This review discusses the production of reactive oxygen species (ROS) by lichens and their possible roles. All organisms produce ROS, and production is increased by many abiotic and biotic stresses. Intracellular ROS production is generally considered to be harmful, and a variety of enzymic and non-enzymic scavenging systems exist to detoxify them. However, extracellular ROS formation has been suggested to play ‘positive roles’, particularly in the response of organisms to stress. Given their high stress tolerance, it is rather surprising that studies on extracellular ROS production by lichens have just started. Surveys of a wide range of lichens have shown that constitutively high rates of extracellular superoxide production occur in the Suborder Peltigerineae, but production appears to be absent in other groups. In some members of the Peltigerineae ROS production is stimulated by desiccation and wounding. It seems probable that the enzymes that produce the superoxide are laccases, based on first the types of substrates that lichens can break down, and second the dependence of the breakdown of these substrates on pH, temperature and the presence of inhibitors. While much more work is needed, we suggest that physiological roles of extracellular ROS production will be found to include defence against pathogens, melanization, and lignin breakdown.

Fuscopannaria atlantica P. M. Jørg. & P. James, a new species from consolidated soil near the sea is described from the Azores. It is also present in SW Ireland, S W England, Wales and SW Scotland and appears to be part of the Macaronesian element in the lichen flora of the British Isles, as well as an addition to the oceanic flora of Liguria, Italy. An updated key to the European species of Fuscopannaria is also presented.

Lecidea hercynica Hauck & Schmull is described as a new species from Germany. It is characterized by a poorly developed or bullate to verrucose, areolate thallus on whitened spots of the substratum, numerous plane to yellowish brown to black, convex apothecia with a persistent margin, Micarea type-like asci, and by the presence of atranorin and protocetraric acid. It does not belong to Lecidea s. str., but is provisionally placed in Lecidea s. lat. until a taxonomic treatment of the whole group has been carried out. Lecidea hercynica is widespread in high-elevation forests of Picea abies in the Harz Mountains, where it grows preferably on decorticated wood in open situations.

Molecular phylogenetic analyses based on nuclear ITS rDNA and mitochondrial SSU rDNA sequences from 32 specimens representing Parmotrema pseudoreticulatum, P. reticulatum and P. clavuliferum from Africa, Asia, Australia, and Europe are reported. Samples from western Europe and South Africa formed an independent monophyletic group, which belongs to P. pseudoreticulatum, a species not accepted by some recent authors, that has only been reported from Portugal, Spain and Morocco. In contrast, P. reticulatum and P. clavuliferum, both widely distributed taxa, formed a monophyletic clade, supporting the synonymy already proposed on the basis of morphological features.

Eight species of the lichen genus Pertusaria (Pertusariaceae) are reported from the Juan Fernández Archipelago (Chile). Pertusaria fernandeziana is described as a new species and two species, Pertusaria phlyctaenula Nyl. and Pertusaria dehiscens Müll. Arg., are recorded for the first time from the archipelago. Range extensions of the known distribution within the archipelago are reported for Pertusaria hadrocarpa Zahlbr., Pertusaria melanospora Nyl., Pertusaria pachythallina (Räsänen) Messuti, Pertusaria papillulata Nyl., and Pertusaria velata (Turner) Nyl. Pertusaria polycarpa Kremp. var. monospora Zahlbr. is reduced to synonymy with Pertusaria papillulata and Pertusaria chilena Zahlbr. is synonymized with Pertusaria velata. A diagnostic key, descriptions, and illustrations of the species are presented with data on their habitat ecology and distribution.

The family Stictidaceae (Ostropales, Ascomycota) contains both lichenized and non-lichenized fungi. Here, we test if Conotrema (lichenized) and Stictis (non-lichenized) as currently delimited are distinct monophyletic genera, by parsimony and parsimony jackknifing analyses of combined nuclear rDNA (ITS and partial LSU rDNA) and mitochondrial SSU rDNA sequence data matrices. The study includes four species of Stictis, three species of Conotrema, and representatives of the related Schizoxylon (lichenized), Odontotrema, Carestiella (at least sometimes associated with algae), Cryptodiscus and Thelotrema (lichenized). In all analyses, the Conotrema species were nested within Stictis with high support. Thus, we conclude that Conotrema are only lichenized representatives of Stictis. The type species of the two generic names, C. urceolatum and S. radiata, are sister taxa in our analyses. Furthermore, the analysis gave no support for the present infrageneric classification of Stictis. Carestiella socia (the type of Carestiella) and the two representatives of Schizoxylon studied were also nested within Stictis s. lat. The Odontotremataceae is the sister group to the Stictidaceae, and Cryptodiscus foveolaris groups with Thelotrema rather than with the Stictidaceae. We conclude that lichenization in the Stictidaceae does not characterize natural groups, and that Conotrema should be considered a synonym to Stictis, as predicted by anatomical characteristics. The new combinations Stictis urceolatum and Stictis populorum are made.

Heppia arenacea M. Schultz and Lempholemma polycarpum M. Schultz are described as new and placed in the Lichinaceae. Heppia arenacea occurs in soil-crust communities in southern Yemen and on Socotra. It colonizes both calcareous soil-crusts over limestone as well as soils originating from basaltic rocks. The sand-coloured, squamulose thallus, the erumpent, dark red apothecia and the incorporation of soil material into the thallus are diagnostic characters. Lempholemma polycarpum occurs on inclined limestone boulders in south-eastern Yemen. It is characterized by an umbilicate-lobate thallus with radiating, tongue-shaped, furcate lobes which bear numerous, small, immersed apothecia with punctiform discs.

Decreasing abundance of epiphytic lichens with increasing Mn supply from the substratum or from stemflow was found in several coniferous forests of Europe (Germany) as well as western (Montana, British Columbia) and eastern North America (New York State). Experiments carried out with Hypogymnia physodes and other species of chloro- and cyano-lichens suggest that these correlations are causal. High Mn concentrations e.g. reduce chlorophyll concentrations, chlorophyll fluorescence and degrade the chloroplast in lichen photobionts. Excess Mn inhibits the growth of soredia of H. physodes and causes damage in the fine- and ultra-structure of the soredia. Adult lichen thalli remain structurally unaffected by Mn. Manganese uptake does not result in membrane damage. Calcium, Mg, Fe and perhaps also Si alleviate Mn toxicity symptoms in H. physodes. Lecanora conizaeoides is not sensitive to Mn in laboratory experiments or in the field. The data suggest that high Mn concentrations are an important site factor for epiphytic lichens in coniferous forests that until recently has been overlooked. Manganese reaching the microhabitat of epiphytic lichens is primarily soil-borne and is usually not derived from pollution.

Tetramelas phaeophysciae, a new obligately lichenicolous species occurring in Scandinavia, Iceland and Greenland, is described, and the closely related Buellia pulverulenta, together with B. triphragmioides, are transferred to Tetramelas. Phylogenetic reconstructions based on sequence data from nITS1-5.8S-ITS2 rDNA, using Bayesian inference and parsimony analyses, support the segregation of the new species from B. pulverulenta as well as the segregation of Tetramelas and Diplotomma from Buellia s. str.

Descriptions are provided for two new species, Mycomicrothelia lateralis Sipman from Norfolk Island and M. triangularis Aptroot from Puerto Rico, both characterized by lateral ostioles and uniseriate ascospores. Based on the examination of additional fresh material, the genus Ornatopyrenis is included in Mycomicrothelia and the new combination Mycomicrothelia queenslandica (Müll. Arg.) Sipman & Aptroot is made. Ornatopyrenis muriformis Aptroot is proposed as a synonym of M. decipiens (Müll. Arg.) R. C. Harris.

Nimisia deusta, based on Parmelia enteromorpha var. deusta, is shown to be the correct name for the species currently known as N. fuegiae. Original material collected by J. D. Hooker in 1842, and collections made by Henry Imshaug between 1968 and 1971, have shown that the species is more widely distributed than previously reported, being known throughout the southern tip of South America (Argentina: Isla Grande de Tierra del Fuego, Isla de los Estados; Chile: Cape Horn Islands; Falkland Islands), that it has a uniform secondary metabolite chemistry of fumarprotocetraric acid in the upper medulla (not lacking lichen substances as previously reported), and that it is not uniformly black but has a partly pale brown upper cortex.

The phylogeny of the lichen family Gomphillaceae sensu Vězda & Poelt was reconstructed by parsimony analysis of a phenotype data matrix including ecological, thallus, apothecial, and hyphophore characters. Two hundred and twenty-eight taxa and 209 characters, grouped into ecology (14), thallus (45), apothecia (83), and hyphophores (67), were included in the analysis. Gyalidea hyalinescens (Asterothyriaceae) was used as outgroup. Because of the high level of homoplasy (consistency index of all-taxa tree without character weighting CI=0·12), and the resulting uncertainty (generally low support) with respect to group topologies, we accepted both monophyletic clades and paraphyletic grades and only rejected previously proposed classifications if the taxon in question appeared polyphyletic, or if segregate taxa were characterized by functionally independent apomorphies and/or by evidence of radiation. Thus, the following 19 genera (synonyms in brackets) are accepted as a result of this study: Actinoplaca (segregate of Echinoplaca; isidioid hyphophores), Aderkomyces (Psathyromyces; segregate of Tricharia; white setae, hyphal excipulum), Aplanocalenia (segregate of Calenia; immersed applanate apothecia), Arthotheliopsis (Phallomyces; segregate of Echinoplaca; smooth thallus, differentiated diahyphae), Aulaxina (Lochomyces; carbonized apothecia, bristle-shaped hyphophores with palmate diahyphae on prothallus), Calenia (Bullatina; zeorine apothecia, acute to bristle-shaped hyphophores with moniliform diahyphae), Caleniopsis (thick white thallus with dark prothallus, zeorine apothecia, bristle-shaped hyphophores with palmate diahyphae on prothallus), Diploschistella (segregate of Gyalideopsis; immersed apothecia), Echinoplaca (Spinomyces, Sporocybomyces; crystalline thallus, acute to bristle-shaped hyphophores with moniliform or derived diahyphae), Ferraroa (segregate of Gyalideopsis; campylidioid hyphophores), Gomphillus (vertically elongate apothecia, filiform ascospores), Gyalectidium (Tauromyces; zeorine apothecia, squamiform hyphophores), Gyalideopsis (Epilithia, Microlychnus, Microspatha; chiefly biatorine apothecia, setiform or flabellate hyphophores), Hippocrepidea (applanate apothecia, squamiform hyphophores with strongly derived diahyphae), Jamesiella (segregate of Gyalideopsis; isidioid hyphophores), Lithogyalideopsis (segregate of Gyalideopsis; lecideine apothecia, bristleshaped hyphophores with palmate diahyphae), Paratricharia (black setae, partly carbonized apothecia with columella), Rubrotricha (segregate of Tricharia; red-brown setae, hyphal excipulum), and Tricharia (Microxyphiomyces, Setomyces; black setae, proso- or paraplectenchymatous excipulum). The following taxa and combinations are introduced: Actinoplaca gemmifera comb. nov. [Echinoplaca gemmifera], Aderkomyces albostrigosus comb. nov. (Tricharia albostrigosa), A. armatus comb. nov. (T. armata), A. carneoalbus comb. nov. (T. carneoalba), A. cretaceus comb. nov. (T. cretacea), A. cubanus comb. nov. (T. cubana), A. deslooveri comb. nov. (T. deslooveri), A. dilatatus comb. nov. (T. dilatata), A. fumosus comb. nov. (T. fumosa), A. heterellus comb. nov. (Arthonia heterella; Lopadium membranula; Echinoplaca affinis), A. guatemalensis comb. nov. (T. guatemalensis), A. lobulimarginatus sp. nov., A. microcarpus comb. nov. (T. microcarpa), A. microtrichus comb. nov. (T. microtricha), A. papilliferus comb. nov. (T. papillifera), A. planicarpus comb. nov. (T. planicarpa), A. planus comb. nov. (T. plana), A. purulhensis comb. nov. (T. purulhensis), A. ramiferus comb. nov. (T. ramifera), A. subalbostrigosus comb. nov. (T. subalbostrigosa), A. subplanus comb. nov. (T. subplana), A. testaceus comb. nov. (T. testacea), A. verruciferus comb. nov. (T. verrucifera), A. verrucosus comb. nov. (T. verrucosa), Aplanocalenia gen. nov., A. inconspicua comb. nov. (Heterothecium inconspicuum; Calenia inconspicua), Arthotheliopsis serusiauxii comb. nov. (Echinoplaca serusiauxii), A. tricharioides comb. nov. (E. tricharioides), Caleniopsis aggregata comb. nov. (Calenia aggregata), C. conspersa comb. nov. (Thelotrema conspersa; Calenia conspersa), Diploschistella lithophila comb. nov. (Gyalideopsis lithophila), D. solorinellaeformis comb. nov. (G. solorinellaeformis), D. trapperi comb. nov. (G. trapperi), Echinoplaca macgregorii comb. nov. (Arthonia macgregorii), Ferraroa gen. nov., Ferraroa hyalina comb. nov. (Gyalideopsis hyalina), Gyalideopsis brevipilosa comb. nov. (Tricharia brevipilosa), G. buckei nom. nov. (Tricharia vezdae), G. cristata comb. nov. (Epilithia cristata), G. glauca comb. nov. (Microspatha glauca), G. puertoricensis sp. nov., Jamesiella gen. nov., J. anastomosans comb. nov. (Gyalideopsis anastomosans), J. perlucida comb. nov. (G. perlucida), J. scotica comb. nov. (G. scotica), Lithogyalideopsis gen. nov., L. aterrima comb. nov. (Gyalideopsis aterrima), L. poeltii comb. nov. (G. poeltii), L. vivantii comb. nov. (G. vivantii), L. zeylandica comb. nov. (G. zeylandica), Rubrotricha gen. nov., R. helminthospora comb. nov. (Tricharia helminthospora), R. subhelminthospora sp. nov., Tricharia atrocarpa sp. nov., and Tricharia variratae sp. nov. A key is presented to all genera of Gomphillaceae, and a synopsis of the family classification, with all presently known species, is provided.

The new genus Lambinonia Sérus. & Diederich is introduced for the lichenicolous hyphomycete Melanconium strigulae Elenkin & Woron. This species forms dark sporodochia on the surface or at the margin of the thalli, or extruding out of the perithecia and pycnidia of the foliicolous Strigula buxi, S. nemathora and S. nitidula. It is so far known from the western Caucasus (Georgia and Russia), southern Italy, Tenerife (Canary Islands), St-Lucia (West Indies), and Burundi and Rwanda in Africa. The new combination Lambinonia strigulae (Elenkin & Woron.) Sérus. & Diederich is introduced and a neotype collection is designated.

Terricolous lichens are the dominant vegetation in expansive areas of the Namib Desert, where fog is the main source of moisture and other vegetation is scarce. They play several important roles in soil crust stabilization and in the primary production of the Namib Desert ecosystem, yet little is known about the diversity and distribution of lichens in the northern unexplored regions of the Namib. To our knowledge, this study is the first survey of terricolous lichens to be carried out in the northern Namib Desert. Seven soil crust habitat types were identified in the study area, and a total of twenty-eight soil crust lichen species was recorded. The survey uncovered lichen species that may be unique to the northern Namib, including vagrant species, and common species were frequently found in a vagrant form. The crustose group was the most widely represented. Overall community compositions differed from those found in other regions of the Namib, and distribution patterns suggest a link to gravel clast size and physical soil crust type.

The Tabernas badlands in semiarid south-east Spain is one of the driest regions in Europe with a mean annual precipitation of c. 240 mm. The landscape is deeply dissected, with canyons, ramblas and sparsely vegetated eroded badland slopes. The vegetation is predominantly a biological soil crust consisting of different types of lichen-rich communities, one of the more conspicuous being dominated by Diploschistes diacapsis (Ach.) Lumbsch. This lichen is mainly restricted to the north- facing slopes, where it forms extensive whitish carpets and probably plays an important role in preventing erosion of the slopes and allowing plant colonization. South-facing slopes are much more eroded and generally lack vegetation. %The photosynthetic performance of north (shade) and south-facing (sun) populations of D. diacapsis was studied to determine if these different populations showed any adaptations to the microclimatic conditions of their individual habitats. The response of CO2 exchange to light intensity, temperature and water content was measured under controlled conditions in the laboratory. Dry weight-based net photosynthetic rates were higher in the southern-exposed population but quantum efficiency, and light compensation points were similar. Thallus weight per unit area (LMA) was considerably higher for shade specimens but maximum water content and optimal water content were very similar and chlorophyll content on a dry weight basis was also similar. Chlorophyll content on an area basis was higher in the northern-exposed population and always much larger than those reported in other studies on the same species (up to 8 times larger) with the result that NP values on a chlorophyll basis were relatively low. The larger LMA meant that shade thalli stored more water per unit area which should ensure longer active periods than sun thalli. The results support a strategy pair of high NP and short active time versus low NP and long active time, both having been reported for other soil crust species. However, the visibly larger biomass of the shade D. diacapsis suggests that the lichen is at the limit of its adaptability in these habitats.

Two species of Halecania from Asia, H. lobulata van den Boom & Elix and H. pakistanica van den Boom & Elix are described as new to science. In addition, the new combination Halecania pepegospora (H. Magn.) van den Boom is made. The ecology, distribution and chemistry of some selected species are discussed and a key to the fifteen species known worldwide is given.

A new species of Cryptothecia (Arthoniales, lichenized ascomycetes) is described from Northern Thailand. The species has been collected from planted mango trees at a single site in a rural area and is characterized by the punctiform soralia, soredia containing gyrophoric acid and 8-spored asci.

Diurnal courses of photosystem II (PS II) activity of Xanthoria elegans were continuously monitored using a novel technique of chlorophyll fluorescence imaging in the field (maritime Antarctica) over a period of 7 days. The lichen specimens grew on rock surfaces in a north-facing coastal area of Galindez Island (Argentine Islands). A portable fluorometer FluorCam equipped with a CCD camera and image analysis software was placed over a thallus so that false colour images of FV/FM and quantum yield of photochemical processes in PS II (ΦII) distribution over the thallus could be taken over the course of a day. Simultaneously, microclimatic parameters of the habitat were recorded: air and thallus temperatures, relative air humidity, PPFR (photosynthetic photon fluence rate) and global radiation. Photosynthetic processes in X. elegans were activated by rainfall or water from melting snow. After thallus hydration, FV/FM and ΦII gradually decreased from their maximum values due to evaporation and progressive loss of water from the thallus. Chlorophyll fluorescence imaging showed that the thallus dehydration started from the margins and moved towards the central thicker thallus zones. These zones exhibited higher activity of PS II than the margins throughout the day. The rate of inhibition of photosynthetic processes in PS II was faster at the margins than in the centre of the thallus. Dependence of ΦII on thallus water potential (WP) was investigated during gradual dehydration under laboratory conditions. After a decrease in WP from zero to −7 MPa, X. elegans exhibited only a 13·8% decrease in ΦII from its maximal value. Within the range of WP of from −8 to −20 MPa, the ΦII decrease was more rapid reaching the critical point (ΦII=0) at WP of approximately −25 MPa. Chlorophyll fluorescence imaging and WP measurements showed that X. elegans is capable of maintaining detectable photosynthetic activity even at extremely low WP. Based on our microclimatological data, X. elegans may be photosynthetically active under field conditions for several hours after being wetted by rain or snowfall. It is suggested that chlorophyll fluorescence imaging is a powerful technique, transferable to field conditions and capable of visualizing heterogeneity of photosyntetic processes over a lichen thallus subjected to periodic dehydration.

The distributions of natural stable isotopes of carbon and nitrogen have been extensively investigated in a variety of primary producers such as vascular plants and algae to provide baseline information of the trophic structure of various ecosystems (Currin et al. 1995). However, there have been few attempts to use this ecological approach to characterize lichens which frequently constitute the principal vegetation in many rocky habitats (Gilbert 2000). Rocky sea shores are characterized by a vertical zonation of biological communities which fall into three major zones: supralittoral, mediolittoral and infralittoral. The supralittoral zone is rarely submerged and is typically covered by a vegetation of lichens and cyanobacteria (Lewis 1964; Russel 1991).

Lepraria aurescens and Lepraria pulchra are described as new from bark in Thailand; both contain thamnolic acid, but differ in thallus form and colour.