variability of the primary thallus in five chosen Cladonia species in relation to habitat conditions. Morphology and anatomy, as well as the cortex ultrasculpture, of primary squamules were examined in individual specimens from sunny and shady populations of each species. The Mann-Whitney U test and Principal Component Analysis (PCA) revealed several clear correlations between the type of habitat and the organisation of squamules. Significant differences refer mainly to anatomical features, especially to epinecral layer frequency and cortex thickness. On the contrary, examination of the surface ultrasculpture of squamules under SEM did not show any important differences between populations. Regardless of the habitat factors, a full range of cortical surface rugosity in samples from both habitats was noticed, and a high variability often refers to a singular squamule. The results indicate that some features are largely modified by environmental factors and/or depend on the development stage of individual specimens, and examination of these relationships should be the first step towards the evaluation of the taxonomic usefulness of the considered features.