Changes in habitat affect the distribution of species at different spatial and temporal scales. Our aim was to assess the use of several retrospective methods when determining habitat history and its influence on species distribution, using the pendent lichen Usnea longissima Ach. as a model organism. The study was carried out in a Norway spruce dominated forest, located in the middle boreal zone of northern Sweden. Historical sources (including forest inventories and maps) and dendrochronology were combined with field surveys to determine past stand characteristics with a high spatial precision. Also, present stand characteristics were thoroughly surveyed and the relationship between distribution of U. longissima and past and present habitat characteristics were evaluated. Our results showed that, despite the fact that historical logging was unevenly distributed within the study area, similarities in stand structure exist today. Several essential factors affecting the distribution of U. longissima could be related to changes in past stand structure, especially the extent and intensity of previous logging operations and the subsequent stand development during the last c. 150 years. Our results also showed that U. longissima was favoured by a continuous old age structure with canopy openness preserved. The importance of detailed reconstructions of specific habitat components is highlighted when relating species presence to habitat change. It is suggested that the use of retrospective methods presented in this study can be helpful in clarifying possible causes for the complex distribution of certain organisms.

Pyrenulaceae is one of the dominant lichen families in the tropics, especially in lowland evergreen forests. Although very species-rich, phylogenetic relationships within Pyrenulaceae have not been extensively studied using molecular data, and its morphology-based generic delimitation remains untested. A recent lichenological survey carried out in the Knuckles Mountain Range in Sri Lanka allowed the first author to collect fresh specimens of different species of Pyrenula, and to investigate the phylogenetic relationships within the family Pyrenulaceae using a multigene analysis (ITS, nuLSU and mtSSU) and a preliminary dataset of 21 taxa. This data shows that the family Pyrenulaceae can be divided into two well-supported groups and suggests that the genus Pyrenula is not monophyletic. Characters usually used for generic classification in this family (ascospore colour and septation, structure of the ascospore locules, secondary chemistry, hamathecium structure, ostiole position) do not correlate with these two groups. However, the presence of pseudocyphellae is restricted to species of Pyrenula from one group.

The lichen genus Chrysothrix Mont, is shown to comprise four species: C. candelaris (L.) Laundon comb, nov., C. chlorina (Ach.) Laundon comb, nov., C. chrysophthalma (P. James) P. James & Laundon comb, nov., and C. pavonii (Fr.) Laundon comb. nov. (C. noli-tangere (Mont.) Mont.). The genera Pulveraria Ach. and Temnospora Massal. are placed in the synonymy of Chrysothrix nom. cons., and all bright yellow, leprose, sterile lichens with pulvinic acid derivatives, formerly included in Lepraria and Crocynia, are referred to the genus. Chrysothrix oceanica Rasanen is excluded; it probably belongs to Caloplaca. A key to and detailed accounts of the recognized species are included. There are three chemotypes of Chrysothrix candelaris, one of which is probably of hybrid origin.

Three long-term studies of lichen growth and colonization have been undertaken at Signy Island, South Orkney Islands, in the maritime Antarctic. Small individual thalli of several crustose species and uncolonized plots on 12 fresh rock surfaces were photographically monitored at intervals of 3–4 years over a period of up to 20 years. The development of Ochrolechia frigida colonies on a regenerating moss bank, recently uncovered by a receding glacier, was similarly monitored. The results indicate that many lichens growing in sites enriched by nitrogenous compounds derived from populations of sea birds, have relatively rapid colonization and growth rates. Mean percentage increase in thallus area can be as high as 15–32% per annum in some nitrophilous saxicolous species (e.g. Acarospora macrocyclos, Xanthoria elegans and species of Buellia and Caloplaca), but as low as, 0·4–4% in nitrophobous species (Lecanora physciella, Lecidea sp., Rhizocarpon geographicum). Umbilicaria antarctica and Usnea Antarctica also yielded data indicating high growth rates, with colonist plants reaching several centimetres after 20 years. Colonization by mixed assemblages of lichens of new rock surfaces can attain 40->90% cover after 20 years in nutrient-enriched sites, and even 20–25% in non-biotically influenced sites. Colonization by or increase in extant O. frigida on the regenerating moribund moss bank was also quite rapid. It is suggested that the exceptionally large thalli of several lichen species and the locally extensive dense lichen fellfield communities in the maritime Antarctic may be much younger than previously supposed.

The thallus structure of a common epiphytic lichen Hypogymnia physodes growingon the bark of Pinus sylvestris under a variety of microclimatic conditions was studied by means of fluorescence and scanning electron microscopy. The disparity between the thallus layer thicknesses of specimens growing in different habitats proved to be small though obvious, and differences also appeared in the amount of gelatinous substances in the hyphal cell walls ofthe cortex and algal layer. Furthermore, the occurrence of a pored epicortex of H. physodes at dry sites is reported. The size distribution of the thalli, thallus area and the production of soralia showed a complex interaction with microclimate. Against a background of the microclimatic data collected here, humidity is considered to be the most important factor affecting the anatomy and morphology of the thallus.

The new generic name Lichenothelia nom. nov. is introduced for the Microthelia aterrima group which proves to be unrelated to the corticolous mainly nonlichenized fungi generally referred to Microthelia. Two species are accepted, Lichenothelia metzleri (Lahm) comb. nov. and L. scopularia (Nyl.) comb. nov. [syn. M. aterrima (Krempelh. ex Anzi) Zahlbr.], distinguished by the ascospore size and septation, iodine reaction of the hymenial gelatin and ascus walls, and further the shape of the asci and extent of the development of the interascal filaments. The systematic position of the genus is unclear as the ascus structure shows affinities with both the Lecanorales and Dothideales. It is also uncertain whether it really should be regarded as lichenized.

Twenty-three species of Pyrenula from Latin America are treated here. Several species show characters that were not previously reported in the genus and are rare or new to lichenized fungi, viz. yellow, orange or red (KOH+ green) oil inspersion in the hymenium, yellow oil in young ascospores or longitudinal ridges on the ascospore wall. Two taxonomically significant types of over-mature spores are illustrated. The following new species are described: Pyrenula aggregataspistea Aptroot & M. Cáceres, P. aurantioinspersa Aptroot & Sipman, P. cornutispora Aptroot & M. Cáceres, P. flavoinspersa Aptroot & Sipman, P. guyanensis Sipman & Aptroot, P. infraleucotrypa Aptroot & M. Cáceres, P. inframamillana Aptroot & M. Cáceres, P. infrastroidea Aptroot & Sipman, P. maritima Sipman & Aptroot, P. mattickiana Sipman & Aptroot, P. minoides Aptroot & Sipman, P. monospora Aptroot & Sipman, P. paraminarum Aptroot & M. Cáceres, P. perfecta Aptroot & Sipman, P. plicata Sipman & Aptroot, P. rubroinspersa Aptroot & Sipman, P. rubronitidula Aptroot & M. Cáceres, P. rubrostigma Aptroot & M. Cáceres, P. tetraspora Aptroot & Sipman, P. triangularis Aptroot & Sipman, P. viridipyrgilla Aptroot & M. Cáceres. Pyrenula seminuda (Müll. Arg.) Sipman & Aptroot is a new combination.

Four new species of lichenicolous fungi are described from Bolivia: Capronia etayoi Flakus & Kukwa sp. nov. (on Dictyonema minus), Lichenosticta jurgae Kukwa & Flakus sp. nov. (on Lecanora sp.), Phaeosporobolus trypethelii Flakus & Kukwa sp. nov. (on Trypetheliumochroleucum; the host lichen new to Bolivia) and Spirographa usneae Flakus, Kukwa & Etayo sp. nov. (on Usnea sp.; also known from Ecuador).

Autecological information targeted towards rare and threatened lichen species is severely lacking. This study adopts the rare British lichen Vulpicida pinastri as a case study species and examines its ecological response to emerging threats: climate change and the recurrent loss of its primary habitat (juniper scrub). We used predictive niche modelling to examine the response of V. pinastri to a range of present-day climatic variables. A successful model was projected for a period during the 2050s based on IPCC climate change scenarios (UKCIP02 data), and threat was estimated as the proportional change in bioclimatic space. To estimate the potential range now and during the 2050s, projected bioclimatic space was masked by a habitat map equivalent to (i) the present-day distribution of juniper and (ii) theoretical juniper distribution based on existing rates of decline. Our results point to potential range loss of V. pinastri with climate warming, exacerbated by the recurrent decline in juniper habitat. This predictive modelling approach was complemented by an assessment of local stand-scale effects. At four sites in north-east Scotland we examined the occurrence and abundance of V. pinastri thalli, in response to juniper spatial distribution, and the life-stage and structure of individual shrubs. Vulpicida pinastri appeared to be dispersal limited at small-scales, and was significantly more abundant on old and degenerate juniper shrubs. Our results evidence a close relationship between management for habitat quality and effective lichen conservation. Effective conservation of V. pinastri must ensure cohorts of older and degenerate juniper shrubs are maintained at sites where the species is expected to be most resistant to long-term climate warming, i.e. in the uplands of north-east Scotland.

A detailed taxonomic survey of the saxicolous European species of Buellia based on a detailed survey and assessment of the important features of the genus is presented. These include the conidia, the anatomy of the exciple, the spore wall pigmentation, ornamentation and internal wall thickening, as well as analysis of the lichen substances. As a result, 36 saxicolous species are recognized, of which Buellia griseosquamulata and B. longispora are new taxa and B. atrocinerella and B. parvula are new combinations. Buellia coniops, B. lecideina and B. punclata are transferred to the validated genus Amandinea. A key to 43 accepted species of Buellia, Amandinea and Hafellia is included.

The new genus Silobia M. Westb. & Wedin is proposed for the Acarospora smaragdula group, which is taxonomically and nomenclaturally revised in Sweden. The proposed taxonomy results from our former molecular phylogeny, together with morphological and anatomical investigations and analysis of secondary metabolites. Seven species are recognized in Sweden in this paper: Silobia dilatata sp. nov., S. myochroa sp. nov., S. rhagadiza comb. nov., S. rufescens comb. nov., S. scabrida comb. nov., S. smaragdula comb. nov. and S. tangerina sp. nov. Acarospora alberti, A. amphibola, A. isortoquensis, A. murina and A. undata are recognized as synonyms of S. smaragdula, Acarospora verruciformis as a synonym of S. scabrida and A. scyphulifera as a synonym of S. rhagadiza. The following names are lectotypified: Acarospora amphibola, A. amphibola f. testacea, A. lesdainii, A. lesdainii var. subochracea, A. murina, A. scyphulifera f. subdiscreta, Endocarpon smaragdulum, Lecanora rhagadiza and Sagedia rufescens. Acarospora scyphulifera is neotypified. Acarospora fusca is excluded from the Swedish checklist as the specimen was found to belong to S. rufescens. A key to the species is presented.

The indirect determination of water content in lichen thalli by means of impedance measurement is described. This technique applies an alternating current between small clips placed at the margins of lichen thalli. Two zones of sensitivity were apparent in measurements with the foliose lichen Xanthoparmelia chlorochroa. Ready discrimination was provided between fully saturated thalli and thalli with standing surface water films. Similarly, this technique proved highly accurate as a measurement of thallus moisture content at water potentials of –2·5 MPa and less (between 0 and 40% water content by weight in X. chlorochroa). Resolution was lower at intermediate water contents (c. 60–100Δ water content by weight), although general trends were still clearly evident. This technique is ideally suited for unattended measurements of water potential in lichens using currently available data–logger technology and provides high resolution within the range of water potentials crucial to the control of physiological activity in lichens

Xanthoria mawsonii C. W. Dodge was found to perform well physiologically in a variety of habitats at high latitudes in continental Antarctica. The net photosynthetic rate of 7·5 μ mol CO2 kg−1 s−1 is exceptionally high for Antarctic lichens. Field and laboratory measurements proved the photosynthetic apparatus to be highly adapted to strong irradiance. The cold resistance of the photosystem II reaction centres is higher than the photosynthetic CO2 fixation process. Optimum temperature for net photosynthesis was c. 10°C. The lichen grows along water channels where it is frequently inundated and hydrated to maximum water content, although net photosynthesis is strongly depressed by super saturation. In these habitats the lichen is photosynthetically active for long periods of time. Xanthoria mawsonii also grows at sites where it depends entirely on the early spring snow melt and occasional snow fall for moisture. It has an exceptionally short reactivation phase and is able to utilize snow immediately. Recovery of activity by absorbing water vapour from air, though practically possible, seems to be of ecological importance only under snow at subzero temperatures.

The potential spatial distributions of six epiphytic lichen species were assessed in Switzerland (41 000 km2) as a function of various key climatic drivers and forest types using logistic regression models. Cetrelia cetrarioides is ‘near threatened’, Lobaria pulmonaria is ‘vulnerable’, and Graphis scripta, Hypogymnia physodes, Lecanora cadubriae, Letharia vulpina are not endangered according to the Red List assessment based on IUCN criteria. Lichen presence and absence were derived from the SwissLichens database that contains spatially explicit information on both species presence and absence.

The spatial lichen niches are predicted with R2 values between 0·5 and 0·75 and AUC values between 0·63 and 0·94. Model evaluation shows that the models perform well.

Lichenologists reviewed the spatial predictions of lichen species on the basis of their expert knowledge and concluded that parsimonious regression models may suffice for successful prediction of the potential spatial niche distributions of epiphytic lichen species.

The annual rate of lichen decomposition was measured in a mixed, cool temperate rainforest in Puyehue National Park, southern Chile. Five macrolichens, Pseudocyphellaria berberina, P. divutsa, P. glabra, P. nitida and Sticta hypochra, and bamboo leaves (Chusquaea macrostachya) were used as experimental material. Rates of decomposition are high in all lichen species and ranged from k = 0·45 to 2·79. Lichens with hopane triterpenoids {P. divulsa and P. glabra) were more resistant to decomposition. The contribution of these lichens to the nutrient economy of the rainforest ecosystem is highly significant, as they are both abundant in terms of biomass and have a rapid turnover.