The new genus Bulbothricella (Lichenized Ascomycotina,Parmeliaceae with the single species B. amazonensis (Marcano, Galiz & Morales) Marcano, Galiz, Morales & Mohali is segregated from Bulbothrix. This conclusion is based on an investigation of morphological, anatomical and chemical characters using scanning electron microscopy and thin-layer chromatography. The new genus is characterized by a pored epicortex, 12—14 spores per ascus, obovate and acrogenous conidia, and an anatomical structure and cortical chemistry resembling that of Bulbothrix..

The lichen vegetation associated with calcareous rocks, areas of long snow-lie and the margins of high-level lakes in North Wales is described. It includes Porpidia ochrolemma (Vain.) Brodo & R. Sant. and Rhizocarpon anaperum (Vain.) Vain, new to the British Isles, plus a further 30 taxa recorded for the first time from Wales. The relative importance of the montane lichen vegetation of North Wales is assessed by comparison with areas in other parts of the British Isles. It is shown to exceed in interest any montane area in England or Ireland but to be below the standard of an otherwise comparable area in Scotland.

The genus Lecidea in the lichen flora of the gypsum soils of Spainis represented b two species: L. gypsicola Llimona and L. circinarioides Casares & Hafellner sp. nov., which are described in this article. Chemical, anatomical and ecological differences are also described, as is the taxonomic value of the morphological characteristics of the mature ascoma.

The distribution and succession of epiphytic and other associated lichens on blackthorn (Prunus spinosa) growing on the shingle at Dungeness is described. Some 33 epiphytic species, which exhibited a range of ecological strategies from pioneer to late colonizers, were recorded. Both the rate of change of status (age) of blackthorns and the progress of lichen colonization seemed to depend on whether the bushes were growing directly on shingle or on adjacent alluvial soil; both processes seeming to be more rapid on the former substratum. Terricolous lichens, of which 18 were recorded, generally appeared late in the succession and mostly amongst bushes growing on shingle. Rabbits often invaded the blackthorns, especially those on alluvium, and probably contributed to the lack of terrestrial lichens under these bushes. Blackthorns growing on shingle tended to be more prostrate in form than those on alluvium.

For experiments run at 350 ppm CO2, the subtropical lichen Coenogonium does not exhibit net photosynthetic depression at water contents above those at which initial maximal values are reached. This is in contrast to most lichens for which such a depression occurs. We infer that the results reflect the unusual morphology of Coenogomum, in which the alga is the dominant symbiont, occurring as filaments at the lichen surface. This arrangement should minimize CO2 diffusion resistance to the algal surface. With light saturation occurring by 70 μmol photons m−2 s−1, Coenogoniium has one of the lowest light saturation values reported among lichens.

The results of a nationwide survey of lichens associated with streams on chalk and limestone are reported. The lichen communities are present as a series of overlapping bands related to length of submergence. These have been named the submerged, fluvial mesic, fluvial xeric and fluvial terrestrial zones. The flora involves around 50 lichens, many of which are rarely recorded specialists restricted to this habitat. The richest sites for submerged species are headwaters, especially around springs. Active tufa deposition and disturbance of the stream bed by farm stock are detrimental to aquatic lichens. Diversity further downstream is related to the amount of exposed limestone available for colonization, with topographical complexity also important. An investigation of the influence of water quality suggests that suspended solids (silting) is a significant determinant of lichen distribution together with eutrophication.

Punctelia perreticulata (Räsäanen) G. Wilh. & Ladd is recognized as a distinct species. The only consistent differences between P. perreticulata and P. subrudecta (Nyl.) Krog are the shape and length of conidia. Both species are widespread in the world. In P. perreticulata, there are differences in conidial length among the European, American and Australasian samples studied, but they neither correlate with differences observed in other morphological traits nor with the substratum. An epitype is selected to support the holotype of P. perreticulata, because its identity is uncertain due to the absence of conidia.

Skomer Island, a National Nature Reserve, lies off the West coast of Wales. This small island holds lichen communities of international importance associated with large populations of seabirds. Saxicolous lichen communities are described, 248 species listed and details given of a base-line monitoring programme, which will provide data on changes in the lichen flora over time and distinguish cyclical from permanent deleterious changes. Threats to island populations are discussed, such as the likely effects of oil pollution following the Sea Empress accident in February 1996.

The thermocouple psychrometer was used to determine water potential, Ψ and its components in the lichen Parmotrema tinctorum. Data suggested that using conventional pressure-volume curves to study the water relations of lichens may give anomalous results, possibly because lichens may contain appreciable amounts of intercellular water. A way of correcting pressure-volume curves to remove the effect of intercellular water is discussed. Parmotrema tinctorum had a very low osmotic potential at full turgor (c. −2.5 MPa), and a low bulk modulus of elasticit (c. 2.1 MPa). As a result, P. tinctorum lost turgor only when the relative water content dropped below 0.47. Likely benefits of this for the lichen are discussed.

Measurements of modulated chlorophyll a fluorescence emission and chlorophyll content were made in thalli of Parmelia quercina collected from northern Castellon(Spain). Althoug high air pollution concentrations have been measured in this area, the ratio of variable to maximal fluorescence is unaffected. Following dark-adaptation, the response to irradiance of chlorophyll fluorescence was examined. With respect to control samples, thalli collected in northern Castellon consistently showed differences in fluorescence quenching, the efficiency of excitation energy capture and quenching of basal fluorescence. However, the quantum ield of photochemistry and non-cyclic electron flow were not affected. The changes in chlorophyll fluorescence parameters were observed in the absence of both visual injuries and decrease in chlorophyll content. The results are discussed with regard to the possible role of environmental stress in chlorophyll fluorescence yield.

Nine specimens of Pyrenula japonica Kurokawa were collected from various areas in Japan. Photobionts were isolated from their thalli and studied taxonomically. As a result, only one species of green alga,Trentepohlia lagenifera(Hild.) Wille was identified as the photobiont of Pyrenula japonica. This is the first record of this alga from the lichen genus Pyrenula.

The importance of mineralogy in determining lichen assemblages occurring on metalliferous rocks and derived soils is discussed with reference to environments enriched in metals from mine and smelter wastes and other sites involving human activities. A study of lichens growing on Cu and Fe sulphide-rich rocks in Scandinavia is presented. This data suggests that the composition of the lichen communities is governed by mineralogy, which influences the mobility and availability of Cu2+ and Fe2+ in the environment, rather than the total concentrations of either metals within the substratum. A new lichen community, the Lecideion inopis Purvis, is described characterized by the faithful species Lecidea inops, Psilolechia leprosa and several Cu-rich ecotypes. This community occurs alkaline environments where Cu is fixed predominantly as a secondary hydroxide or carbonate. Conversely, low pH, Fe sulphide-rich environments, where Cu may also be present, are characterized by the Acarosporion sinopicae, which includes several species with a rusty colouration. Contrasting assemblages rich in terricolous ephemeral species, especially Vezdaea spp. occurring in Pb/Zn-rich environments, and the comparatively species-poor assemblages on Cr and Ni-rich ultrabasic rocks, are also reviewed. Although mine spoil heaps and other mineralized environments are perceived in human terms as toxic, they may support a diversity of lichens, including rare taxa restricted to these sites. The systematic description of these lichen communities in relation to rock mineralogy and chemical processes are necessary if physiological tolerance and speciation are to be understood.

Lichens were cultured by attaching a thallus fragment to a nylon monofilament loop with silicone sealer. Two effective methods for adjusting lichen mass to a standard moisture content were developed (the ‘reference-sample’ and ‘sacrificial’ methods). These corrections for moisture content allow detection of very small changes in dry mass without having to oven dry (and kill) all transplants. Average annual biomass growth rates for non-fragmenting species were typically between 5 and 30%. Annual biomass growth rates of healthy, vigorous individuals, as indicated by the 75th percentile, were mostly between 10 and 40%. Alectoria sarmentosa was prone to fragmentation despite the maintenance of healthy thalli. The other species can be ranked by biomass growth rates as follows: Evernia prunastri> Lobaria pulmonaria=Usnea longissima> Pseudocyphellaria rainierensis=Lobaria oregano.

The FV/FM ratio of Lobaria pulmonaria with decreasing pH in samples from a boreal forest influenced by acid rain in SE Norway, suggesting that low pH has an effect on the optimal quantum yield of PSII. The pH was measured of distilled deionized water in which lobes from different habitats were rinsed, probably indicating the ionic environment of the lichen. The best prediction of FV/FM was found in a multiple regression model including the explanatory variables: pH, a/b-ratio and chlorophyll degradation measured as the 666/666a ratio, all correlated positively with FV/FM but not with each other. The commonly used chlorophyll degradation 435/415 ratio cannot be used for L. pulmonaria because of an unidentified, habitat-influenced brownish pigment with high absorbance in the 415–435 nm wavelength range.

The cyanobiont (Nostoc) of the lichen Peltigera horizontalis was isolated using a procedure of repeated grinding, differential centrifugation and partitioning in an aqueous two-phase system of dextran/polyethylene glycol. A yield of 22% was calculated on the basis of chlorophyll recovery from the thallus. Freshly isolated Nostoc differed little from that kept in prolonged culture with respect to the relative activities of a number of enzymes of carbohydrate metabolism in the soluble fraction. However, much higher specific activities of the disproportionating transglycosylase and starch phosphorylase, higher intracellular concentrations of glucose, maltooligosaccharides and glycogen and a lower rate of glucose uptake were evidentin freshly isolated Nostoc. These activities and pool sizes, as well as CO2-fixation capability, stayed roughly constant for at least 5 h after isolation; glucose release, which is characteristic for the symbiotic Nostoc, dropped sharply within 1 h. These observations suggest the transport of glucose out of the cell, rather than that theactivities of cytoplasmic enzymes may bea point of early regulation during transition of Nostoc from the lichenized to the free-livingstate.

Snow meltwater containing 36 ng ml−1 NO3−−N (raised here to between 95–101 ng ml−1 NO3−−N) and 112 ng ml−1 NH4+ −N was sprayed onto illuminated Usnea sphacelata at 2°C in a 2−1 capacity transparent perspex chamber force-ventilated with either air or O2− (and CO2−) free N2. The NO3-concentration in meltwater recirculated through a layer of U. sphacelata fell to c. 8 ng ml−1 after 1.25 h. Although the pattern of decline was broadly comparable in both air and N2, the initial rate of decline was lower in N2. When undepleted meltwater was continuously sprayed onto the lichen and the effluent collected for analysis, the lichen was found to retain 55% of the wet deposited NO3− in air but only 27% under N2. Up to 90%) of NH4+ supplied in a continuous spray of meltwater was retained by the lichen but this was affected little by O2 and CO2 deprivation.

Surface alkanes were extracted from thalli of populations of Xanthoria parietina growing in two different Piedmont (Italy) valleys: Susa and Vermenagna. The main n-alkanes detected in the Susa Valley were C27, C28, C29 and C31, whereas C25, C27 and C29 were the most abundant in Vermenagna Valley. The results indicate that the n-alkane qualitative composition of X. parietina was affected both by elevation and climatic characteristics typical of the two valleys considered.

Epiphytic lichen and bryophyte species composition, richness and diversity were surveyed on basal trunks of six common old-growth forest tree species, Picea abies, Pinus sylvestris, Betula pendula, Alnus incana, Salix caprea and Populus tremula, in two old-growth forest areas, one in southern and one in middle boreal Finland. The average species numbers per tree ranged from 18 (Picea) to 27 (Salix) in the southern and from 20 (Populus) to 31 (Salix) in the middle boreal area. A few widespread habitat-generalist species, such as the foliose lichens Hypogymnia physodes and Platismatia glauca, were most abundant on all the tree species, except Populus. Most other epiphyte species showed at least a slight preference for one or two tree species. Populus proved to have the most distinct flora characterized by the abundance of certain, rather specialized crustose lichens and bryophytes. The number of species that occurred on only one tree species was highest on Populus (9) in the southern and on Alnus (18) in the middle boreal area. Differences in bark acidity and structure were the most likely explanations for the differences between tree species in the epiphytic flora and diversity. Salix and Populus were the most important of the tree species studied for the conservation of epiphyte diversity in the boreal forests of Finland.

Cladina subtenuis is the most commonly found ‘ reindeer lichen ’ in the southeastern United States. In the present study C. subtenuis was examined for polymorphism in the small subunit (SSU) ribosomal DNA (rDNA) within and among small clumps of podetia, here referred to as mats, from five geographical locations. Polymorphism in the SSU rDNA was not detected among podetia within mats, but polymorphism was detected among mats from a single location. Therefore, mats of C. subtenuis may represent a single genetic individual, although genetically distinct mats may occur in close proximity. Their proximity couldencourage sexual reproduction between genetically distinct individuals, which would maintain variation in these populations. The SSU rDNA types represented three different lengths and restriction-site patterns, reflecting the presence of sequence insertions of at least 200 nucleotides in the SSU rDNA coding region. Thei nsertions, differing in position, number and sequence, are group I introns similar to those previously reported in the Cladonia chlorophaea complex. The intron variation among the SSU rDNA types indicates that molecular evolution has occurred within this species, perhaps since its divergence from related taxa and dispersal across the southeastern United States.