Canopy lichen abundance was assessed by size class on regenerating hemlocks, comparing trees of similar size and age (c. 120–140 yrs) growing in the understorey of old-growth cedar-hemlock stands with those growing in adjacent even-aged hemlock stands (natural origin patches c. 1–3 ha in size). Five chlorolichen taxa were associated with old-growth understorey trees: Cavernularia hultenii, Hypogymnia vitatta, Parmelia hygrophila, Platismatia norvegica, and Usnea spp. Lobaria pulmonaria was the most abundant cyanolichen on regenerating hemlock in the old-growth forest stands, particularly in lower canopy (under 12 m) exposures. However, other cyanolichen taxa such as Nephroma helveticum, Sticta fulginosa, and Pseudocyphellaria anomala, reached their greatest abundance at mid-canopy (12–24 m) positions. Smaller cyanolichen thalli (<9 cm2) were abundant on regenerating hemlocks across all canopy positions in the old-growth forest, raising the question as to whether or not cyanolichen thalli in mid- to upper-canopy environments represented long-established individuals facing severe growth constraints, or were simply thalli that had experienced higher rates of fragmentation, and thus did not achieve larger sizes. In comparison, cyanolichens of all taxa were essentially absent from the small-patch even-aged forest stands. Given that dispersal of propagules was not likely a major limiting factor, these 120–140 year old even-age stands may not yet have attained sufficient old-growth characteristics (especially canopy microclimate and canopy throughflow enrichment) to support cyanolichen growth. These findings have major conservation biology implications for wet interior cedar-hemlock forests in British Columbia, where forest harvesting is creating a mosaic of even-aged stands, whose projected age at the time of next harvest (rotation age) will be 120 years or less.

The phylogeny of the Micarea prasina group was investigated using mitochondrial small subunit ribosomal DNA sequences from 14 taxa representing this group, four other members of the genus Micarea, and Psilolechia lucida as an outgroup. A total of 31 new mtSSU rDNA sequences were generated, including 10 from the M. micrococca complex. Bayesian, maximum parsimony (MP) and maximum likelihood (ML) methods were used to analyse the data. The results show that M. micrococca is not monophyletic and forms three strongly supported lineages: 1) M. micrococca s. str., 2) M. byssacea (Th. Fr.) Czarnota, Guzow-Krzemińska & Coppins comb. nov., and 3) a putative taxon that requires further studies. Micarea viridileprosa is a sister species to M. micrococca s. str. and the recently described M. nowakii is a sister species to M. prasina s. str. The placement of M. tomentosa within the M. prasina group is confirmed. Micarea hedlundii appears to be more closely related to the M. micrococca complex than M. prasina s. str. Descriptions, illustrations, taxonomic remarks, distribution and habitat data for M. micrococca s. str. and M. byssacea are provided. A lectotype for Biatora byssacea Hampe non Zwackh and a neotype for Catillaria prasina β [var.] byssacea are selected.

The cell wall composition of several species of the lichen phycobionts Trebouxia and Pseudotrebouxia has been investigated using gas chromatography, thin layer chromatography and infrared absorption spectrophotometry. In addition cell wall components (cellulose, non-cellulosic polysaccharides, sporopollenin, protein) were localized with cytochemical methods at the EM- level. The cell walls of Trebouxia and Pseudotrebouxia consist of several layers. In Trebouxia the inner layer (Si) consists mainly of cellulose, then followed by a non-cellulosic polysaccharide layer (S2), a sporopollenin-layer (S3) and an outer layer consisting again of a non-cellulosic polysaccharide (S4). In addition Trebouxia is surrounded by a sheath (a polysaccharide with species-specific terminal residues). In Pseudotrebouxia the cell wall is similarly constructed compared to Trebouxia, however, the sheath is lacking and the S4 layer contains a polysaccharide with species-specific terminal sugar residues. The role of the different cell wall constituents for the recognition mechanism between the lichen symbionts is discussed.

The lichenicolous Phoma species on Cladonia are revised. A statistical analysis of the conidial size suggests that three species are involved: P. cladoniicola sp. nov. a common and widespread species in the Northern Hemisphere occurring on a wide range of Cladonia species; P. foliaceiphila sp. nov. known from C. foliacea and C. fimbriata in Europe; and P. grumantiana sp. nov. known from C. symphycarpia and C. mateocyatha in Svalbard and the USA.

Parmelina tiliacea is a common, widely distributed species in south-western Europe, easily identifiable by morphology and much used as an air pollution bioindicator in many regions. A molecular phylogenetic survey of samples from many geographical areas, using Maximum Parsimony and Bayesian inference of nuITS and mtLSU rDNA regions, revealed a group of samples geographically restricted to a small region of the Iberian Peninsula and genetically separated from the other P. tiliacea specimens studied. These samples are morphologically indistinguishable from P. tiliacea, apart from subtle anatomical characters in the ascomata (hyphae of the exciple and ascospore width), which are frequently absent. Although geographically different, the two taxa occupy similar habitats and are even sympatric in some areas, indicating that they do not exchange genetic material. This previously overlooked, and apparently endemic lineage, is described as P. cryptotiliacea sp. nov., and the name Lichen tiliaceus is epitypified by a sequenced specimen to fix the application of Parmelina tiliacea to the widespread genotype. A second unexpected result was the discovery that the morphologically distinct P. pastillifera was nested within P. tiliacea. These two cases stress the need to use molecular tools to elucidate species concepts even within widespread morphologically well-characterized macrolichens. Such investigations are necessary to improve our understanding and estimation of biodiversity, and to facilitate the development of sound biodiversity conservation strategies for lichens.

The major works on British lichens published between 1724 and 1780 are briefly reviewed. The new lichens published in Withering's Botanical Arrangement of 1776 have been mostly overlooked; they were based on species described by Dillenius. These lichens are typified here, along with Withering's new lichens published in later editions of the Arrangement. Altogether 41 species are reviewed. The following 16 new combinations based on Withering's species are presented, with synonyms in parenthesis: Anaptychia runcinata (A.fusca), Caloplaca crenularia (C. festiva), Qadonia humilis (C. conista, C. conistea, C. conoidea), Qadoniapeziziformis (C. capitata), Cladonia ramulosa (C. anomaea, C. pityrea), Collema auriforme (C. auriculatum), Collema dichotomum (C. fluviatile), Collema fuscovirens (C. tuniforme), Dermatocarpon luridum (D. aqualicum, D. weberi), Leptogium gelatinosum (L. sinuatum), Lobaria virens (L. laetevirens), Peltigera didactyla (P. spuria), Peltigera lactucifolia (P. hymenina), Physconia distorta (P. pulverulacea), Ramalina lacera (if. duriaei), and Tornabea scutellifera (T. atlantica).

Later names affected by Withering's taxa are also investigated, and 12 are shown to be nomenclaturally superfluous. Other names are later homonyms, with the result that seven species require change of author citation as follows: Dactylina madreporiformis (Ach.) Tuck., Lecanora crenulata Hook., Psora lurida (Ach.) DC, Ramalina polymorpha (Liljeblad) Ach., Solorina spongiosa (Ach.) Anzi, Stereocaulon ramulosum Rauschel, and Sticta fuliginosa (Hoffm.) Ach.

The nomenclatures and systematic position of Cladonia conista C. Robb. ex Allen nom. illeg., Cliostomum griffuhii (Sm.) Coppins, Leptogium palmatum Mont., Lichen squamatus Dickson, Pachyphiale cornea (Ach.) Poetsch, and Pycnothelia papillaria Dufour is discussed, the correct name for Leptogium palmatum being L. corniculatum (Hoffm.) Minks and for Pachyphiale cornea being P. carneola (Ach.) Arnold. A history and account of Withering's herbarium is included.

A significant negative correlation was found between the quantity of acetone-extractable phenolic compounds and the degree of enzyme polymorphism in eight eastern North American populations of Umbilicaria americana. In sites higher elevations, where UV irradiance was more intense, phenolic levels were significantly lower and within-stand enzyme variability significantly greater than in low elevation sites. Similarly, the phenolic content of thalli collected in Ontario, Canada, over a 16-month sampling period was negatively correlated with mean monthly UV-B irradiance.

The ultrastructure of the symbionts within the algal layer of Lasallia hispamca and Umbilicaria spodochroa has been investigated by applying stereological techniques to quantify cellular organelles and structures. The stereological parameters calculated were volume density (Vv) and surface density (Sv). To obtain these parameters for each cellular structure, a systematic sampling of photographic fields of the algal layer for each sample was utilized.Significant differences between the two lichen species with respect to both symbionts were observed. The cellular structures of the photobiont that differed the most between the two lichen species were the chloroplast, which differed by 15°0, in the Vv values and 25°0, in the Sv values, the pyrenoid (as a whole and in the diameter of pyrenoglobuli) and the mitochondria. With respect to the mycobiont, the vacuolar apparatus was of great importance in characterizing the two species, as was to a lesser extent the protoplast volume occupied by concentric bodies.

Phenotypic characters, either morphological or chemical, have shown to be insufficient to delimit species boundaries in the genus Cladonia. The present study addresses the circumscription of species within the Cladonia cariosa group, examining a number of specimens of the currently accepted taxa Cladonia cariosa, C. symphycarpa, C. acuminata, C. subcariosa and C. latiloba. We employed maximum likelihood and Bayesian methods of phylogenetic reconstructions based on DNA sequences of ITS, rpb2 and ef1α regions. Our results show that the C. cariosa group consists of at least four phylogenetic lineages. It is also shown that each of these lineages is chemically variable, which restricts the taxonomic value of the chemical differences within the group. However, anatomical differences, such as squamule surface and cortex structure, were found to correlate with the distinct lineages found in the phylogenetic analysis. This result confirms the taxonomic value of the cortical surface under SEM, as was found in other lichen groups.

The lichen colonization of recently created urban wasteland is described by referenceto 40 sites in England, Scotland and Wales. The 100 species encountered form a series of overlapping communities in which successional relationships over the first 16 years have been investigated. Floristic variation within towns tends to be greater than variation between them. Ona national scale climatological, geological and historical factors appear to play only a small part in determining the composition of this pioneering flora. Many species can be accommodated within the strategy group stress-tolerant ruderals; a few possess the character of ruderals. The heyday of this component of the urban flora may be drawing to a close. Acarospora heppii f. luteopruinosa, Lecidea polycarpella and Micarea excipulata are reported as new to Britain.

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.

Based on findings in vascular plants showing that the capacity to provide enough carbon skeletons for rapid ammonium assimilation into amino acids is a prerequisite for tolerance to eutrophication, we tested the hypothesis that lichens from shady habitats are particularly sensitive to nitrogen pollution. We tested this hypothesis using published ecological indicator values (estimates of eutrophication tolerance and light preferences on an ordinal scale) for more than 500 central European lichen species. Our results show that shade-adapted lichens are indeed at the same time intolerant to eutrophication. However, not all eutrophication-sensitive lichens inhabit shady environments, suggesting the existence of several independent mechanisms causing intolerance of high nitrogen levels in lichens. The correlation of shade adaptation with nitrogen intolerance is limited to epiphytic and saxicolous species, since terricolous lichens are out-competed by vascular plants in dense vegetation. Our results suggest that lichen communities of shady bark, wood and rock are particularly sensitive to eutrophication.

Axenic, spore to spore resynthesis of Xanthoria parietina has been accomplished on an agar substrate.

A community ecology approach using an association of species test and a principal component analysis resulted in the recognition of two major and two minor foliicolous lichen communities in a neotropical rainforest. The major communities arc governed by microclimatic factors, one characteristic of the shady understorcy and the other confined to light gaps. The minor communities are due to subtle phorophyte preferences towards palm and dicot leaves. The shady understorey community is dominated by the families Anhoniaceae, Opegraphaceae, Tnchoihdiaceae and Pilocarpaceae, which predominantly have Phycepeltis as their phycobiont, thin thalli, abundant sexual reproduction, small ascospores produced in high numbers, and pyenidial conidiomata. The light-gap community is mainly composed of the families Gomphillaceae and Ectolechiaceae, with Trebouxia as their phycobiont, thickly crystalline or whitish, dispersed thalli, frequent asexual reproduction, large ascospores produced in low numbers, and specialized campylidia and hyphophores as conidiomata. Phycobiont, thallus structure, and the mode of reproduction are considered as adaptations to different microsites, whereas the shape and size of ascospores and conidia seem to be of less importance. The foliicolous lichen communities reflect the spatial and temporal structure of the forest, in particular the continuity of the shady understorey in comparison to the discontinuity of the light gaps. While the formation of the shady understorey community follows more deterministic patterns, the light-gap community exhibits high stochasticity.