Antimicrobial action of usnic acid that is one of the most widely studied lichen secondary metabolite is caused by rapid and strong inhibition of RNA and DNA sy

The genetic diversity of photobionts in the lichen Protoparmeliopsis muralis was examined to determine the identity of the photobiont and the level of selectivity for the photobiont by the mycobiont. Forty ITS rDNA sequences of photobionts from thirty nine specimens of Protoparmeliopsis muralis have been determined. The photobiont species were identified both by direct comparison with the available sequences and by phylogenetic analysis. The sequences obtained from P. muralis specimens belonged to different Trebouxia clades. The most common photobionts were T. incrustata and an unidentified lineage, here named as “muralis I”. Less common photobionts were T. asymmetrica and T. gigantea. Two unidentified Trebouxia spp. and a photobiont that belonged to the clade that includes T. impressa, T. flava and T. potteri were also found to be associated with P. muralis. Such flexibility has not been reported to date. Moreover, two different photobionts were found in a single specimen. They belonged to the T. gigantea clade and “muralis I” lineage. The low level of selectivity with respect to the photobiont may constitute an important aspect in that Protoparmeliopsis muralis is one of the most successful urban lichens in the world.

Phylogenetic analyses using mtSSU and nuITS sequences of Buellia violaceofusca (previously placed in Lecanoromycetes), a sterile, sorediate lichen having a trebouxioid photobiont, surprisingly prove that the species is conspecific with Lecanographa amylacea (Arthoniomycetes), a fertile, esorediate species with a trentepohlioid photobiont. These results suggest that L. amylacea and B. violaceofusca are photomorphs of the same mycobiont species, which, depending on the photobiont type, changes the morphology and the reproduction strategy. This is the first example of a lichenized fungus that can select between Trebouxia (Trebouxiophyceae) and trentepohlioid (Ulvophyceae) photobionts. Trebouxia photobionts from the sorediate morphotype belong to at least three different phylogenetic clades, and the results suggest that Lecanographa amylacea can capture the photobiont of other lichens such as Chrysothrix candelaris to form the sorediate morphotype. Phylogenetic analyses based on rbcL DNA data suggest that the trentepohlioid photobiont of L. amylacea is closely related to Trentepohlia isolated from fruticose lichens. The flexibility in the photobiont choice enables L. amylacea to use a larger range of tree hosts. This strategy helps the lichen to withstand changes of environmental conditions, to widen its distribution range and to increase its population size, which is particularly important for the survival of this rare species.

Lecanora stainislai is characterized by a very thin sorediate thallus, forming a more or less continuous layer of soredia and by the production of usnic acid and zeorin. It usually grows on smooth bark of trees in forests and is known from the Czech Republic, Norway, Poland, Russia, Ukraine and western North America (Canada, USA). It is chemically similar to the sorediate L. compallens, which however has an episubstratal thallus in non-sorediate parts and often delimited soralia. They have also different phylogenetic positions within the L. symmicta group. Moreover, based on molecular marker analysis the position of L. expallens is resolved within this group for the first time.

The phylogeny of theMicarea prasinagroup was investigated using mitochondrial small subunit ribosomal DNA sequences from 14 taxa representing this group, four other members of the genusMicarea, andPsilolechia lucidaas an outgroup. A total of 31 new mtSSU rDNA sequences were generated, including 10 from theM. micrococcacomplex. Bayesian, maximum parsimony (MP) and maximum likelihood (ML) methods were used to analyse the data. The results show thatM. micrococcais not monophyletic and forms three strongly supported lineages: 1)M. micrococcas. str., 2)M. byssacea(Th. Fr.) Czarnota, Guzow-Krzemińska & Coppins comb. nov., and 3) a putative taxon that requires further studies.Micarea viridileprosais a sister species toM. micrococcas. str. and the recently describedM. nowakiiis a sister species toM. prasinas. str. The placement ofM. tomentosawithin theM. prasinagroup is confirmed.Micarea hedlundiiappears to be more closely related to theM. micrococcacomplex thanM. prasinas. str. Descriptions, illustrations, taxonomic remarks, distribution and habitat data forM. micrococcas. str. andM. byssaceaare provided. A lectotype forBiatora byssaceaHampe non Zwackh and a neotype forCatillaria prasinaβ [var.]byssaceaare selected.