An investigation of the genus Usnea, in the biodiversity hotspot of the Republic of São Tomé and Príncipe in tropical West Africa, is presented here. Fifteen species, or species aggregates, were recorded for the islands: Usnea articulata aggr., Usnea baileyi (Stirt.) Zahlbr., Usnea beckeri P. Clerc & Nadel, Usnea bicolorata Motyka, Usnea erinacea aggr., Usnea exasperata (Müll. Arg.) Motyka, Usnea firmula (Stirt.) Motyka, Usnea krogiana P. Clerc, Usnea longiciliata P. Clerc & Nadel, Usnea nodulosa Swinscow & Krog, Usnea pectinata aggr., Usnea sorediosula Motyka, Usnea submollis J. Steiner, and two undetermined species. Two species of lichen are described as new to science: U. beckeri and U. longiciliata. Both species are characterized by a dense and brittle, dark green thallus, the presence of apothecia surrounded by long cilia-like fibrils, a lack of soredia, and the presence of two unknown substances; however, whereas U. beckeri has a pendant growth form and can reach 25 cm in length, U. longiciliata is differentiated by a shrubby growth form of less than 6 cm. These two species also have different ascospore dimensions. A molecular phylogenetic analysis is presented that lends support to their description as new species. Additionally, Usnea krogiana is noted as new to continental Africa and nine Usnea species or aggregates are noted as new to the Islands of São Tomé and Príncipe in the Gulf of Guinea.

Gene expression variation can be partitioned into different components (regulatory, genetic and acclimatory effects) but for lichen-forming fungi, the relative importance of each of these effects is unclear. Here, we studied gene expression in the lichen-forming fungus Lobaria pulmonaria in response to thermal stress and parasitism by the lichenicolous fungus Plectocarpon lichenum. Our experimental procedure was to acclimate lichen thalli to 4 °C over three weeks and then expose them to 15 °C and 25 °C for 2 hours each, sampling infected and visually asymptomatic thalli at each temperature. Quantitative Real-Time PCR was utilized to quantify gene expression of six candidate genes, normalizing expression values with two reference genes. We found that two genes encoding heat shock proteins (hsp88 and hsp98), two polyketide synthase genes (rPKS1, nrPKS3) and elongation factor 1-1-α (efa) were upregulated at higher temperatures. Moreover, we observed higher expression of hsp98 at 25 °C in samples infected by P. lichenum than in uninfected samples. Finally, in partial redundancy analyses, most of the explained variation in gene expression was related to temperature treatment; genetic variation and long-term acclimatization to sites contributed far less. Hence, regulatory effects (i.e. direct adjustments of gene expression in response to the temperature change) dominated over genetic and acclimatory effects in the gene expression variability of L. pulmonaria. This study suggests that L. pulmonaria could become a valuable lichen model for studying heat shock protein responses in vivo.

Certain lichen epiphytes are restricted to old-growth forest stands with long ‘ecological continuity’, explained by i) niche specialism and their dependence on microhabitats associated with old stands including veteran or senescent trees, and/or ii) dispersal limitation with probabilities of colonization being relaxed over extended time periods. ‘Calicioid’ species are among the most important old-growth indicators, yet they reproduce sexually via small spores that appear widely dispersed at ecological scales. This suggests that they should have a high level of niche specialism compared to lichen epiphytes in general, explaining their role as old-growth indicators. However, comparisons of niche specialism are challenging, and this study uses epiphytic, corticolous calicioid species as an appropriate test case. Having measured 20 variables that constrain the lichen epiphyte niche, these were collapsed into a ‘hypervolume’ representing the sampled environmental space available for occupancy by lichens in Scotland as a study system. It was then possible to examine the occupancy of this hypervolume by individual lichens (niche breadth), with the proportion/percent occupied used to estimate a niche specialism score. Consequently, epiphyte calicioid species are confirmed to have a high degree of niche specialism compared to lichen epiphytes in general, and compared to other old-growth indicators, with their niche position directed towards drier climates including locally sheltered microhabitats associated with old-growth forest structure.

Lichen extinction occurs at rapid rates as a result of human activity, although species could potentially be rescued by conservation management based on ecophysiological knowledge. The boreal old forest cyanolichen Erioderma pedicellatum currently occurs in few sites worldwide. To protect it from extinction, it is essential to learn more about it. The last remaining good European site is a canyon with a waterfall, in a low-rainfall region of Norway. Here, a spatially restricted population of 1500–2000 thalli dominates the epiphytic vegetation of a small number of Picea abies canopies. We were able to document that 1) E. pedicellatum grew on thin branches with higher bark pH than is normal for P. abies in a canyon that provided an unusual combination of very high light, high air humidity, and cool temperatures in the growing season. However, the species did not inhabit the main waterfall spray zone. 2) Erioderma pedicellatum had a high light saturation point, high CO2 uptake at high light (≥ 600 μmol m−2 s−1) and cool temperatures (5–20 °C), and experienced strong suprasaturation depression of photosynthesis when fully hydrated. 3) It showed good tolerance of desiccation and high light; it was slightly more tolerant than the morphologically similar, but more common cyanolichen Pectenia plumbea. 4) The European population in its sunny habitat had higher water holding capacity than previously recorded in slightly shaded rainforest populations in Newfoundland, consistent with acclimation to compensate for high evaporative demands. Understanding the ecological niche and responses to critical environmental factors is essential for action plans to avoid extinction of E. pedicellatum. Methods used in this study could also be applicable for ecological understanding of other threatened lichen species.

The epiphytic lichen species richness and community composition was compared for 600 living trees distributed within the interior of 60 Scots pine and Norway spruce monoculture stands in southern Sweden. A higher species richness, and more unique species, was found on trees of Scots pine than of Norway spruce, and distinctive communities were associated with the two tree species. Lichen species composition also shifted between the 30-, 55- and 80-year-old stands, although there was no significant difference in species richness between the different age classes. Tree species and age of the stand explained most of the variation in community composition (41%), with additional variance explained by lichen proximity to the ground (6%) and aspect (1%) (northern/southern side of trunk). Scots pine and Norway spruce share many attributes, such as both being conifers with acidic bark properties and having a similar geographical distribution in Fennoscandia. However, our study showed that species richness and community composition can nevertheless diverge in stands dominated by these two tree species. Since the occurrence of red-listed species was low in these stands, we suggest that 80-year rotations are not long enough for the occurrence of the many rare and specialized lichen species that require old forest structures and long forest continuity in this region.

This study investigated the molecular, chemical and morphological variation in the Usnea pectinata aggregate using 42 specimens, 22 from Tanzania and 20 from São Tomé and Príncipe. A total of 31 sequences (13 ITS, 13 nuLSU and 5 RPB1) were generated. The results are presented in two phylogenies: first a three-markers ‘backbone’ phylogeny for the U. pectinata aggregate, where six distinct, strongly supported subclades indicate considerable genetic variation in the dataset; and second, an ITS phylogeny with 47 terminals along with a mapping of morphological and chemistry data. Several well-supported monophyletic clades were recovered in both phylogenies and these may well represent separate species in the complex referred to here as the U. pectinata aggregate. Three morphotypes characterized by axis pigmentation and four by branch shape were noted. Six chemotypes were observed.

Of the c. 900 lichen species known from Kenya, 178 belong to the parmelioid clade. Several of these parmelioid taxa require further revisionary studies. An identification key to the species of the parmelioid clade, based on updated nomenclature, is produced to support the practical work in collecting and selecting certain parmelioid lichens for further research. A new combination Parmotrema nyasense (C. W. Dodge) R. S. Egan comb. nov. in Egan et al., Bibliotheca Lichenologica 110, 383 (2016) is published here by R. S. Egan.

Photosynthetic organisms have evolved a great variety of mechanisms to optimize their use of sunlight. Some of the clearest examples of adaptations can be seen by comparing photosynthesis in different species and in different individuals of the same species that grow under high and low light levels. While the adaptations of sun and shade higher plants have been relatively well studied, much less information is available on the photobionts of lichenized Ascomycetes. An important adaptation that can protect photosynthetic organisms from the potentially harmful effects of excess light is non-photochemical quenching (NPQ); NPQ can dissipate unused light energy as heat. Here we used chlorophyll fluorescence to compare the induction and relaxation of NPQ and the induction of electron transport (rETR) in collections of the same lichen species from exposed and from more shaded locations. All species have trebouxioid photobionts and normally grow in more exposed microhabitats but can also be readily collected from more shaded locations. Shade forms display generally higher NPQ, presumably to protect lichens from occasional rapid increases in light that occur during sunflecks. Furthermore, the NPQ of shade forms relaxes quickly when light levels are reduced, presumably to ensure efficient photosynthesis after a sunfleck has passed. The maximal relative electron transport rate is lower in shade than sun collections, probably reflecting a downregulation of photosynthetic capacity to reduce energy costs. We also compared collections of pale and melanized thalli from three species of shade lichens with Symbiochloris as their photobiont. Interestingly, NPQ in melanized thalli from slightly more exposed microhabitats induced and relaxed in a way that resembled shade rather than sun forms of the trebouxioid lichens. This might suggest that in some locations melanization induced during a temporary period of high light may be excessive and could potentially reduce photosynthesis later in the growing season. Taken together, the results suggest that lichen photobionts can flexibly adjust the amount and type of NPQ, and their levels of rETR in response to light availability.

In this study, we sampled L. pulmonaria thalli from Mt Kilimanjaro and Mt Meru, Tanzania. Across all sampled tree species, a range of 1–35 thalli of L. pulmonaria were counted per trunk (up to 5 m above ground level), with sampling distributed across 13 (c. 1 ha) plots located in the sub-alpine to montane forest altitudinal gradients of Mt Kilimanjaro and Mt Meru. Descriptive analyses were performed to determine the association of L. pulmonaria with particular host trees among the study sites and regions, and linear mixed effects models (LMM) were used to explore relationships with tree-level variables. The analyses showed that most thalli of L. pulmonaria were unevenly distributed among the tree species in the montane and sub-alpine forests of Mt Kilimanjaro and Mt Meru. Host tree characteristics such as trunk circumference, height on trunk, bark texture and trunk shape appeared to have an effect on the local population size of L. pulmonaria and the frequency of occurrence. Also, the results indicated an effect of trunk circumference and tree bark on the development of L. pulmonaria thallus size among the study sites. Furthermore, host tree species, for example, Hypericum revolutum and Rapenea melanophloeos were important habitats for L. pulmonaria on both mountains, whereas Ilex mitis, Bersama abyssinica and Hagenia abyssinica were important only on one mountain. The wider literature on L. pulmonaria ecology is also reviewed and it is therefore recommended that for successful conservation of the threatened L. pulmonaria in tropical montane forests, strategies should consider the type of the forests, together with the host tree species and their size.