The effects of simulated sulphuric acid rain were investigated, under controlled laboratory conditions, on the surface structure and n-alkane composition of the lichen Pseudevernia furfuracea. Thalli were collected from Larix decidua bark in a wood in a Piedmont alpine valley and treated with three concentrations of H2SO4. The response to simulated acid rain was a clear change in the quantitative alkane composition, with a decreasing trend observed for C28 and C30 with increasing sulphuric acid concentration. From a morphological point of view, a progressive reduction of the surface amorphous layer was observed as a consequence of the exposure of thalli to the acid rain treatments.

The lichen vegetation of forty-five acid watercourses in England is described and related to ecological variables. The zonation scheme adopted for chalk and limestone streams that involves four overlapping bands of lichen vegetation related to length of submergence is also appropriate for this habitat. The flora involves around 90 species, a number of which are rarely recorded specialists. Evidence is presented that substratum chemistry is a more powerful ecological factor than water chemistry. An attempt has been made to relate the lichen flora to homogeneous stream segments from the headwaters down to the alluvial lowlands. An investigation into the effects of water quality showed that both suspended solids (silting) and eutrophication are highly deleterious to the lichen flora; the submerged and fluvial mesic zones are the first to be affected. The zonation across streams in England is compared with those reported from Germany and found to be closely similar.

Flavobathelium epiphyllum gen. et sp. nov. is described and illustrated. The new taxon is characterized by perithecia and pyenidia embedded in pulverulaceous, uni- to plurilocular pseudostromata, small, transversely septate ascospores, and the presence of bacillar to filiform macroconidia with gelatinous appendages and simple microconidia. Possible relationships are seen with the genus Phyllobathclium. Flavobathelium epiphyllum is a common species in Central and South American lowland to submontane rain forests with undisturbed vegetation. It is mostly found along moderately illuminated parts of the understory, such as small, natural light gaps.

Intraspecific thallus interactions in mixed populations of Rhizocarpon lecanorinum and R. geographicum in North Wales are described. In contrast to the most commonly occurring morphotype of R. geographicum, which forms mosaics comprised of sharply delimited individual thalli, R. lecanorinum thalli consistently merge with one another at intraspecific contacts, leaving no visible trace of their initial boundaries. On the analogy of mycelial interactions in populations of wood-rotting and other non-lichen-forming fungi, it is postulated that these differences are the outcome, in R. geographicum, of somatic incompatibility between distinct genotypes, and in R. lecanorinum of somatic compatibility among genetically identical or very closely related thalli. Possible mechanisms for the evolution of clonal population structure in R. lecanorinum and links between somatic interactions and reproductive output in these species are discussed. Facultative parasitism of R. lecanorinum by Schaereria fuscocinerea, and resistance to such parasitism by cooccurring R. geographicum, are also documented.

Ramalina panizzei De Not. is reported from Switzerland and north of the Alps for the first time. Recent collections and thalli found amongst specimens of R. fastigiata (Pers.) Ach. are described; the species is obviously not restricted to the Mediterranean. The confusion in several herbaria around this and related corticolous species, particularly R. subgeniculata Nyl. and R. fastigiata, can be traced back to imprecise original and subsequent diagnoses, all of which lack a clear species delimitation. Similarities and differences of these species are discussed. In addition, sequences from the rDNA ITS regions were determined for two individuals of R. panizzei and two of R. fastigiata, including one of each from a site where both species grow intermixed. Kimura 2-parameter genetic-distance estimates indicate that R. panizzei and R. fastigiata are as different from each other as either is from the reference species R. siliquosa (Hudson) A. L. Sm. s.l. A broad-based taxonomic revision of involved species is not possible due to the limited number of analyses, but the results demonstrate the potential for using DNA sequence data to investigate species-level questions in lichens. Based on morphology, chemistry, and DNA sequence data, R. panizzei is retained as a distinct species.

Cladina subtenuis establishes and expands by mechanisms of the thallus mycobiont. Vegetative reproduction occurs through thallus fragmentation, branch ‘ de-differentiation ’, and the extension of the underground prothallus. Establishment hyphae can be considered as any hyphae that provide the mechanism for these modes of clonal thallus extension. They may originate in various parts of the thallus, laterally on branch surfaces, at the growing tips of branches, or from the inner fungal layers of the podetium. The thallus of C. subtenuis is structurally and functionally plastic. Parts of the photosynthetic lichen thallus can transform into nonphotosynthetic fungal aggregations, and non-photosynthetic aggregations may re-establish as a photosynthetic lichen thallus. These activities expand the area occupied by the clone, and potentially increase its photosynthetic surface.

Porina howeana sp. nov., P. Mariae sp. nov. and P. ocellatoides sp. nov. are described from shaded basalt on Lord Howe Island, New South Wales, Australia.

Field emission scanning electron microscopy was used to characterize mycobiont wall surfaces in Umbilicaria hyperborean from Greenland. To determine the precise intrathalline distribution of phenolics, comparisons were made of hyphal surface features and dimensions before and after acetone extraction. Stratification was evident within the medulla, as extracellular phenolics were observed only on hyphae near or within the algal zone. The outside diameter of hyphae in this region was thus significantly greater than in the remainder of the medulla. Surface deposits were also examined in 1350-year-old subfossil thalli and hyphal diameters were compared statistically to those in extant thalli. The mean hyphal diameter in the upper medulla was not significantly less in subfossil specimens than in recent thalli, suggesting that phenolic cover was maintained in spite of glaciation. However, after ice burial phenolic masses tended to be flatter than in recent specimens and finely tubcrculate. The appearance of mycobiont hyphae in the cortex of subfossil thalli seemed to be the same as in extant thalli, except that there tended to be more compressible, smaller and less conglutinated filaments near the algal layer.

The genus Australiaena (lichenized Ascomycetes, Physciaceae) with the single species A. streimannii sp. nov. is described as new from tropical Australasia. Morphologically it is characterized by crustose thalli with an often radiate-plicate margin, ascospores with a type-B ontogeny, and filiform spermatia. The chemistry of this taxon is diverse (lobaric acid, conlobaric acid, xanthones, gyrophoric acid, lecanoric acid, 5-O- ethylhiascic acid, perlatolic acid), and three chemotypes are distinguished.

Comparisons of whole-lichen physiology to the respective photobionts have often been unclear due to inherent differences in isolated photobiont culturing techniques. The use of 13-mm-diameter cellulose-acetate discs allows photobiont cultures access to nutrient agar medium, while improving ease of manipulation and distinct separation from the agar. Adequate culture growth for experimentation is reached in approximately three weeks, a time comparable to standard nutrient agar and liquid cultures. These discs are then available for use in a variety of manipulative techniques. Chlorophyll determination of an entire algal disc culture is obtainable because the discs readily dissolve in dimethylsulphoxide (DMSO), with no interference in the 400–700 nm range. Photosynthesis and respiration may be measured with standard gas exchange equipment. Photobiont discs allow for fumigation in the gas phase with no increase in external ⊂pH reported to occur during gaseous fumigations in liquid media. The disc system is also useful for fluorescence studies. Trebouxia erici cultures exhibited a CO⊂2 gas exchange on a gram dry weight basis similar to whole lichen systems. The ease with which photobionts can be cultured and manipulated using this system allows for expanded experimentation and comparisons.

The pustules on the surface of the umbilicate lichen Lasallia pustulata are moved away from the centre and towards the thallus margins with an average speed of 1.8 mm per year, revealing a growth pattern organized radially and flowing from the centre of the thallus. Pustules close to the margin move substantially faster than those close to the centre; for each 10 mm added to the initial distance from the centre, the speed of outward movement is about doubled. This suggests that intercalary growth over the entire thallus is displaced outwards in an accumulating manner, accelerating the pustules. Moving away from the centre the pustules expand, often collapse in the middle, and mature by developing isidia. In the less active (senescent ?) margins the pustules are eroded away and the supplementary intercalary growth seems insufficient to keep the outflowing thallus intact. Thus the margins are disrupted into irregular lobes.

Usnea longissima was sampled in SE Norway on six main branches of one Picea abies, comprising its full vertical canopy range. Nearly all specimens (n = 781) were unattached and fragmented, in contrast with associated lichens. A combination of weak axes and lack of holdfasts resulted in a population of repeatedly displaced thalli, a similar situation as in ground-dwelling vagant lichens. Comparisons with a litterfall population indicated that thalli, regardless of size, had a similar probability to end as litter on the ground. Specimens were frequently sorediate, but only 12 small thalli with a basal holdfast had been directly recruited through soredial establishment. Its patchy distribution within apparently homogenous forest stands is probably a consequence of a rare successful long-range dispersal through soredia coupled with an abundant local dispersal of coarse thallus fragments. Old forests with ample, diffuse skylight at lower and humid canopy levels are probably essential to maintain a vagant epiphytic life form with a predominantly downward dispersal of thallus fragments.

The new genus Vagnia is introduced for the single species V. cirriformia discovered on thalli of Peltigera in Poland; it appears to be a pathogen as the cortex is destroyed in a rounded patch within which the conidiomata occur. The fungus is characterized by cupulate to doliiform conidiomata clothed in white hairs and from which a black columnar cirrus of conidia arises. The simple ellipsoid conidia are hyaline when viewed individually and are formed enteroblastically from elongate conidiogenous cells supported by branched conidiophores.

To identify representative quantitative criteria for the creation of a future Red List of epiphytic lichens, 849 trees in 132 long-term ecological observation plots in the Swiss Central Plateau and the Pre-Alps were surveyed by standard sampling. Based on the trees, frequency data of the lichen taxa observed are described by the log series model, indicating the controlling effect of few ecological factors. Based on the plots, four classes of scarcity, each comprising 25% of the species, were established. As a contribution to the development of a national, representative survey of lichens, α-diversity (species richness, species density) and β-diversity (dissimilarity) were calculated in terms of region, vegetation formation, vegetation belt and for their combinations. Differences in lichen diversity between the Central Plateau and the Pre-Alps were caused by the bigger elevational range in the Pre-Alps, which resulted in a higher species richness. α-Diversity of forest and non-forest were similar, whereas each vegetation formation showed one third of its species restricted to it. The contributions to the total lichen diversity of crustose, foliose and fruticose as well as of generative and vegetative species was calculated. Specific features along the altitudinal gradient of vegetation belts emerged: the percentage of crustose and generative lichens declined with every altitudinal step, increased in fruticose and vegetative lichens, and was the same in foliose species.

A molecular study was undertaken to clarify the identity of the photobiont in colourmorphs of the lichen, Peltigera membranacea. Two strains of cyanobacteria, identified as Nosroc sp. by morphology, were cultivated from each of two lichen specimens. Prokaryotic (16S) ribosomal RNA gene fragments were amplified by the polymerase chain reaction (PCR) from DNA extracted from the isolated strains and the lichens, and sequenced directly. Sequences were 98 1% identical between lichen specimens, TDI#AR94 and TDI#AR95, and highly similar to sequences published, or generated in this study from a type culture, for Nostoc. The 16S ribosomal RNA gene sequences (‘ 16S rDNA’) of all four lichen-derived cyanobacteria appeared the same, even though the lichen specimens from which they originated had different sequences. The 16S rDXA from strains 9A and 9B were different from that of specimen TDI#AR94, the thallus from which they were isolated, and instead were the same as that of strains 10A and 10B, and their source, specimen TDI#AR95. When primers selective for the strain 9A sequence were used, however, a small amount of PCR product corresponding to the 16S rDNA of strain 9A was obtained from lichen TDI#AR94. The results confirm that the photobionts of P. membranacea belong to Nostoc, and suggest that genetic differences in the photobiont may be a factor in the occurrence of colourmorphs among cyanolichens.

Field measurements of CO2 exchange by lichens are difficult because these poikilohydric organisms rely on direct hydration by rain, dew or fog. Continuous enclosure of thalli in conditioned, measurement cuvettes is, therefore, not experimentally reasonable. Porometric instruments with brief enclosure times, have proved useful for studies of lichen gas exchange but allow only spot measurements and recording is not easily possible for extended time periods. We describe a newly developed, automatically operating cuvette that allows long-term monitoring of lichen photosynthetic and respiratory CO2 exchange in the field. Samples, e.g. flat stone slabs covered with epilithic lichens, are positioned on the base of the cuvette where, when the cuvette is open, they are exposed to the same environmental conditions as naturally growing thalli. At regular intervals (typically 30 min), an upper lid automatically encloses the lichen for c. 3 min in a stirred cuvette; CO2 exchange is measured using IRGA techniques and microclimate data arc recorded. The successful operation of the cuvette is illustrated by means of diel time courses of CO2 exchange for selected, very different weather conditions.