The anatomy of the endolithic, calcicolous lichen Verrucaria rubrocincta Breuss is described using optical and scanning electron microscopy. This lichen is locally abundant in caliche plates of open desert pavements in the Sonoran Desert of south-western Arizona. The endolithic growth of V. rubrocincta is distinctly layered. The upper layer is a fine-grained calcite (micrite). This layer is sparsely penetrated by hyphae and therefore cannot be interpreted as a lithocortex sensu stricto. Beneath the micrite is the photobiont layer. Below this photobiont layer hyphae form a pseudomedulla penetrating up to 1 cm into the caliche. Calcium oxalates occur in the pseudomedulla but are absent from uninhabited caliche. The analogy of a greenhouse describes the ecophysiological adaptations of this endolithic growth to the environmental extremes of the Sonoran Desert. The micrite acts as a roof and the photobiont layer and pseudomedulla represent the greenhouse interior. Verrucaria rubrocincta has thus evolved a strategy to successfully establish and survive within an extreme environment. Our study illustrates biodeterioration and biomineralization processes acting simultaneously within a single lichen species. Mineralogical evidence suggests that the micrite on the thallus surface is biologically induced. The hyphae of the lichen biodeteriorate the caliche thus forming the pseudomedulla. Simultaneously with this process micrite forms at the surface protecting the thallus from exposure and counter-balancing rock degradation. These combined effects of biodeterioration and biomineralization do not markedly accelerate erosion because inhabited and uninhabited areas of the same plate show similar surface heights.

Cellular responses to copper stress were investigated for the first time in a saxicolous lichen species, Lecanora polytropa (Hoffm.) Rabenh. Bright blue-green apothecia accumulated up to 1·3% Cu on a dry weight basis (205 μ mol Cu g−1), c. 50% in an exchangeable form. A bright turquoise-blue layer extended beneath the hymenium into the medulla, above and between a dentate photobiont layer. Oxalic (1·88 μ mol g−1), citric (0·83 μ mol g−1) and lower concentrations of malic (0·45 μ mol g−1) acids were determined by GC/MS analysis. Short-term exposure to high Cu2+ concentrations (40 and 400 μ mol g−1) under non-complexing conditions caused a dose-dependent decrease in chlorophyll a content; chlorophyll b and total carotenoid contents remained constant. The phaeophytinization quotient remained unchanged during Cu2+ exposure. Analysis of thiol peptides confirmed glutathione was reduced (GSH) in native L. polytropa (0·538 μ mol g−1), and phytochelatins (PC2 and PC3) oxidised. Short-term exposure to 40 μ mol g−1 Cu2+ oxidised c. 28% of the glutathione pool; oxidised phytochelatin concentrations remained unchanged. This is the first report of phytochelatin production and thiol peptide status in a crustose lichen. These represent two possible detoxification mechanisms in this Cu-tolerant species. Copper complexation by low molecular mass organic acids and non-protein thiols do not entirely account for its tolerance.

This study aims to investigate patterns of species richness and abundance in relation to stand age in 71 Picea abies plantations, aged between 9 and 85 years, situated in the oceanic region of Central Norway. The study has shown that plantations within the oceanic spruce forests can support a relatively high number of epiphytic lichen species. Some of the oldest plantations hosted several old-forest associated species, e.g. Hypogymnia vittata, Lobaria pulmonaria, Pseudocyphellaria crocata and Ramalina thrausta. The number of species was influenced significantly by stand age and increased rapidly in stands <20 years old. Stands >30 years old showed no clear increase in species number, except for a high number of species in the two oldest stands. The colonization pattern could be characterized as an additional entrance of species, rather than by a replacement sequence. The probability of occurrence increased steeply at young stand ages (<20 years) for Bryoria spp., Cavernularia hultenii, Platismatia glauca, Parmelia sulcata and Usnea spp. A lower rate of colonization was characteristic for Alectoria sarmentosa, Parmelia saxatilis and Platismatia norvegica. The cover of foliose lichens on the branches showed an almost unimodal response to stand age. The cover of lichens was highest on branches in middle-aged plantations. The reason for the lower lichen cover in late successional stages, compared to middle-aged stands, could be due to reduced light in the lower canopy of mature plantations. Increased rotation cycle, creation of gaps and short distance to sources of propagules are factors suggested to promote species richness and abundance in forest plantations.

The aim of this investigation was to determine the NH4Cl concentration threshold, above which negative physiological effects would occur in the nitrophytic lichen Xanthoria parietina. Over a 10 month period, X. parietina thalli growing on roof tiles were exposed weekly to NH4Cl concentrations of 0·04, 0·17, 0·34 or 0·69 M. Nitrogen (N) uptake from ammonium and the concentrations of total thallus N and biont markers (chlorophyll a, ergosterol and chitin) were measured on four occasions, over the experimental period. Xanthoria parietina was able to assimilate a significant quantity of the applied ammonium. However, lichens exposed to the two higher concentrations suffered damage to both the photobiont and the mycobiont, as evidenced by reduced chlorophyll a and ergosterol concentrations, while lichens exposed to the two lower concentrations showed no significant changes in either chlorophyll a or ergosterol that could be related to the ammonium inputs. Xanthoria parietina tolerated a weekly irrigation of at least 0·17 M NH4Cl, corresponding to an N deposition of c. 1000 kg ha−1 yr−1, suggesting that this species has a very high tolerance to N pollution.

Takhtajan's floristic regions of the world, based on vascular plant distribution, were used for a comparative analysis of foliicolous lichen biogeography. Of the 35 regions distinguished by that author, 23 feature foliicolous lichens. The South-East African, Fijian, Polynesian and Hawaiian regions lack sufficient information and were excluded from further analysis. Using multi-dimensional scaling and cluster and cladistic analyses, the remaining 19 regions were grouped into six lichenogeographical regions: (1) Neotropics, (2) African Paleotropics (including Madagascar, Réunion and Seychelles), (3) Eastern Paleotropics (including North-East Australia and New Caledonia), (4) Valdivian region (temperate rainforest in southern South America), (5) Tethyan region (subtropical areas of Macaronesia, Mediterranean, and Western Irano-Turanian) and (6) Neozealandic-Tasmanian region (temperate rainforests of New Zealand and Tasmania). Affinities between these six large scale regions, with 57–77% shared species, are still stronger than those between the 35 smaller scale regions denned by Takhtajan [(20−)40–60(−75)% shared species]. Based on presence/absence within each of the six regions, 22 potential distribution patterns were defined for foliicolous lichens. Many species are widely distributed; 21% are cosmopolitan or pantropical, while 19% are disjunct on at least two continents, and only 60% are restricted to one of the three major tropical areas (nearly 100% in vascular plants). Most of the latter are found in the Neotropics, while the African Paleotropics are poor in endemics. Most genera deviate significantly from overall distribution patterns; for example, Strigula and Calopadia have higher proportions of widely distributed species, while Porina displays a concentration of Eastern Paleotropical endemics. Species diversity and composition of the six regions indicate that the three extra-tropical foliicolous lichen biotas (Valdivian, Tethyan, Neozealandic-Tasmanian) are the result of partly separate evolutionary histories. On the other hand, there is a strong affinity between the Neotropics and the African Paleotropics, suggesting a shared Western Gondwanan element in the foliicolous lichen biotas of these two regions.

Surveys of the distribution of the lichens Xanthoria panetina and Ramalina duriaei in Israel showed that environments with air pollution had no damaging effectson X. panetina, whereas R. duriaei had disappeared from polluted environments: physiological studies supported this relative sensitivity. Investigations of possible defence mechanisms protecting X. parietina from the damaging effects of air pollution showed a multitude of possible protective systems. These included constitutive avoidance such as: efficient buffering capacity; a relatively high potassium content; and antioxidation by parietin, and induced tolerance such as: SO2 oxidation to non-toxic sulphate; increased glutathione content; induced praline and arginine synthesis; and increased detoxification of active oxygen forms.

The species-level taxonomy of the genus Graphis sensu Staiger was revised using numerical taxonomy and cladistic techniques. In its current circumscription, Graphis includes more than 300 species and is characterized by lirellae with well-developed, carbonized labia usually concealing the disc and usually hyaline, I+ blue-violet, transversely septate to muriform ascospores. The study analyzed the importance of morphological, anatomical, and chemical characters for taxonomic purposes in the genus, both at species level and at the level of species groups and lineages. A phenotype-based cladistic analysis, combined with a novel method to estimate the degree of character state homoplasies prior to a cladogram, as well as a species ordination using non-metric multidimensional scaling (NMS), was performed to assess the delimitation of potentially natural groups within the genus. Contrary to previous views, the most important character complex characterizing potentially natural groups in the genus Graphis is lirellae morphology, whereas labia striation, excipulum carbonization, ascospore features, and secondary chemistry, vary greatly even in closely related species. Based on these findings, Wirth and Hale's concept of ‘sporomorphs’ is emended to generally characterize morphologically similar species that differ in a single character, such as labia striation (‘labiomorph’), excipulum carbonization (‘excipulomorph’), hymenium inspersion (‘inspersomorph’), ascospore size and septation (‘sporomorph’) and secondary chemistry (‘chemomorph’).

Lichen growth is reviewed in the context of the anatomy of the growth region, thallus morphology of crustose and foliose lichens, photosynthesis, mathematical models and their application. The Aplin & Hill model is suggested as a basis for more detailed investigation of integrated processes of growth including not only the size increase but also the general structure of the thallus and the processes which limit growth.

The distribution of sixty-six Peltigera species in 230 biogeographic provinces or 40 regions are presented. A hierarchical clustering approach, used to identify clusters of species with similar distribution patterns (floristic elements), resolved four groups made up of Neotropical, Southern Hemisphere, Antarctic and mainly Holarctic species. The Holarctic Kingdom is species rich with the highest number of Peltigera species and also the highest number of endemic species; the Australian and Cape Kingdoms have the lowest number of species and endemics. The species rich provinces are briefly discussed.

The phylogenetic relationships of the genus Bryoria were examined using ITS, partial glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and mitochondrial SSU rDNA sequence data in addition to 20 chemical and morphological characters. This first comprehensive molecular study to assess Bryoria phylogeny includes representatives from all the traditionally recognized four sections. Combined cladistic analyses of 88 Bryoria specimens representing at least 25 species resulted in highly resolved phylogenies. Based on the results, a new infrageneric classification for the genus is proposed. Five sections are recognized, largely corresponding to the existing classification, with the addition of section Americanae. The study shows that while most species with an erect growth-form are clearly monophyletic, current species status of many pendent taxa can be questioned.

Algal genotypes should freely associate with different lichen fungi that grow in the same confined habitat giving the appearance of low levels of selectivity and specificity. If genetic compatibility between algal and fungal partners limits the combination of partners, then some degree of taxonomic specificity should be evident. This study examined the photobiont composition in a community of epiphytic lichens on Jack Pine to investigate selectivity and specificity. The objectives of the study were to infer algal identity, to infer photobiont dispersal, and to investigate the distribution of algal genotypes relative to the fungal partner. Photobiont variability was determined by Restriction Fragment Length Polymorphism (RFLP) and nucleotide sequences of the Internal Transcribed Spacer (ITS) of ribosomal DNA (rDNA). Seven species of lichen-forming fungi are reported to associate with five divergent algal genotypes, with only one species, Evernia mesomorpha, showing some degree of selectivity and specificity. The algae represent at least two species (Trebouxia jamesii and T. impressa) for the area confined to 200cm2 on the north side of 20 Jack Pine trees. Gene flow was inferred in this tightly defined community of lichenized algae. The algal sharing and inferred gene flow may suggest that soredia provide a means of algal transport and distribution among lichen-forming fungi in the habitat.

A portable system for CO2 gas exchange measurements is described which allows determination of photosynthesis and respiration rates of lichens (and mosses) in the field under light, humidity and temperature conditions which are close to ambient. Time periods for enclosure of the thalli in a cuvette of this CO2-porometer for gas exchange measurement are shortened to between 1 and 2 min, so that an experimental influence on their water relations is small. Between the periods of gas exchange measurement, the lichens experience their natural microclimate conditions. Thus, measurements approximate closely the true gas exchange rates of the lichens under natural conditions. Diurnal courses of CO2 exchange of lichens found growing in a Mediterranean habitat in the spring are demonstrated, as determined by this method.

Diel (24-h) time courses of microclimate, water relations, and CO2 exchange were measured under quasi-natural conditions at a forest edge in a lower montane, tropical rainforest in Panama for six Lobariaceae (Lobaria crenulata, L. dissecta, Pseudocyphellaria aurata, P. intricata, Sticta sublimbata, S. weigelii). Responses to experimentally controlled water content (WC), photosynthetic photon fluence rate (PPFR), and temperature were studied in most detail with P. aurata.

Photosynthesis was well adapted to high temperatures, and all species exhibited ‘shade plant’ characteristics with low light compensation points and low light saturation. Lobaria and Pseudocyphellaria species suffered from a strong depression of net photosynthesis (NP) at suprasaturating WC; suprasaturation depression was less in cyphellate Sticta species.

Photosynthetic capacity correlated with thallus nitrogen concentration, and maximal NP rates of the cyanobacterial Sticta species was 4 to 5 times higher than that of the green algal Lobaria species. However, high rates of NP were uncommon and brief events under natural conditions; the different environmental factors were rarely optimal simultaneously. Similar to earlier observations with other rainforest lichens, NP ceased during the period of highest irradiation on most days due to desiccation. During moist periods low light often limited carbon fixation, and high thallus hydration was often detrimental to NP. In spite of these limitations the maximal daily integrated net photosynthetic carbon income (ΣNP) was quite high especially for the Sticta species [17·3 and 24·1 mgC (gC)−1 day−1 for S. sublimbata and S. weigelii, respectively]. High nocturnal carbon loss, due to high night temperatures and continuous hydration, resulted in frequent negative diel carbon balances (ΣC) in all species. The average nocturnal carbon loss amounted to 83 and 70% ΣNP for P. aurata and P. intricata, respectively and to 64 and 59% of ΣNP for S. sublimbata and S. weigelii, respectively. Their average diel ΣC was as high as 3·7 and 5·3 mgC (gC)−1 day−1. In contrast, ΣC was much lower for the other species, it amounted to only 0·18 mgC (gC)−1 day−1 for L. crenulata. Thus, the Sticta species stood out amongst the species studied for their most successful adaptation of photosynthetic productivity to the habitat conditions in the lower montane rainforest.

This article traces the changing systems in the classification of the parmelioid lichens from the early 19th century to the present day. Molecular phylogenetic approaches have enabled the relative importance of traditionally used characters to be objectively re-assessed, and led to the realization of the significance of others that had previously been passed over or dismissed; for example, differences in ascospore and conidium types or the cell-wall constituents. Information on the different characters employed is presented and assessed. It is concluded that characters related to thallus form or chemical products prove to be less informative at the generic level than has sometimes been assumed. Features requiring further study are identified, and in the light of experience in this group, lichenologists should be cautious in translating their results into formal taxonomies.

The fruticose lichen Cavernularia hultenii exhibits a strongly disjunct distribution between north-western North America, Newfoundland and north-western Europe. An investigation of its population structure, based on nuclear ITS and IGS DNA sequences, shows that western North America has a higher number of haplotypes than the two other areas. Most of the haplotypes confined to this region are rare and occur outside the area that was affected by Pleistocene glaciations. Three haplotypes are common in all three areas. The high number of haplotypes in western North America might be due to a combination of events during the Pleistocene and Holocene epochs, viz. increased lineage survival by repeated fragmentation of populations and reduced lineage extinction through rapid postglacial expansion and population growth.

The phycobionts of 20 different lichens were studied in culture, described and assigned to species of Pseudotrebouxia and Trebouxia. Identical phycobiont species were isolated from widely different lichens which showed that these algal symbionts were not specific to particular mycobionts. There was much variation in cellular detail within individual algal species indicating that the criteria currently used to separate species of these phycobionts may be too restrictive.

An artificial key for the identification of 218 lichen-forming, parasitic, parasymbiotic and saprophytic fungi reported as occurring on lichens in the British Isles is provided. Agyrium flavescens Rehm, Cyphelium marcianum B. de Lesd., Scutula krempelhuberi Körber and Stigmidium solorinaria (Vainio) comb. nov. are reported from the British Isles for the first time, and three further new combinations are made: Bacidia killiasii (Hepp) comb, nov., Pleospilis ascaridiella (Nyl.) comb. nov. and Polycoccum gelidaria (Mudd) comb. nov. References to publications in which further information on the species can be found are included. Illustrations of the spores of 141 species and an index to the names of fungi and hosts are also presented.

Bryoria fremontii and B. tortuosa are the only species in the lichenized ascomycete genus Bryoria known to contain the pulvinic acid derivative vulpinic acid. In B. fremontii this yellow pigment is restricted to the soralia and apothecia, while in B. tortuosa it can occur throughout the thallus. The actual amount of vulpinic acid produced by B. tortuosa is rather variable, however, with intermediate specimens bearing both white and yellow pseudocyphellae. We studied the relationship between the two species with parsimony analysis using four DNA regions: 1) the internal transcribed spacers of the nuclear rDNA including the 5.8S region (ITS), 2) partial sequences from the intergenic spacer of the nuclear rDNA (IGS), 3) partial sequences from the small subunit of the mitochondrial rDNA (mtSSU), and 4) partial sequences from the protein-coding glyceraldehyde-3-phosphate dehydrogenase gene (GAPDH). Our phylogenetic analysis revealed that B. fremontii and B. tortuosa must be regarded as conspecific, but allowing for some genetic differentiation between European and North American populations. Bryoria tortuosa is therefore synonymized with B. fremontii.

The past and present occurrence of Usnea longissima has been investigated at 31 localities in an area of eastern central Sweden. A marked decline was found which is due to different forestry practices, and, to a minor extent, air pollution. The species is confined to old spruce forests, mainly located on north-facing slopes with a slightly oceanic climate. The population size showed a large variation both within and between seven investigated localities. Specific habitat demands and low dispersal ability make U. longissima very sensitive to environmental disturbances.

Fourteen genera belong to a monophyletic core of cetrarioid lichens, Ahtiana, Allocetraria, Arctocetraria, Cetraria, Cetrariella, Cetreliopsis, Flavocetraria, Kaernefeltia, Masonhalea, Nephromopsis, Tuckermanella, Tuckermannopsis, Usnocetraria and Vulpicida. A total of 71 samples representing 65 species (of 90 worldwide) and all type species of the genera are included in phylogentic analyses based on a complete ITS matrix and incomplete sets of group I intron, β-tubulin, GAPDH and mtSSU sequences. Eleven of the species included in the study are analysed phylogenetically for the first time, and of the 178 sequences, 67 are newly constructed. Two phylogenetic trees, one based solely on the complete ITS-matrix and a second based on total information, are similar, but not entirely identical. About half of the species are gathered in a strongly supported clade composed of the genera Allocetraria, Cetraria s. str., Cetrariella and Vulpicida. Arctocetraria, Cetreliopsis, Kaernefeltia and Tuckermanella are monophyletic genera, whereas Cetraria, Flavocetraria and Tuckermannopsis are polyphyletic. The taxonomy in current use is compared with the phylogenetic results, and future, probable or potential adjustments to the phylogeny are discussed. The single non-DNA character with a strong correlation to phylogeny based on DNA-sequences is conidial shape. The secondary chemistry of the poorly known species Cetraria annae is analyzed for the first time; the cortex contains usnic acid and atranorin, whereas isonephrosterinic, nephrosterinic, lichesterinic, protolichesterinic and squamatic acids occur in the medulla. Notes on the anatomy of Cetraria annae and Flavocetraria minuscula are also provided.