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Lichens are presently regarded as stable biotopes, small ecosystems providing a safe haven for the development of a diverse and numerous microbiome. In this study, we conducted a functional diversity assessment of the microbial community residing on the surface and within the thalli of Leptogium puberulum, a eurytopic cyanolichen endemic to Antarctica, employing the widely used Biolog EcoPlates which test the catabolism of 31 carbon compounds in a colorimetric respiration assay. Lichen thalli occupying moraine ridges of differing age within a proglacial chronosequence, as well as those growing in sites of contrasting nutrient concentrations, were procured from the diverse landscape of the western shore of Admiralty Bay in Maritime Antarctica. The L. puberulum bacterial community catabolized photobiont- (glucose-containing carbohydrates) and mycobiont-specific carbon compounds (d-Mannitol). The bacteria also had the ability to process degradation products of lichen thalli components (d-cellobiose and N-acetyl-d-glucosamine). Lichen thalli growth site characteristics had an impact on metabolic diversity and respiration intensity of the bacterial communities. While high nutrient contents in lichen specimens from “young” proglacial locations and in those from nitrogen enriched sites stimulated bacterial catabolic activity, in old proglacial locations and in nutrient-lacking sites, a metabolic activity restriction was apparent, presumably due to lichen-specific microbial control mechanisms.

The focus of community ecology has shifted from the description of taxonomic composition towards an understanding of community assembly based on species’ ‘functional traits’. The functional trait approach is well developed for vascular plants, utilising variability of continuous phenotypic characters that affect ecological fitness, such as specific leaf area, tissue nitrogen concentration or seed mass, to explain community structure. In contrast, community assembly studies for poikilohydric cryptogamic plants and fungi, such as lichens, remain focused on broad categorical traits such as growth form difference: fruticose, foliose or crustose. This study examined intra- and interspecific variability for two highly promising continuous phenotypic measurements that affect lichen physiology and ecological fitness: water-holding capacity (WHC) and specific thallus mass (STM). Values for WHC and STM were compared within and among species, and within and among key macrolichen growth forms (fruticose and green-algal and cyanolichen foliose species), asking whether these widely used categories adequately differentiate the continuous variables (WHC and STM). We show large intra- and interspecific variability that does not map satisfactorily onto growth form categories, and on this basis provide recommendations and caveats in the future use of lichen functional traits.

Chlorophyll content in lichens is routinely used as an accurate indicator of lichen vigor, interspecific differences, and the effect of site-related environmental parameters. Traditional methods of chlorophyll extraction are destructive, time-consuming, expensive, and inoperable, especially when measuring large quantities of chlorophyll. However, non-destructive methods of measurement using portable chlorophyll meters are rarely used for lichens. Considering the characteristics of lichens such as rough blade surface and absence of chlorophyll b in cyanolichens, we compared the non-destructive methods with traditional methods and evaluated their applicability in studying lichen pigment content. Two instruments, SPAD-502 and CCM-300, were used to measure the pigment content of seven foliose lichen species. These pigment readings were compared with those determined using the dimethyl sulphoxide (DMSO) extraction method. Significant correlations were observed between SPAD/CCM values and pigments (chlorophyll and total carotenoids) extracted from chlorolichens, especially species with a smooth surface. The CCM-300 was more accurate in detecting the pigment content of foliose chlorolichens. However, both instruments showed certain limitations in the determination of pigment content in cyanolichens, especially gelatinous species. For example, CCM-300 often failed to give specific values for some cyanolichen samples, and both instruments showed low measurement accuracy for cyanolichens. Based on the high correlation observed between chlorophyll meter readings and pigments extracted from chlorolichens, equations obtained in this study enabled accurate prediction of pigment content in these lichens.

Lichen thalli are formed through the symbiotic association of a filamentous fungus and photosynthetic green alga and/or cyanobacterium. Recent studies have revealed lichens also host highly diverse communities of secondary fungal and bacterial symbionts, yet few studies have examined the viral component within these complex symbioses. Here, we describe viral biodiversity and functions in cyanolichens collected from across North America and Europe. As current machine-learning viral-detection tools are not trained on complex eukaryotic metagenomes, we first developed efficient methods to remove eukaryotic reads prior to viral detection and a custom pipeline to validate viral contigs predicted with three machine-learning methods. Our resulting high-quality viral data illustrate that every cyanolichen thallus contains diverse viruses that are distinct from viruses in other terrestrial ecosystems. In addition to cyanobacteria, predicted viral hosts include other lichen-associated bacterial lineages and algae, although a large fraction of viral contigs had no host prediction. Functional annotation of cyanolichen viral sequences predicts numerous viral-encoded auxiliary metabolic genes (AMGs) involved in amino acid, nucleotide, and carbohydrate metabolism, including AMGs for secondary metabolism (antibiotics and antimicrobials) and fatty acid biosynthesis. Overall, the diversity of cyanolichen AMGs suggests that viruses may alter microbial interactions within these complex symbiotic assemblages.

International audience; While depsidones, depsides or dibenzofuran-like compounds dominate the chemical composition of lichens, the cyanolichen Nephroma laevigatum affords a diversity of quinoid pigments represented by chlorinated anthraquinones derived from emodin and new bianthrones resulting from the homo- or heterodimerization of monomers. Bianthrones were pointed out from the dichloromethane extract by MS/MS-based molecular networking, then isolated and characterized on the basis of extensive spectroscopic analyzes and GIAO NMR shift calculation followed by CP3 analyzes.

Recent studies have uncovered remarkable diversity in Dictyonema s.lat. basidiolichens, here recognized as subtribe Dictyonemateae. This group includes five genera and 148 species, but hundreds more await description. The photobionts of these lichens belong to Rhizonema, a recently resurrected cyanobacterial genus known by a single species. To further investigate photobiont diversity within Dictyonemateae, we generated 765 new cyanobacterial sequences from 635 specimens collected from 18 countries. The ITS barcoding locus supported the recognition of 200 mycobiont (fungal) species among these samples, but the photobiont diversity was comparatively low. Our analyses revealed three main divisions of Rhizonema, with two repeatedly recovered as monophyletic (proposed as new species), and the third mostly paraphyletic. The paraphyletic lineage corresponds to R. interruptum and partnered with mycobionts from all five genera in Dictyonemateae. There was no evidence of photobiont-mycobiont co-speciation, but one of the monophyletic lineages of Rhizonema appears to partner predominantly with one of the two major clades of Cora (mycobiont) with samples collected largely from the northern Andes. Molecular clock estimations indicate the Rhizonema species are much older than the fungal species in the Dictyonemateae, suggesting that these basidiolichens obtained their photobionts from older ascolichen lineages and the photobiont variation in extant lineages of Dictyonemateae is the result of multiple photobiont switches. These results support the hypothesis of lichens representing "fungal farmers," in which diverse mycobiont lineages associate with a substantially lower diversity of photobionts by sharing those photobionts best suited for the lichen symbiosis among multiple and often unrelated mycobiont lineages.

Biocrusts are the living skin of drylands, comprising diverse microbial communities that are essential to desert ecosystems. Despite there being extensive knowledge on biocrust ecosystem functions and lichen and moss biodiversity, little is known about factors structuring diversity among their microbial communities. We used amplicon-based metabarcode sequencing to survey microbial communities from biocrust surface and subsurface soils at four sites located within the Mojave Desert. Five biocrust types were examined: Light-algal/Cyanobacteria, Cyanolichen, Green-algal lichen, Smooth-moss and Rough-moss crust types. Microbial diversity in biocrusts was structured by several characteristics: (i) central versus southern Mojave sites displayed different community signatures, (ii) indicator taxa of plant-associated fungi (plant pathogens and wood saprotrophs) were identified at each site, (iii) surface and subsurface microbial communities were distinct and (iv) crust types had distinct indicator taxa. Network analysis ranked bacteria–bacteria interactions as the most connected of all within-domain and cross-domain interaction networks in biocrust surface samples. Actinobacteria, Proteobacteria, Cyanobacteria and Ascomycota functioned as hubs among all phyla. The bacteria Pseudonocardia sp. (Pseudonocardiales, Actinobacteria) and fungus Alternaria sp. (Pleosporales, Ascomycota) were the most connected had the highest node degree. Our findings provide crucial insights for dryland microbial community ecology, conservation and sustainable management.

Fuscopannaria leucostictais a rare and understudied cyanolichen with an interesting and unusual distribution in tertiary relict hotspots worldwide. There is a relatively large population in eastern North America, where it occurs mostly throughout the Appalachian Mountains and reaches its northernmost extent in New Brunswick and Nova Scotia, Canada. The ability to detect this species, and thus determine its habitat requirements, is critical for understanding how it might be affected by human-induced environmental degradation. Maximum entropy modelling with MaxEnt was used to predict the distribution of suitable habitat for this species in Nova Scotia using 62 presence locations, 1405 pseudo-absence locations and four environmental covariates: depth to water table (a proxy for relative soil moisture), distance to the coast and mean annual temperature and precipitation. Our predictive maps identify important habitat features and areas of high suitability in Nova Scotia with an area under the curve value of 0·85. The predicted distribution of this lichen was most affected by temperature. This study elucidates locations as well as species-habitat relationships forF. leucosticta,providing land managers with baseline data that can aid in the discovery of additional populations and provide a better understanding of its ecological requirements which will support the development of sound conservation strategies for this rare lichen.

Quantitative parameters of cenopopulations of Lobaria pulmonaria, an endangered cyanolichen, have been studied in spruce phytocenoses of Karelia recovering after disturbance through the successional stage of aspen stands for a period ranging from 80 to 450 years. The results show that, as the time since disturbance increases, the total number of L. pulmonaria thalli and the number of colonized substrate units increase as well, with no stabilization of these parameters being observed in the series of communities studied. The total area of thalli in the phytocenoses is restored within approximately 200 years after the last disturbance. In old-growth forests (>400 years), L. pulmonaria thalli colonize a broad spectrum of tree species in different life states, including lower branches of young spruce trees. Even if they serve as temporary substrates, this can markedly strengthen the potential of the species for further expansion within the community in case of shortage in the main phorophyte (aspen). Thus, the proportion of regressive populations decreases, while that of colonizing populations increases, which is indicative of successful reproduction of the species.

Biological soil crusts (BSCs) have important ecological functions in arid and semiarid lands, but they remain poorly understood in terms of the changes in microbial communities during BSC succession under in situ field conditions. Here, 454 pyrosequencing was used to assess the microbial community composition of four BSC types in the Tengger Desert of China: alga, lichen (cyanolichen and green alga-lichen), and moss crusts, representing early, middle, and final successional stages of BSCs, respectively. The results showed the highest diversity of microbial communities inhabiting lichen crusts, whereas the lowest diversity was observed in moss crusts. Five phyla, Proteobacteria, Actinobacteria, Cyanobacteria, Bacteroidetes, and Acidobacteria, accounted for about 72% to 87% of total prokaryotic sequences in different BSCs. The most abundant eukaryotic microorganism was Ascomycota, accounting for 47% to 93% of the total eukaryotic sequences. Along the succession of BSCs, the abundance of photoautotrophic Cyanobacteria, Chlorophyta, and Bacillariophyta declined, and that of heterotrophic microorganisms such as bacteria and fungi increased. Statistical analysis showed clear divergency of microbial taxa at the class level among the different successional stages of BSCs. The clustering results at class level showed that the moss crusts were the farthest from the rest in prokaryotic composition; the alga crusts were the most different in terms of eukaryotic microorganisms and the two kinds of lichen crusts were relatively closer in both compositions. Ordination analysis showed that the main variations of community structure among BSCs could be explained best by the abundance of Cyanobacteria and Ascomycota and by physiochemical properties of BSCs, including mechanical composition, moisture, and electrical conductivity. In conclusion, our results indicate that Cyanobacteria and Ascomycota likely play an important role in the evolution of BSC structure and functions and highlight the importance of environmental factors in shaping microbial community structures of BSCs in the Tengger Desert of China.

Nitrogen (N) fixed by epiphytic cyanolichens (i.e. lichens that contain cyanobacterial symbionts) is thought to be the most important resource of this nutrient in some natural forest ecosystems. Although a great deal of work has been carried out to evaluate the biomass of this group as well as its contribution to ecosystem N budgets, empirical studies are needed to confirm the N input responses by cyanolichens under climate change conditions (dry-hot stress) as well as to determine the factors that control this process. We simulated climate change conditions by transplanting Lobaria retigera, a common cyanolichen in the area, to lower elevations, and measured nitrogenase activity in response to warmer and drier conditions. In addition, we conducted a series of laboratory and greenhouse experiments to determine the dominant factors influencing nitrogenase activity in this species. The results of this study show that mean annual nitrogenase activity at the higher site was 1.5 and 2.4 times that at the simulated warmer and drier (middle and lower) sites, respectively. Combining laboratory experimental conclusions, we show that thallus water content is a key factor determining the nitrogenase activity of L. retigera in early transplantation while insufficient carbon storage resulting from a combination of warming and desiccation was likely responsible for reducing nitrogenase activity in later months of the transplant experiment. The results of this study imply that the negative impact of climate change (dry-hot stress) on ecosystems not only impacts the distribution and growth of species, but also nutrient circles and budgets.

Premise of research. Recent high-throughput molecular analyses indicate that lichen consortia include bacterial communities, but these are not always characterized at the generic taxonomic level, a...

During lichenological explorations of tropical montane forests in Kenya, a remarkable new lichenicolous fungus was repeatedly found growing on thalli of the epiphytic tripartite cyanolichen Crocodia cf. clathrata. Molecular phylogenetic analyses placed the fungus within Gomphillaceae (Ostropales, Lecanoromycetes), a family mainly of lichen-symbiotic species in the tropics. The anatomical features (unitunicate, non-amyloid asci and simple, septate paraphyses) as well as the hemiangiocarpic ascoma development confirm its taxonomic affinity. DNA sequence data showed the closest relationship was with Gyalidea fritzei, followed by Corticifraga peltigerae. A monotypic genus, Taitaia, is introduced to incorporate a single species, T. aurea. The new fungus is characterized by aggregated ascomata with yellow margins and salmon red discs developing from a single base.

Plants and biological soil crusts (biocrusts) are the key producers in drylands, but biocrusts seldom show net CO2 uptake. I hypothesized that biocrusts could augment CO2 fixation by incorporating plant-derived carbon. I collected biocrusts located at the base of Gutierrezia sarothrae (C3 forb), Bouteloua gracilis (C4 grass), and from bare interspaces between plants, and from a mesocosm experiment with live B. gracilis or dead B. gracilis roots. To trace carbon sources, I determined 13C values of the biocrust community, isolated cyanobacteria and lichen, and plant leaves because the photosynthetic pathway distinguishes the tissue 13C values. Biocrust communities and washed cyanobacteria and cyanolichen in G. sarothrae microsites were depleted by ~2‰ relative to other locations. Biocrust δ13C did not differ between the interspace and live or dead B. gracilis. Potential mechanisms for the trend in biocrust δ13C adjacent to C3 plants include differences in microsite conditions, biocrust communities, use of respired CO2 in the soil matrix for photosynthesis, or mixotrophic use of plant photosynthates. Further investigation of this observation may improve understanding of the degree to which the activities of dryland primary producers are coupled.

Lichens are frequently used as indicators of air-borne depositions, yet the differential effect of different mineral nutrients on lichen growth is still poorly understood. Here we quantify relative lichen growth rates (RGR) in representatives of three functional groups (chloro-, cephalo-, cyanolichens; Xanthoria parietina, Lobaria pulmonaria, Lobarina scrobiculata, respectively) placed in growth cabinets and subjected to eight fertilization regimes, i.e. four concentrations of NH4NO3 with and without the addition of other essential nutrients. After the experimental period of 14 days, we were able to document: (1) most N in the sprayed solutions that could fill the lichen's water holding capacity (WHC) was taken up, except for lower uptake in the cyanolichen at high N irrigation; (2) an increase in chlorophyll a (Chl a – a proxy of photosynthetic capacity) in the chlorolichen with increasing N irrigation; (3) a strong corresponding decline in Chl a in the cyanolichen; (4) unchanged Chl a in the cephalolichen; and (5) a decline in RGR in all species with increasing N irrigation. Addition of other essential nutrients significantly boosted RGR in all species, suggesting that N was not the most limiting element. We conclude that (1) short-term growth experiments can characterize lichens’ fitness in response to mineral nutrient deposition, and that (2) WHC contributes to lichens’ capacity to capture mineral nutrients from wet depositions.

The taxonomic delimitation and generic placement of Santessoniella crossophylla (Old Gray Crosslobes), a cyanolichen endemic to eastern North America, are revisited based on newly generated nrITS and mtSSU sequences. A population from Nova Scotia whose identification as S. crossophylla has been questioned is confirmed as belonging to the species. The monospecific genus Rockefellera is introduced to accommodate lichens ascribable to S. crossophylla in light of molecular results herein presented. The new name honors the Rockefeller family for their century-long support of North American conservation efforts, particularly with respect to national parks.

Forest managers in many parts of the world are charged with protecting rare lichen species, including species growing near their range limits. Rare lichens may be particularly vulnerable to effects of climate change, and conserving lichen diversity necessitates understanding factors that limit species distributions. Habitat suitability envelopes for lichens are shifting as the climate changes, but it is unclear whether and how local (e.g., within-tree) lichen species distributions will shift. Conserving lichen biodiversity also requires effective field surveys to detect and monitor rare lichen populations. However, the reliability of rare lichen survey methods currently used across global forest lands is rarely tested. In this study, we quantify the canopy distribution of an epiphytic old-growth forest cyanolichen near its southern range limit and test whether ground surveys reliably detect canopy populations. Near its southern range limit, Lobaria oregana was most abundant in two distinct zones within tree crowns: on branches of large trees in the mid-crown, and on boles of small trees near ground level. The abundance of this species near ground level suggests that lichens may benefit from cooler, wetter microclimates near the equatorial edges of their ranges. Maintaining these microclimate habitats may be a key to long-term viability of rear edge lichen populations. Targeted ground surveys reliably detected L. oregana in litterfall underneath trees where it was abundant in the crowns. However, ground surveys did not reliably detect the lichen underneath trees when it occurred in the crowns in low abundance. Our results suggest that ground surveys are useful for characterizing abundant lichen species, but that canopy surveys (e.g., tree climbing) may be needed to reliably detect lichens when they occur at low abundance.

Background In this study, we investigate species limits in the cyanobacterial lichen genus Rostania (Collemataceae, Peltigerales, Lecanoromycetes). Four molecular markers (mtSSU rDNA, β-tubulin, MCM7, RPB2) were sequenced and analysed with two coalescent-based species delimitation methods: the Generalized Mixed Yule Coalescent model (GMYC) and a Bayesian species delimitation method (BPP) using a multispecies coalescence model (MSC), the latter with or without an a priori defined guide tree. Results Species delimitation analyses indicate the presence of eight strongly supported candidate species. Conclusive correlation between morphological/ecological characters and genetic delimitation could be found for six of these. Of the two additional candidate species, one is represented by a single sterile specimen and the other currently lacks morphological or ecological supporting evidence. Conclusions We conclude that Rostania includes a minimum of six species: R. ceranisca, R. multipunctata, R. occultata 1, R. occultata 2, R. occultata 3, and R. occultata 4,5,6. Three distinct Nostoc morphotypes occur in Rostania, and there is substantial correlation between these morphotypes and Rostania thallus morphology.

Background and AimsIn order to re-establish lichen symbiosis, fungal spores must first germinate and then associate with a compatible photobiont. To detect possible establishment limitations in a sexually reproducing cyanolichen species, we studied ascospore germination, photobiont growth and photobiont association patterns in Pectenia plumbea.MethodsGermination tests were made with ascospores from 500 apothecia under different treatments, and photobiont growth was analysed in 192 isolates obtained from 24 thalli. We determined the genotype identity [tRNALeu (UAA) intron] of the Nostoc cyanobionts from 30 P. plumbea thalli from one population. We also sequenced cyanobionts of 41 specimens of other cyanolichen species and 58 Nostoc free-living colonies cultured from the bark substrate.Key ResultsNot a single fungal ascospore germinated and none of the photobiont isolates produced motile hormogonia. Genetic analyses revealed that P. plumbea shares Nostoc genotypes with two other cyanolichen species of the same habitat, but these photobionts were hardly present in the bark substrate.ConclusionsDue to the inability of both symbionts to thrive independently, the establishment of P. plumbea seems to depend on Dendriscocaulon umhausense, the only cyanolichen species in the same habitat that reproduces asexually and acts as a source of appropriate cyanobionts. This provides support to the hypothesis about facilitation among lichens.

We studied the genotype diversity of cyanobacterial symbionts in the predominately terricolous cyanolichen genus Peltigera (Peltigerales, Lecanoromycetes) in Estonia. Our sampling comprised 252 lichen specimens collected in grasslands and forests from different parts of the country, which represented all common Peltigera taxa in the region. The cyanobacteria were grouped according to their tRNA(Leu) (UAA) intron sequences, and mycobiont identities were confirmed using fungal ITS sequences. The studied Peltigera species associated with 34 different "Peltigera-type" Nostoc trnL genotypes. Some Peltigera species associated with one or a few trnL genotypes while others associated with a much wider range of genotypes. Mycobiont identity was the primary factor that determined the presence of the specific Nostoc genotype within the studied Peltigera thalli. However, the species-specific patterns of cyanobiont selectivity did not always reflect phylogenetic relationships among the studied fungal species but correlated instead with habitat preferences. Several taxa from different sections of the genus Peltigera were associated with the same Nostoc genotype or with genotypes in the same habitat, indicating the presence of functional guild structure in the photobiont community. Some Nostoc trnL genotypes were only found in the Peltigera species of moist and mesic forest environments, while another set of Nostoc genotypes was typically found in the Peltigera species of xeric habitats. Some Nostoc trnL genotypes were only found in the Peltigera taxa that are common on alvars and may have specialized to living in this unusual and threatened habitat type. (C) 2018 Elsevier Ltd and British Mycological Society. All rights reserved.

Organisms have evolved different cellular mechanisms to deal with environmental stress, primarily through complex molecular mechanisms including protein refolding and DNA repair. As mutualistic symbioses, lichens offer the possibility of analyzing molecular stress responses in a particularly tight interspecific relationship. We study the widespread cyanolichen Peltigera membranacea, a key player in carbon and nitrogen cycling in terrestrial ecosystems at northern latitudes. We ask whether increased temperature is reflected in mRNA levels of selected damage control genes, and do the response patterns show geographical associations? Using real-time PCR quantification of 38 transcripts, differential expression was demonstrated for nine cyanobacterial and nine fungal stress response genes (plus the fungal symbiosis-related lec2 gene) when the temperature was increased from 5 °C to 15 °C and 25 °C. Principle component analysis (PCA) revealed two gene groups with different response patterns. Whereas a set of cyanobacterial DNA repair genes and the fungal lec2 (PC1 group) showed an expression drop at 15 °C vs. 5 °C, most fungal candidates (PC2 group) showed increased expression at 25 °C vs. 5 °C. PC1 responses also correlated with elevation. The correlated downregulation of lec2 and cyanobacterial DNA repair genes suggests a possible interplay between the symbionts warranting further studies.

Erioderma pedicellatum, an enigmatic boreal cyanolichen epiphyte is sympatric with the widespread pantropical cyanolichen Coccocarpia palmicola in cool and damp forests in Atlantic parts of Canada. After sampling co-occurring specimens of these lichens in Newfoundland, we quantified important hydration traits. We hypothesized that 1: these lichens restricted to wet forests have higher internal water holding capacity (WHCinternal) than what humid air and dewfall can provide, and 2: the rare E. pedicellatum has higher WHCinternal and / or WHCtotal than the widespread C. palmicola. Both hypotheses were supported: Mean WHCinternal across a wide thallus size range was 0.26 and 0.35 mm H2O in C. palmicola and E. pedicellatum, respectively; corresponding mean WHCtotal were 0.73 and 0.86 mm. These high WHC-levels could only be filled by liquid hydration sources. Because WHC strongly increased with thallus size, larger specimens needed even more water (1.7 mm), emphasizing these species’ dependency on rain and thus wet forests.

In this study, we investigated responses of the Photochemical Reflectance Index (PRI), and Normalized Difference Vegetation Index (NDVI) to gradual dehydration of several Antarctic lichen species (chlorolichens: Xanthoria elegans, Rhizoplaca melanophthalma, Physconia muscigena, cyanolichen: Leptogium puberulum), and a Nostoc commune colony from fully wet to a dry state. The gradual loss of physiological activity during dehydration was evaluated by chlorophyll fluorescence parameters. The experimental lichen species differed in thallus color, and intrathalline photobiont. In the species that did not exhibit color change with desiccation (X. elegans), NDVI and PRI were more or less constant (mean of 0.25, − 0.36, respectively) throughout a wide range of thallus hydration status showing a linear relation to relative water content (RWC). In contrast, the species with apparent species-specific color change during dehydration exhibited a curvilinear relation of NDVI and PRI to RWC. PRI decreased (R. melanophthalma, L. puberulum), increased (N. commune) or showed a polyphasic response (P. muscigena) with desiccation. Except for X. elegans, a curvilinear relation was found between the NDVI response to RWC in all species indicating the potential of combined ground research and remote sensing spectral data analyses in polar regions dominated by lichen flora. The chlorophyll fluorescence data recorded during dehydration (RWC decreased from 100 to 0%) revealed a polyphasic species-specific response of variable fluorescence measured at steady state—Fs, effective quantum yield of photosystem II (ΦPSII), and non-photochemical quenching (qN). Full hydration caused an inhibition of ΦPSII in N. commune while other species remained unaffected. The dehydration-dependent fall in ΦPSII was species-specific, starting at an RWC range of 22–32%. Critical RWC for ΦPSII was around 5–10%. Desiccation led to a species-specific polyphasic decrease in Fs and an increase in qN indicating the involvement of protective mechanisms in the chloroplastic apparatus of lichen photobionts and N. commune cells. In this study, the spectral reflectance and chlorophyll fluorescence data are discussed in relation to the potential of ecophysiological processes in Antarctic lichens, their resistance to desiccation and survival in Antarctic vegetation oases.

The importance of N2-fixing arboreal cyanolichens to the nitrogen (N)-balance of sub-boreal interior hybrid spruce (Picea glauca × engelmannii) and subalpine fir (Abies lasiocarpa) forests was examined at field sites in central BC, Canada. Host trees were accessed by a single-rope climbing technique and foliage as well as arboreal macrolichen functional groups were sampled by branch height in eight random sample trees from each of two high (High Cyano) and two low (Low Cyano) cyanolichen abundance sites for a total of 32 sample trees. Natural abundances of stable isotopes of N (15N, 14N) and carbon (13C, 12C) were determined for aggregate host tree and epiphytic lichen samples, as well as representative samples of upper organic and soil horizons (Ae and Bf) from beneath host trees. As expected, N2-fixing cyanolichens had 2–6-fold greater N-contents than chlorolichens and a δ15N close to atmospheric N2, while foliage and chlorolichens were more depleted in 15N. By contrast, soils at all trees and sites were 15N-enriched (positive δ15N), with declining (not significant) δ15N with increased tree-level cyanolichen abundance. Lichen functional groups and tree foliage fell into three distinct groups with respect to δ13C, the tripartite cyanolichen Lobaria pulmonaria (lightest), host-tree needles (intermediate), and bipartite cyanolichens, hair (Alectoria and Bryoria spp.) and chlorolichens (heaviest). Branch height of host trees was an effective predictor of needle δ13C. Our results showed a modest positive correlation between host tree foliage N and cyanolichen abundance, supporting our initial hypothesis that higher cyanolichen abundances would elevate host tree foliar N. Further study is required to determine if high cyanolichen abundance enhances host tree and/or stand-level productivity in sub-boreal forests of central BC, Canada.

High‐latitude terrestrial ecosystems face the triple threats of climate warming, increased exposure to UV arising from polar ozone depletion, and deforestation. Lichen communities of southernmost Chile are recognized for their high diversity, which includes nitrogen‐fixing cyanolichens. Such lichens are common on forest trees, contribute nitrogen to forests, and are sensitive to exposure following deforestation (widespread in this region). In a pilot study of exposure effects on tree lichens, using nondestructive imaging methods, we compared lichen communities on trunks of isolated vs. forest tree trunks of southern Chilean beech ( Nothofagus dombeyi , Nothofagaceae). We chose trees of similar diameter and trunk lean angle in conserved forest and nearby logged meadow on Navarino Island, XII Region Magallanes and Chilean Antarctica, Chile, within the annual southern ozone hole. Ninety‐five percent of cyanolichen records, including Nephroma antarcticum , and 66% of records for other foliose lichens were from the forest, whereas pendulous usneoid lichens dominated N. dombeyi bark at the meadow site. Limitation of cyanolichen growth on isolated trees could affect ecosystem function in this poorly studied habitat. Possible factors contributing to strong community differences were increased light intensity, UV radiation, and wind stress, plus limited ability of lichens to colonize isolated trees in the logged meadow. UV radiation was likely an important stressor for some lichen species but not others. We recommend more extensive monitoring to pinpoint causes of differing lichen communities, and we encourage better protection of bark‐dwelling lichens in southern hemisphere regions facing multiple threats.

Reasonable lichen growth rates are required to maintain the important ecosystem functions provided by epiphytic lichen populations. Previously, lichen growth has mainly been quantified in boreal forests. Thus, there is a need for comparable studies from Mediterranean forests. We used reciprocal transplantation to compare relative biomass (RGR) and thallus area (RTAGR) growth rates of the cephalolichen Lobaria pulmonaria and the cyanolichen Lobarina scrobiculata (n = 720 thalli) in two Mediterranean oak forests. Both juvenile and reproductive thalli were transplanted for 334 days at the base and at breast height of random trees in both forests. We measured functional traits, specific thallus mass (STM) and water holding capacity (WHC), to search for adaptation/acclimation patterns between regions and between local stands. Linear Mixed Models were used to assess the effects of (1) forest, (2) height on the trunk and (3) reproductive stage on RGR, RTAGR, and functional traits. Lobaria pulmonaria grew faster than L. scrobiculata, consistent with its more flexible hydration traits. Growth rates in both species were fastest in juveniles at the trunk bases, consistent with trade-offs between (1) growth and reproduction and (2) humidity availability and distance from the ground. In L. pulmonaria, STM increased with increasing evaporative demands, consistent with acclimation mechanisms. Fundamental and realized niches differed in L. scrobiculata, indicating that high abundance does not necessarily coincide with optimal growth habitat. Both species grew as fast in drier and warmer Mediterranean forests as reported from boreal forests, presumably because local conditions during hydration periods differ less between macroclimate regions than average climatic parameters, and/or because dew formation is frequent, particularly near the ground. Furthermore, STM and WHC of lichens in Mediterranean forests were high, thus partly compensating for the drier conditions. This study improves our understanding of mechanisms underlying epiphytic lichen growth in Mediterranean climates.

We explore relative growth rates (RGRs) and carbon-based secondary compounds (CBSCs) in epiphytic lichens along height-above-the-ground gradients. The chlorolichen (Letharia vulpina (L.) Hue), the cephalolichen (Lobaria pulmonaria (L.) Hoffm.), and the cyanolichens (Lobaria hallii (Tuck.) Zahlbr., Nephroma helveticum Ach.) were attached to branches at 0.5–3.0 m heights of young spruce trees transplanted for 1 year in forest gaps and in old meadows of an inland valley in British Columbia. Cephalolichen and cyanolichen RGRs were highest in forest gaps, whereas the chlorolichen grew faster in meadows with twice as much light as forest gaps. Transplantation height did not influence lichen temperature or RGRs, despite height-dependent light increases. CBSCs were highest in the chlorolichen (13%), followed by the cephalolichen (5%) and the cyanolichens (1% and 0%). CBSC concentrations increased with thallus size, and were significantly higher in forest gaps mainly for L. pulmonaria. Only one minor CBSC in each species varied with height. The slow growth of cephalolichen and cyanolichens in meadows is consistent with these lichens’ preferences for forested habitats. Cold air ponding from snow-capped mountains was probably strong enough to form enough nocturnal dew to support reasonable lichen growth at all heights. The high species-specific and the low habitat-specific CBSC variations are consistent with constitutive CBSC defense levels in studied lichens.

Lichens symbioses, commonly described as fungal partnerships with a photosynthetic partner (green algae and/or cyanobacteria) are associated with a diverse bacterial community. Whereas the microbiome diversity and function of terrestrial lichens has been well studied, knowledge about the non-photosynthetic bacteria associated with marine lichens is still scarce. Since there is a clear vertical zonation of lichens across the littoral belt we hypothesized that this correlates with significant variations of bacterial communities associated with these lichens. To test this hypothesis, 16S rRNA gene illumina sequencing was used to assess the culture-independent bacterial diversity in the strictly marine cyanolichen species Lichina pygmaea and Lichina confinis, and the maritime chlorolichen species Xanthoria sp. collected from the French Brittany coast. These species occupied the lower eulittoral, upper eulittoral and supralittoral zones respectively. Inland terrestrial cyanolichens from Austria were also analysed as for the marine lichens to examine further the impact of habitat/lichen species on the associated bacterial communities. The L. confinis and L. pygmaea communities were significantly different from those of the terrestrial lichens with the Bacteroidetes phylum accounting for 50% of the sequences, whereas Alphaproteobacteria, notably Sphingomonas, dominated the terrestrial lichens. Bacterial communities associated with the two Lichina species were significantly different sharing only 33 core OTUs, half of which were affiliated to the Bacteroidetes genera Rubricoccus, Tunicatimonas and Lewinella, suggesting an important role of these species in the marine lichen symbiosis. The presence of multiple OTUs of these genera that were differentially distributed between the two Lichina species, could be suggestive of ecological speciation driven by adaptation to the different conditions of the intertidal and supratidal zones. Marine cyanolichens showed a higher abundance of OTUs likely affiliated to moderately thermophilic and/or radiation resistant bacteria belonging to the Phyla Chloroflexi, Thermi, and the families Rhodothermaceae and Rubrobacteraceae when compared to those of terrestrial lichens. This most likely reflects the exposed and highly variable conditions to which marine lichens are subjected to daily.

Cyanolichens are an assemblage of fungi and cyanobacteria from diverse, cosmopolitan habitats. Typically composed of a single species of cyanobacterium, with or without another eukaryotic alga, here we present two novel cyanobionts isolated from an undescribed tripartite lichen. This endolithic lichen was isolated from a granite cemetery tombstone from Jacksonville, FL, and contains two potentially nitrogen-fixing cyanobionts. Employing a total evidence approach, we characterized the cyanobionts using molecular (the 16S rDNA and ITS gene region), morphological, and ecological data. Phylogenetic analyses revealed two novel taxa: Brasilonema lichenoides and Chroococcidiopsis lichenoides, both of which fell within well-supported clades. To our knowledge, this represents the first instance of a tripartite lichen with two cyanobacterial and no eukaryotic members. These types of lichens may well represent an unexplored reservoir of cyanobacterial diversity. The specific epithets are proposed under the provisions of the International Code of Nomenclature for algae, fungi, and plants.

Lichen symbioses are defined as a symbiotic relationship between a mycobiont (generally an ascomycete) and one or more photobionts (green algae or/and cyanobacteria). It was proposed that cephalodia emancipation is an evolutionary driver for photobiont switch from chlorophyte to cyanobacteria. In this study we want to test the monophyly of cyanolichens and to measure the phylogenetic signal of the symbiotic relationship between cyanobacteria and a mycobiont partner in the lichen genus Pseudocyphellaria. This genus includes some species that have a chlorophyte as primary photobiont (and Nostoc in internal cephalodia), while others have only cyanobacteria. In a phylogenetic framework we measure the phylogenetic signal (or phylogenetic dispersion) as well as mapped photobiont switches performing stochastic character mapping. Results show that having cyanobacteria as main photobiont has a strong phylogenetic signal that follows a Brownian motion model. Seven clades in the phylogeny had an ancestor with cyanobacteria. Reversal to a green algae photobiont is rare. Several switches were estimated through evolutionary time suggesting that there was some flexibility in these traits along the phylogeny; however, close relatives retained cyanobacteria as main photobiont throughout the cyanolichen’s history. Photobiont switches from green algae to cyanobacteria might enhance ecotypical differentiation. These ecotypes could lead to several speciation events in the new lineage resulting in the phylogenetic signal found in this study. We give insights into the origin of lichen diversity exploring the photobiont switch in a phylogenetic context in Pseudocyphellaria s. l. as a model genus. Fil: Vidal Russell, Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Messuti, Maria Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina

Epiphytic lichens, comprising an important biodiversity component with significant functions in old boreal forests, are susceptible to logging. Leaving retention trees may partly compensate for the adverse effects of logging, but the impact of logging season on retained lichens is unknown. To identify the least harmful logging season seen from an epiphytic lichen perspective, we simulated logging events by transplanting two old forest model species – Lobaria pulmonaria (cephalolichen) and Lobaria scrobiculata (cyanolichen) – in summer, autumn, winter and spring, respectively. Lichens were collected in intact old forests and transplanted in clear-cuts. They were placed on five aspects (N, E, S, W, and top) on artificial stands covered with bark. They all gained biomass and area in the following year. However, logging in January resulted in subsequent higher relative growth rates than in lichens being exposed to clear cuts in other seasons, consistent with clear seasonal logging effects. Aspect impacted lichen growth less than logging season, despite significant bleaching and chlorophyll contents in the most exposed aspects. The high annual growth rate and the low level of damage after transplantation to clear cuts during winter suggest that green tree retention (GTR) logging practices in winter can support life-boating of susceptible old forest lichen epiphytes. Logging simulation during other seasons than winter resulted in lower growth, implying higher risk of permanent damage. Successful use of GTR cannot compensate for the loss of epiphytes at timber harvest, but supports local retained lichen populations that subsequently may boost re-colonization of the young stand.

Vertical distribution, biomass abundance and nitrogen stocks of epiphytic macrolichens were examined in the two dominant tree species, interior hybrid spruce (Picea engelmannii Parry ex Engelm. x glauca (Moench) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.), in sub-boreal spruce forest ecosystems of central British Columbia. Lichens were contrasted between two different site types containing either high (High Cyano) or low (Low Cyano) epiphytic cyanolichen abundance. A single rope technique was used for canopy access and a ‘clump’ method was used to estimate the abundance of arboreal lichens at different heights within both canopy tree species for five functional groups: Bryoria spp., Alectoria sarmentosa, foliose chlorolichens, bipartite cyanolichens, and Lobaria pulmonaria (the only tripartite cyanolichen). In this way, the relationship between average lichen biomasses and tree height for each tree species were assessed. We determined that biomass was dependent on tree height and species, with a greater abundance of lichen appearing on fir trees (mean ± SD; 1588 ± 428 g tree−1) than the generally taller spruce trees (917 ± 422 g tree−1). Foliose chlorolichen biomass was more abundant in trees with low abundance of L. pulmonaria (777.1 ± 365.9 g tree−1) than those with a high abundance of L. pulmonaria (553.6 ± 400 g tree−1). Much of this increase in chlorolichen biomass in trees with low cyanolichen abundance was a result of greater chlorolichen abundances in lower canopy positions where cyanolichens would otherwise predominate. Although bipartite cyanolichens had a higher %N (∼3.2%N) than L. pulmonaria (2.3%N) of dry mass, there was a much higher abundance of L. pulmonaria in the canopy of High Cyano sites containing a larger amount of N (4.04 ± 0.95 kg N ha−1) than in all bipartite cyanolichens combined (2.33 ± 1.11 kg N ha−1) or any other lichen spp. Chlorolichens are poor competitors for lower branch positions when cyanolichens such as L. pulmonaria are abundant, the latter of potential importance for N inputs into N-limited sub-boreal forests of central BC.

Lichens result from symbioses between a fungus and either a green alga or a cyanobacterium. They are known to exhibit extreme desiccation tolerance. We investigated the mechanism that makes photobionts biologically active under severe desiccation using green algal lichens (chlorolichens), cyanobacterial lichens (cyanolichens), a cephalodia-possessing lichen composed of green algal and cyanobacterial parts within the same thallus, a green algal photobiont, an aerial green alga, and a terrestrial cyanobacterium. The photosynthetic response to dehydration by the cyanolichen was almost the same as that of the terrestrial cyanobacterium but was more sensitive than that of the chlorolichen or the chlorobiont. Different responses to dehydration were closely related to cellular osmolarity; osmolarity was comparable between the cyanolichen and a cyanobacterium as well as between a chlorolichen and a green alga. In the cephalodium-possessing lichen, osmolarity and the effect of dehydration on cephalodia were similar to those exhibited by cyanolichens. The green algal part response was similar to those exhibited by chlorolichens. Through the analysis of cellular osmolarity, it was clearly shown that photobionts retain their original properties as free-living organisms even after lichenization.

Photosynthesis was compared in two cyanobacterial lichens (Lobaria hallii and Peltigera praetextata) and two green algal lichens (Lobaria pulmonaria and Peltigera leucophlebia) exposed to red, green or blue light. Cyanolichens had substantially lower photosynthetic CO(2) uptake and O(2) evolution than the green algal lichens in blue light, but slightly higher photosynthesis in red and green light. The effective quantum yield of photosystem (PS) II (Φ(PSII)) decreased with increasing red and green light for all species, but in blue light this response occurred in green algal lichens only. Cyanolichen Φ(PSII) increased with increasing blue light at low irradiances, but decreased at stronger exposures. However, after adding red light the efficiency of blue light for photosynthetic O(2) evolution increased by 2.4 times. Because phycobilisomes associated with PSII have a low blue light absorption, our results are consistent with blue light absorption mainly by Chl in PSI. Thereby, unequal allocation of excitation energy between PSII and PSI results in low cyanolichen photosynthesis under blue light. This is new knowledge in the science of lichenology with important implications for e.g. the reliability of using Chl fluorometers with blue light for cyanolichens.

Spilonema was originally described to accommodate an unusual group of cyanolichens with thread-like, cushion-forming thalli, and has long been placed in Coccocarpiaceae based on ascomatal development. However, Spilonema is the only genus of Peltigerales to include species lichenized with the cyanobacterial genus Stigonema, and the evolutionary relationships of Spilonema to other genera in the family have yet to be tested using molecular data. We present evidence from combined nuclear 28S, 18S and mitochondrial 12S rDNA to confirm the placement of the core species of Spilonema (S. paradoxum and S. revertens) in Coccocarpiaceae. Our data further show that despite possessing a different genus of photobiont (Scytonema), the north Pacific endemic genus Spilonemella must be included within Spilonema, suggesting that closely related species of the genus have changed photobionts in the course of evolution. However, we recovered Spilonema dendroides, one of the only lichens known to associate with the cyanobacterial genus Hyphomorpha, as only distantly related to the Coccocarpiaceae. The evolutionary relationships of this species are as yet unclear but it may occupy a basal position in the Peltigerales. We create for this species the new genus Erinacellus T. Sprib., Muggia & Tønsberg.

Molybdenum (Mo) nitrogenase has long been considered the predominant isoenzyme responsible for dinitrogen fixation worldwide. Recent findings have challenged the paradigm of Mo hegemony, and highlighted the role of alternative nitrogenases, such as the vanadium-nitrogenase. Here, we first characterized homeostasis of vanadium (V) along with other metals in situ in the dinitrogen fixing cyanolichen Peltigera aphthosa. These lichens were sampled in natural sites exposed to various levels of atmospheric metal deposition. These results were compared with laboratory experiments where Anabaena variabilis, which is also hosting the V-nitrogenase, and a relatively close relative of the lichen cyanobiont Nostoc, was subjected to various levels of V. We report here that V is preferentially allocated to cephalodia, specialized structures where dinitrogen fixation occurs in tri-membered lichens. This specific allocation is biologically controlled and tightly regulated. Vanadium homeostasis in lichen cephalodia exposed to various V concentrations is comparable to the one observed in Anabaena variabilis and other dinitrogen fixing organisms using V-nitrogenase. Overall, our findings support current hypotheses that V could be a more important factor in mediating nitrogen input in high latitude ecosystems than previously recognized. They invite the reassessment of current theoretical models linking metal dynamics and dinitrogen fixation in boreal and subarctic ecosystems.

The presence of the foliose cyanolichen Sticta sylvatica in eastern North America has been called into question due to the absence of high-quality, verifiable material and the common misuse of its name. Recently, specimens collected in the Great Smoky Mountains have been verified as having the typical S. sylvatica morphology. Although molecular data remain inconclusive regarding the entity's genetic distinctiveness from the phenotypically dissimilar S. limbata, we argue that the decline in the abundance of this morphological entity worldwide along with the need for further genetic study make continued conservation efforts imperative.

In order to evaluate the self-shading protection for inner photobionts, the photosynthetic activities of three crust lichens were detected using Microscope-Imaging-PAM. The false color images showed that longitudinal photosynthetic gradient was found in both the green algal lichen Placidium sp. and the cyanolichen Peltula sp. In longitudinal direction, all the four chlorophyll fluorescence parameters Fv/Fm, Yield, qP, and rETR gradually decreased with depth in the thalli of both of these two lichens. In Placidium sp., qN values decreased with depth, whereas an opposite trend was found in Peltula sp. However, no such photosynthetic heterogeneity was found in the thalli of Collema sp. in longitudinal direction. Microscope observation showed that photobiont cells are compactly arranged in Placidium sp. and Peltula sp. while loosely distributed in Collema sp. It was considered that the longitudinal photosynthetic heterogeneity was ascribed to the result of gradual decrease of incidence caused by the compact arrangement of photobiont cells in the thalli. The results indicate a good protection from the self-shading for the inner photobionts against high radiation in crust lichens.

In the revegetation region of Shapotou (at the southeastern edge of Tengger Desert), biological soil crusts (BSCs) generally develop and succeed from cyanobacterial soil crusts (CSCs) to lichen soil crusts (LSCs). Based on the different dominant lichens on crust surface, LSCs were further divided into cyanolichen soil crusts (CLSCs) and green algae lichen soil crusts (GLSCs). In this study, the microstructures and photosynthetic diurnal changes in both CLSCs and GLSCs were investigated using the microscopic observation and chlorophyll fluorescence techniques. The results showed the different types of LSCs have different surface morphological characteristics and inner structures due to the different biological compositions. Compared with the CLSCs, GLSCs had a higher photosynthetic efficiency, including the maximum photosynthetic efficiency (Fv/Fm) and effective photosynthetic efficiency (Phi(PSII)), which in the final analysis was considered to be closely correlated with the different photosynthetic characteristics between different photobiont types (green algae and cyanobacteria). In addition, similar to CSCs, a midday depression of photosynthetic efficiency was detected in LSCs, although the depression extents were different in different types of LSCs. In conclusion, the occurrence of midday depression of photosynthetic efficiency might be a stress effect and also an adaptation strategy of LSCs to adversity, especially the high light intensity and temperature at noon. (C) 2013 Elsevier Masson SAS. All rights reserved.

Acetone-extractable carbon based secondary compounds (CBSCs) were quantified in two epiphytic lichens to study possible effects of external factors (season and aspect) on secondary chemistry and to relate defense investments to biomass growth and changes in specific thallus mass (STM). At the end of four separate annual cycles starting in each of the four seasons, the cyanolichen Lobaria scrobiculata and the cephalolichen Lobaria pulmonaria (green algae as the primary photobiont and with localized Nostoc in internal cephalodia) were monitored in their natural forest habitats and after being transplanted at three contrasting aspects in open sites. Season strongly influenced most CBSCs. Medullary CBSCs in both species were twice as high in summer as in winter. Aspect hardly affected major CBSCs, whereas transplantation from forest to clear-cut slightly reduced these compounds. No major CBSCs in any species showed a trade-off with growth rate. Dry matter- as well as thallus area-based medullary CBSC contents increased with STM. The cortical usnic acid strongly increased with growth rate and followed spatial, but not seasonal variations in light exposure. Maximal CBSC levels during seasons with most herbivores is consistent with the hypothesis inferring that herbivory is a major selective force for CBSCs. Lack of trade-off between growth and defence investments suggests that these two processes do not compete for photosynthates.

Foliose lichens with cyanobacterial bionts (bipartite and tripartite) form a distinct assemblage of epiphytes strongly associated with humid microclimatic conditions in inland British Columbia. Previous research showed that these cyano- and cephalolichen communities are disproportionately abundant and species-rich on conifer saplings beneath Populus compared to beneath other tree species. More revealing, lichens with cyanobacterial bionts were observed beneath Populus even in stands that did not otherwise support them. We experimentally test the hypothesis that this association is due to the interception of glucose-rich nectar that is exuded from Populus extra-floral nectaries (EFN). Using CO2 flux measurements and phospholipid fatty acid (PLFA) analysis with experimental applications of 13C6-labeled glucose, we demonstrate that cyano- and cephalolichens have a strong respiratory response to glucose. Lichens treated with glucose had lower net photosynthesis and higher establishment rates than control thalli. Furthermore, lichens with cyanobacterial bionts rapidly incorporate exogenous 13C into lichen fatty acid tissues. A large proportion of the 13C taken up by the lichens was incorporated into fungal biomarkers, suggesting that the mycobiont absorbed and assimilated the majority of applied 13C6 glucose. Our observations suggest that both cyanolichens and cephalolichens may utilize an exogenous source of glucose, made available by poplar EFNs. The exogenous C may enable these lichens to become established by providing a source of C for fungal respiration despite drought-induced inactivity of the cyanobacterial partner. As such, the mycobiont may adopt an alternative nutritional strategy, using available exogenous carbon to extend its realized niche.

Cryptogamic species and their associated cyanobacteria have attracted the attention of biogeochemists because of their critical roles in the nitrogen cycle through symbiotic and asymbiotic biological fixation of nitrogen (BNF). BNF is mediated by the nitrogenase enzyme, which, in its most common form, requires molybdenum at its active site. Molybdenum has been reported as a limiting nutrient for BNF in many ecosystems, including tropical and temperate forests. Recent studies have suggested that alternative nitrogenases, which use vanadium or iron in place of molybdenum at their active site, might play a more prominent role in natural ecosystems than previously recognized. Here, we studied the occurrence of vanadium, the role of molybdenum availability on vanadium acquisition and the contribution of alternative nitrogenases to BNF in the ubiquitous cyanolichen Peltigera aphthosa s.l. We confirmed the use of the alternative vanadium-based nitrogenase in the Nostoc cyanobiont of these lichens and its substantial contribution to BNF in this organism. We also showed that the acquisition of vanadium is strongly regulated by the abundance of molybdenum. These findings show that alternative nitrogenase can no longer be neglected in natural ecosystems, particularly in molybdenum-limited habitats.

Low phosphorus (P) supply frequently has been shown to limit the abundance and activity of nitrogen (N)-fixing organisms, potentially constraining N inputs to ecosystems. Previous research in a montane Hawaiian forest has shown that ground-level P-fertilization led to significant increases in the population size of epiphytic N-fixing lichens (cyanolichens), as well as a shift in community composition from crustose to leafy species. In this study, we ask whether these changes in the cyanolichen community have resulted in increased N inputs to the forest, and also whether the very high levels of P in the canopy of P-fertilized forest stimulate individual lichen fixation rates over those of lichens from a nearby unfertilized reference forest. We used acetylene reduction (AR) assays to measure the fixation rates of 14 cyanolichen species from P-fertilized forest, and calibrated these rates by measuring15N2fixation incorporation in four species. We found that the ratio of acetylene reduced to N fixed ranged from 2.4 ± 0.4 inPseudocyphellaria crocatato 9.3 ± 2.4 inLeptogium denticulatum. Nitrogen fixation rates in the P-fertilized forest ranged from 0.64 ± 0.05 nmol N cm−2h−1inNephroma helveticumto 3.97 ± 1.48 nmol N cm−2h−1inParmeliella nigrocincta. Fixation rates did not vary greatly among species from P-fertilized forest. We compared these P-fertilized rates to those of 10 species from the reference forest, and found that mass-based fixation rates of P-fertilized lichens were not greater than those of lichens from the unfertilized forest. Using the measured AR rates, we estimate that the P additions increase cyanolichen N inputs to the forest 30-fold, from ~0.3 kg N ha−1y−1to ~9 kg N ha−1y−1. These results suggest that P additions to this ecosystem increase N inputs primarily by increasing the abundance of cyanolichens, and that shifts in cyanolichen community composition and changes in individual fixation rate were of lesser importance in determining ecosystem N inputs.

International audience; Mycosporine-like compounds, comprising mycosporines and mycosporine-like amino acids (MAAs) are UV protecting secondary metabolites described in organisms such as fungi, algae, cyanobacteria or animals. Lichens however, were only poorly investigated for such constituents so far. Here, a method for the characterization of mycosporines and MAAs in purified aqueous extracts, involving HPTLC coupled to spectrophotodensitometry, HPLC-DAD-MS(n) and UPLC-HRMS analysis, is described. This optimized protocol was validated on three algae and one cyanolichen containing known MAAs and mycosporines, and then applied to 18 cyanolichen species. Analyses revealed the presence of five already described mycosporine-like compounds in the investigated species, including mycosporine serinol in Lichina and Peltigera species and mycosporine glutamicol in Degelia plumbea. Apart from that, eight unknown mycosporine-like compounds were detected and tentatively characterized on the basis of their DAD spectra and their MS(n) and HRMS data: two in the alga Porphyra dioica and six in cyanolichen species belonging to the genera Degelia, Nephroma and Stereocaulon. From Nephroma laevigatum, the mycosporine hydroxyglutamicol was preparatively isolated and identified through HRMS, 1D and 2D NMR spectroscopic data. The optimized analytical protocol allowed the characterization of mycosporine-like compounds in small amounts of material and confirmed the potential of cyanolichens as a source of mycosporine compounds. It should also be applicable to investigate lichen species with green algae photobionts for mycosporine-like compounds.

Erioderma mollissimum is a rare cyanolichen found on the foggy Atlantic coast of Canada. The rarity of E. mollissimum and the potential threat from human impact has led to conservation concern for this species in Canada. Recent finds on the island of Newfoundland suggest that the distribution of E. mollissimum may be wider than historically known. In order to better understand the environmental factors affecting distribution and to direct future search efforts a Mahalanobis predictive distribution model using a geographical information system (GIS) was developed for Atlantic Canada. The model suggests that only a small part of this region is suitable for E. mollissimum. This study provides an example of an alternative modeling technique to the traditional statistical methods for predicting lichen distribution.

Lichen diversity along the Mississippi River in the Minneapolis-St. Paul urban area was studied in 2008 by sampling 37 localities along the 110-kilometer river basin, resulting in 76 species, which are thought to represent 80% of the complete flora. A significant decrease in lichen diversity toward the urban part of the river basin, as well as the presence of only one cyanolichen suggests that urban factors, e.g. air pollutants and habitat destruction may be affecting lichen diversity. In addition, lichen diversity has significantly decreased from that of 112 years ago, when a study by Fink reported 113 species, and a higher number of genera represented by a single species.