Primary production in lichens, as in all plants, is the result of gains and losses. Losses of carbon may be high under extreme environmental conditions. In the harsh climate of polar regions lichens use much carbon for maintenance and in their stress response. Thallus biomass is preserved through periods of darkness, extremely low temperatures and snow cover. On the other hand, lichens are photosynthetically active at temperatures below 0°C. They can make use of melted water from snow and ice and take up water vapour from snow. Physiological adaptations and environmental conditions under which growth is possible are discussed in terms of our recent results. A concept model describes the main parameters that influence carbon acquisition, growth and water relations of lichens in polar regions.

The Caloplaca holocarpa group in the Nordic countries, except Iceland, is defined genetically using the nrlTS DNA gene. The members are analysed with regard to morphology, anatomy, ecology, and chemistry. The results show that C. holocarpa seems to be a very small group, but there are many morphologically similar species outside the group. Within the group several species have been confused, but it is shown that C. holocarpa, C. pyracea, and C. vitellinula are separate taxa. Caloplaca cerinella also belongs to the group whereas C. cerinelloides does not, but is included in the treatment because of its similarity to the former species. Caloplaca lithophila H. Magn. is a synonym of either C. holocarpa or C. vitellinula, most probably of the latter. Many specimens determined to C. holocarpa belong to Caloplaca oasis, but this species is shown to have much more variable morphology and wider ecology and distribution than previously understood. Caloplaca oasis has also been confused with C. polycarpa, which is similar, but morphologically and genetically distinct, even though related. Neither of the two species belong to the C. holocarpa group, but are related to the C. citrina group, not to the C. velana group as usually believed. Other species from northern and central Europe similar to C. holocarpa belong in other groups. The treated species are described and illustrated in colour. Distribution maps are given for the study area. A key to species in northern Europe similar to C. holocarpa is also provided.

Xanthona parietina thalli were collected from a ‘clean-air’ location and from a polluted area. Ramalina duriaei thalli were collected from the same ‘clean-air’ location and some thalli were transplanted to air polluted locations, where R. duriaei no longer occurs. The effects of air contaminants on these two lichens were compared under controlled laboratory conditions and in field experiments. Air contaminants and exposure to bisulphite ions had little or no damaging effect on X. parietina, whereas severe damage was caused to R. duriaei, as judged by chlorophyll degradation, autofluorescence of photobionts, photosynthetic activity, membrane integrity and ATP content. The different responses presented confirm the sensitivity of R. duriaei and resistance of X. parietina to air pollution.

Dirina (Roccellaceae, Arthoniales) is a monophyletic genus of crustose, saxicolous or corticolous lichenized fungi. Twenty-four species are accepted in the genus, including nine new species: Dirina angolana, D. arabica, D. astridae, D. canariensis, D. indica, D. madagascariensis, D. pacifica, D. pallescens and D. sorocarpa. A phylogenetic hypothesis is presented based on data from four molecular markers, β-tubulin, ITS 1 and 2, nuLSU and RPB2, including all recognized Dirina species worldwide. New combinations proposed include Dirina badia for Roccellina badia, Dirina jamesii for Roccellina jamesii, Dirina candida for Chiodecton candidum and Dirina teichiodes for Lecidea teichiodes. Two species are reinstated: Dirina approximata and D. monothalamia (as a new name of Chiodecton africanum). Asexual morphs described earlier at the rank forma are no longer recognized as taxonomic units viz., Dirina catalinariae f. sorediata, D. insulana f. sorediata, D. massiliensis f. sorediata, D. paradoxa ssp. paradoxa f. sorediata and D. massiliensis f. aponina. One species, Dirina calcicola, is transferred to Fulvophyton and two other species, Dirina insulae-howensis and Dirina neozelandica, are transferred to Schismatomma. Dirina follmannii is not accepted in Dirina and placed as incertae sedis. A key to the species of Dirina is provided. Vicariance through plate tectonics and continental drift versus long distance dispersal to explain biogeographical patterns is discussed.

Samples of Hypogymnia physodes were transplanted to the environment of the former uranium mine at Žirovski vrh, Slovenia for two exposure experiments. The levels of the long-lived radionuclides, 238U, 226Ra and 210Pb in lichen material were measured after 4 and 7 months in the first experiment, and 4, 8 and 12 months in the second, and compared with the levels in lichens growing in-situ from the same sampling locations. They were also compared with the nuclide levels found in air particulates by gamma spectrometry obtained at the regular site monitoring stations. The results showed that each of the radionuclides had its own distribution pattern in this environment. The highest 226Ra levels were found in lichens in the near vicinity of the dry-tailings pile, while U concentrations were high in the valley of the confluence of the Todraščica and Brebovščica streams close to the former yellow-cake production plant in Todraž, and then decreased downstream. 210Pb was the most uniformly distributed radionuclide and exhibited the highest level. The results also confirm that active biomonitoring with transplanted lichens can be a useful and cheap supplement to instrumental air pollution monitoring.

The origin and development of pseudocyphellae and the pored epicortex are compared. Pseudocyphellae are pores through the paraplectenchymatous cortex which fill with medullary hyphae. The pored epicortex is a thin, perforated polysaccharide sheet lying over a loosely organized cortical layer. Both structures function in gas exchange and may represent two different phyletic lines.

The first molecular phylogenetic study on a range of Punctelia species is reported, focussing on specimens growing in the Iberian Peninsula. Material of seven species was included in the analysis. Forty sequences were generated from nuITS and mtSSU rDNA in 20 specimens, and the resultant majority rule consensus tree from the combined analyses shows four major clades. Punctelia ulophylla is confirmed as a distinct species, P. reddenda is basal to P. borreri, and P. perreticulata groups with P. subrudecta. Samples identified as P. rudecta from the Canary Islands and China occupy different basal positions; the complex merits further study. Punctelia borreri and P. subrudecta are mainly coastal in the Iberian Peninsula, but are now reported from the central plateau for the first time; newly colonizing thalli have been found in a park in Madrid which is regularly spray-watered and where sulphur dioxide levels have fallen over the last two decades.

Morphological, anatomical, chemical and ecological evidence show that the South African lichen Roccellina capensis (Nyl. ex Stizenb.) Tehler has developed a dispersal strategy with either sexually dispersed individuals, or vegetatively dispersed, sorediate individuals, hence a putative species-pair. The concept ‘species-pair’ is well-known and widely used in lichenology. It refers to closely related, morphologically indistinguishable lichens that differ from each other by their dispersal strategies only. The so-called ‘ primary species ’ produces fruiting bodies and sexual spores, while its counterpart, the ‘ secondary species ’ is vegetatively dispersed by soredia, isidia or fragmentation. Our study uses molecular information to investigate if R. capensis should be treated as a species-pair or not. The internal transcribed spacer (ITS) of the nuclear ribosomal DNA was sequenced for 17 specimens of R. capensis in order to test if sexual and asexual (sorediate) specimens would group into two distinct, monophyletic groups. Such grouping would support their recognition as separate taxa in a species-pair. We also investigated whether the randomly amplified polymorphic DNA (RAPD) method would be a suitable procedure in population studies of lichens. The analysis of the ITS region produced a single most parsimonious tree. The sexual and asexual specimens were grouped according to their geographical distribution, rather than according to their dispersal strategy. This result clearly shows that the sexual and asexual specimens ofR. capensis do not represent a species-pair. The RAPD data set produced an almost completely unresolved tree due to several homoplasious characters, possibly a result of algal contamination.

The first modern taxonomic classification of the species of Lepraria is presented. Chemistry is the most important character used to separate the morphologically similar, but distinct, sterile taxa. Nine species are recorded from the British Isles, of which L. eburnea and L. frigida are new to science. Lepraria nivalis is a new name for Crocynia murorum B. de Lesd., and L. caesioalba (B. de Lesd.) Laundon a new combination. Two species, L. incana (L.) Ach. and L. lobificans Nyl., are especially common and are dominant on shaded bark and rock. Twenty-eight lichens reported as Lepraria belong elsewhere or require further study. The combination Leproloma cacuminum (Massal.) Laundon is made to replace the name L. angardianum.

Molecular sequence data of the nuclear ITS region was used to investigate the diversity of photobionts in Polish samples of Flavocetraria nivalis. The samples came both from alpine habitats, as well as from lowland localities near the coast. All green algal symbionts were identified as members of the Trebouxia simplex aggregate. These were compared with those of additional samples from Flavocetraria nivalis collected in different parts of Europe and also with photobionts assigned to T. simplex from other lichens. Within the T. simplex aggregate, the Trebouxia ITS sequences from F. nivalis formed four clades. In the Polish lowland populations only a single clade of T. simplex was detected which also occurs in Polish mountains, south Sweden and Austria. A further clade of T. simplex is present in F. nivalis from Polish mountains and is also known from F. nivalis further north in Scandinavia and Greenland, as well as from other lichens in Sweden, the Austrian Alps, and Antarctica.

This study compares the success of vegetative diaspore establishment of the old forest lichens Lobaria pulmonaria and L. scrobiculata sown on Picea abies branches in boreal rainforests. The larger diaspores of L. pulmonaria (green algal photobiont) established more successfully, and showed a greater flexibility in ecological amplitude, than the smaller diaspores of L. scrobiculata (cyanobacterial photobiont). The establishment success apparently depended on species-specific differences in morphological and physiological traits of the diaspores. Both species established as well in young plantations as in old forests. Lobaria scrobiculata was most successful on short branches and small trees. In contrast, L. pulmonaria responded positively to trunk circumference in the old stands. The establishment success of both species decreases with increasing canopy openness, indicating that the soredia/isidioid soredia failed to establish on the most exposed branches. The probability of establishment did not change with bark-pH or with distance from the nearest stream. Despite a successful establishment in regeneration forests, the long-term survival in managed forests is still uncertain.

Synthetic thalli of Usnea strigosa produced the same fibril morphology and secondary compounds as natural thalli. The outer cortex of synthetic lichens was covered with crystals of usnic acid and compounds related to norstictic acids. The common presence on the fibrils of lichen acids suggests that these compounds have a functional role in the symbiosis. During alcohol dehydration, crystals of usnic acid dissolved and left impressions in the mucilage around the symbionts. The impressions were valuable indicators of the position of crystals in the lichen thallus. Crystal impressions of usnic acid were common on the cortical hyphae and were seen also on the surface of algal cells. The crystal impressions were larger in the synthetic lichen than in natural thalli. Impressions of norstictic acid and related compounds were not seen.

Four new species and one new forma are described in the genus Porpidia. Porpidia flavocruenta Fryday & Buschbom, a member of the P. macrocarpa group that has previously been overlooked for ‘P. flavocoerulescens’, is reported from Austria, the British Isles, Scandinavia, Iceland, and North America (Alaska); P. islandica Fryday, Knoph & Hertel is reported from Iceland and Scotland; and P. pachythallina Fryday and P. striata Fryday from the British Isles only. The sorediate morph of P. superba is described as P. superba f. sorediata Fryday, known from the British Isles, Sweden, Svalbard, and North America (Maine). Variation in P. macrocarpa is discussed and the new combination P. macrocarpa f. nigrocruenta (Anzi) Fryday made. Secondary metabolite production is discussed and the variation in the production of chemosyndromes considered to be more variable than previously reported. The position of several other taxa is discussed and P. herteliana and P. musiva are reduced to synonymy with P. cinereoatra, P. calcarea to synonymy with P. superba, and P. diversa to synonymy with P. contraponenda. However, P. grisea and P. lowiana are provisionally maintained as distinct species from P. tuberculosa and P. cinereoatra respectively, although P. grisea has not been correctly recorded from the British Isles. The typification of Spiloma tuberculosa Sm., the basionym of Porpidia tuberculosa, is discussed and a lectotype proposed; the new combination Porpidia rugosa (Taylor) Coppins & Fryday is made and shown to be the correct name for P. glaucophaea; and Porpidia flavicunda (Ach.) Gowan is used for the esorediate taxon usually known as Porpidia flavocoerulescens because this epithet is to be proposed for rejection as it is considered to be of confused usage. Porpidia hydrophila is shown to be a member of the P. albocaerulescens group. Porpidia lowiana, P. nadvornikiana, and P. thomsonii are recorded for the first time from the British Isles, and P. macrocarpa f. nigrocruenta confirmed as a British taxon. Notes and a key are provided for all the species of the genus that have been reported from the area.