A synopsis of the 10 genera and 34 species of Pilotrichaceae recorded from the state of Rio de Janeiro, Brazil is provided, presenting a key to the genera and species, synonyms, comments, distribution and altitudinal range and illustrations. Recently, the authors excluded poorly known taxa and doubtful records of the family from Rio de Janeiro, reducing by 39% the total taxa number of Pilotrichaceae for the state. These taxa are given in a list at the end of the present work.

Desiccation-tolerance, the ability to revive from the air-dried state, is found in prokaryotes, algae and bryophytes, and occasionally in pteridophytes, but is very rare in the vegetative tissues of angiosperms or in animal tissues. However, the vast majority of lichens are desiccation-tolerant. Under natural conditions, the life of most lichens is characterized by rapidly changing water contents, and correspondingly rapidly changing physiological activity such as respiration and photosynthesis. Taken to the extreme, some lichens can revive after being desiccated under controlled laboratory conditions for many months. As a result of their desiccation-tolerance, lichens are extremophiles and can live in places no higher plant can. They may be the predominant life-form in ecosystems characterized by severe environmental stresses such as Arctic, Antarctic and alpine regions, as well as deserts. This review critically assesses our current knowledge about desiccation-tolerance in lichens, concentrating on mechanisms that protect from desiccation-induced damage. Evidence available from other desiccation-tolerant life-forms suggests that desiccation-tolerance is a multifaceted trait involving a suite of interacting mechanisms. The majority of recent studies on mechanisms of lichen desiccation-tolerance have focused on the scavenging of reactive oxygen species, which therefore forms a major part of this review. It is argued that effective control of reactive oxygen species and mutual up-regulation of protective mechanisms was critically important for the evolution of lichens, facilitating the transition from free-living fungi and green algae or cyanobacteria to the lichenized state. Recently developed tools of molecular biology, particularly from the -omics disciplines, have only just started to be applied to lichens. There remain many unsolved questions as to how lichens survive desiccation and the authors hope to encourage more scientists to investigate this intriguing phenomenon.

Little is known about species diversity and genetic structure of populations of lichens and bryophytes in the Sandilands Provincial Forest in Manitoba. This study investigated the current species diversity of lichens and bryophytes in the area. It also examined the population structure and gene flow in the lichen (Cladonia arbuscula) with the highest cover and second most frequent occurrence, and bryophyte (Pleurozium schreberi) with the highest frequency and percent ground cover. Analysis of Molecular Variance (AMOVA) of the presence and absence of group I introns in the fungal small subunit (SSU) nuclear ribosomal DNA (rDNA) and Restriction Fragment Length Polymorphisms (RFLP) of the algal Internal Transcribed Spacer (ITS) rDNA suggests that low levels of gene flow were occurring in the fungus while a single algal genotype was maintaining the lichen association. Similarly, Interspersed Simple Sequence Repeat (ISSR) markers of the bryophyte suggested low levels of gene flow. The examination of variation in both lichen symbionts and a bryophyte, dominant within the same habitat, is a novel aspect of this study. Both these widespread species, dominating the understory in mature jack pine forests, exhibited low levels of sexual reproduction.

Macroclichen and bryophyte species diversity, abundance, biomass and nitrogen stocks were compared between arboreal and terrestrial habitats in old-growth sub-boreal spruce forests in central British Columbia, Canada on the two most common soil types in the area, fine- and coarse-textured soils. A total of 118 macrolichen and bryophyte species were identified, including 71 species of macrolichens (44 arboreal and 43 terrestrial) and 47 species of bryophytes, of which only one moss (Orthotrichum sp.) was arboreal. Macrolichen functional groups varied in both diversity and abundance between arboreal and terrestrial communities. Cyanolichens were common in both arboreal and terrestrial habitats, but were much more abundant arboreally than terrestrially. This epiphytic biomass was largely attributed to the tripartite cyanolichen species, Lobaria pulmonaria, while the most common terrestrial macrolichens were bipartite Peltigera cyanolichen species. From a biomass perspective, the epiphyte community was almost entirely lichens while the terrestrial community was predominantly bryophytes. Terrestrial and arboreal macrolichens and bryophytes made a relatively small contribution to total forest above-ground biomass (0.5–1.4% or 1698–3339 kg ha⁻¹), however, a comparison between macrolichen and bryophyte biomass and tree foliar biomass showed lichens and bryophytes to be equivalent to 11.7–20.5% of tree foliar biomass. Macrolichens made a proportionately large contribution when compared to forest foliar nitrogen and contained 6.4–8.1% of forest foliar nitrogen. Nitrogen contents varied greatly between functional groups, from a maximum of 3.98% N in terrestrial bipartite cyanolichens to a minimum of 0.37% N in Alectoria hair lichens. In total, terrestrial and arboreal lichens and bryophytes represented 20–39 kg N ha⁻¹ in this old-growth sub-boreal spruce ecosystem.

The relationship between lichen species richness and forest age was explored in southwestern Nova Scotia by examining the epiphytic lichens in 51 conifer-dominated forest stands with no evidence of harvesting. The stand ages were determined by tree cores and ranged from 52 to 292 years. One hundred and thirty-five lichen species in 61 genera were identified, of which 25 species are new records for Nova Scotia, and two appear to be species new to science. Using the Nova Scotia Department of Natural Resources' age thresholds, 12 of the 135 lichen species were found exclusively in “early old-growth” and 16 were found only in “advanced old-growth” forest stands. These forests have a diverse lichen flora including green-alga containing macrolichens, a spectrum of crustose taxa and eight genera and 21 species of cyanolichens, the latter being found mainly on deciduous trees.

Data on the identified lichen species were used, with the help of two existing indices of ecological continuity, to calculate a value for each of the 51 forest stands assessed. The values should represent an age category (i.e., the higher the value the older the forest stand). The values calculated, however, using either of these indices, were not high enough to identify any of the stands as “old-growth.” In contrast, the stand ages determined using tree cores, showed that some stands were old enough to be defined as “old-growth.” The failure of index 1 to identify any stands as old-growth was likely due to regional ecological variations, suggesting that a new suite of lichens needs to be developed for southwestern Nova Scotia. The problems with index 2, which used calicioid lichens as a predictor of old-growth, appeared to be that insufficient data were collected on these easily overlooked taxa.

“Critical load” and “critical level” (the deposition or concentration, respectively, of atmospheric pollutants above which negative ecosystem effects occur) concepts are reviewed for the North American lichenological community with the objective of stimulating interest and participation in this emerging field of research. We focus on how regional, lichen-based critical loads for nitrogen-, sulfur- and metal-containing pollutants could be developed for various terrestrial ecosystems in the U.S. utilizing existing data. Specifically we provide examples of how lichen community and element concentration responses to air pollution can be linked with measured or modeled estimates of depositional air pollutants. Preliminary critical loads of 0.26–0.33 kg ha⁻¹ yr⁻¹ for deposition of inorganic N in fine particulates and critical levels of 0.044–0.055 mg L⁻¹ for wet deposition of ammonium ions are suggested for coniferous forests of western Oregon and Washington. These correspond to initial declines in presence and abundance of sensitive species and a % N concentration of 0.55–0.61 in Platismatia glauca. Indicator species distribution and abundance as well as physiological, morphological, growth or reproduction responses can also be used to set critical loads. Further research needs are identified.

Erioderma pedicellatum and fifteen other rare cyanolichens in Atlantic coastal forests in Nova Scotia are at risk from human activities. A heuristic expert habitat model was developed for use in a GIS to help identify polygons with habitat for these at-risk cyanolichens. Of 13,852 polygons identified by the model, 183 were surveyed for rare cyanolichens. One hundred and one of surveyed polygons had at least one species of rare cyanolichen. Habitat data were collected from twenty sites which had Erioderma pedicellatum. The habitat model can be used to identify important lichen areas for conservation and research.

The crustose Roccellaceae, excluding Opegrapha, on the Galapagos Islands were investigated. In total, 24 species were identified, most of which are new records not only for the archipelago, but also for Ecuador. These include Schismatomma spierii, which is described as new to science. Lecanographa laingiana is reported for the first time from the New World and Bactrospora denticulata, Dirina catalinariae, Lecanographa hypothallina, L. illecebrosula, Sclerophyton murex and S. vertex are first records from the Southern Hemisphere. Previous records of Roccellina from the Galapagos are regarded as erroneous. A key to the species is provided.

A bryological survey in southeastern Brazil revealed a new species, Cylindrocolea brasiliensis (Cephaloziellaceae). The principal distinguishing character of this species is the dentate margin of the ventral leaf-lobe. The new species is described, illustrated and discussed, and an updated key to the Brazilian species of Cylindrocolea is provided.

A new Orthotrichum species, O. norrisii, is described from California. The new taxon is recognized by a unique combination of sporophytic characters: capsule narrowly cylindrical and not contracted below mouth when dry, exothecial bands narrow and formed by 2(–3) cell rows, peristome with eight pairs of exostome teeth and eight endostome segments, stomata cryptopore and located in the lower part of the urn, lid plane and rostrate and vaginula hairy. Widely distributed throughout California, the new taxon has been overlooked and confused with O. tenellum.

Syntrichia sucrosa is described and illustrated as a new species from California. It is characterized by 1–4, pedicellate, bifurcate or stellate-branched papillae per cell, upper laminal cells 8–11 µm in width, costa with hydroids and 2–4 layers of stereid cells, and margins recurved in the basal ¾ of the ± lingulate leaf. A key to the mosses with pedicellate papillae in the Northern Hemisphere is presented.