The diversity and phylogenetic position of photobionts in the widespread saxicolous, crustose lichen-forming ascomycete Lecanora rupicola s.l. is presented. The algal partners of this lichen species complex belong to diverse and unrelated lineages in the genus Trebouxia . Specimens were sampled from different habitats and geographical origins. Either whole thallus DNA extractions or minute fragments of the algal layer of the lichen thallus were subjected to polymerase chain reaction, using primers that specifically amplify internal transcribed spacer rDNA of the photobionts. No correlations between different chemical races of L. rupicola with particular lineages of Trebouxia spp. were found. Irrespective of the different algal partners, all lichen thalli abundantly developed ascomata. L. rupicola apparently maintains full fecundity with a low degree of selectivity for photobionts, which promotes the occurrence of this lichen-forming species in ample ecological situations.

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A first assessment of paralogy in non-reducing polyketide synthases of Parmeliaceae is presented. Primers which are specific to the keto-acyl synthase domain were used to amplify gene fragments of putative non-reducing polyketide synthases from various representatives of the family. The corresponding sequences were analysed together with a selection of known polyketide synthase genes from other fungi, including lichenized fungi. The results suggest that genes from Parmeliaceae represent at least 6 paralogs. Their different positions in the tree partly correlate with the variable presence of spliceosomal introns at particular positions in the gene fragments. Because only one paralog could be unambiguously detected in each species by direct sequencing of PCR products with this approach, we tested the applicability of clade-specific primers, designed by using orthologous signature sequences. With these primers more paralogs could be detected from the same DNA extract in a number of species, but certain paralogs were consistently not amplified in these species. The paralog-specific primer approach can potentially be used for a rapid screening of PKS genes from a broader range of lichen fungi.

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A phylogenetic analysis of the Lecanora rupicola group based on combined nITS rDNA and beta-tubulin sequences and a combined dataset of ITS, beta-tubulin and partial sequences of polyketide synthase genes reveals a previously unrecognized species, which here is introduced under the name Lecanora bicinctoidea. The new species is a sister group of the L. swartzii complex (including L. swartzii and L. lojkaeana), which is characterized by eucorticate ascomata, and a morphological diversity that includes also a dwarf-fruticose lineage. The preferential occurrence on vertical to overhanging siliceous rocks corresponds more closely to L. swartzii. A detailed investigation of phenotypic characters reveals that the new species differs from the superficially similar morphospecies L. bicincta in several ways, such as a thallus of comparatively small areoles and broadly sessile ascomata and the development of an amphithecial cortex devoid of algal remnants (i.e. an eucortex). L. bicinctoidea contains methyl 3alpha-hydroxy-4-O-demethylbarbatate, a chemical compound not known from other members of the L. rupicola group. We also discuss the importance of eucortex formation as one of several factors that are involved in the evolution of substrate-detached thallus structures.