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Several investigations on lichen photobionts (PBs) after exposure to simulated or real-space parameters consistently reported high viability and recovery of photosynthetic activity. These studies focused on PBs within lichen thalli, mostly exposed in a metabolically inactive state. In contrast, a recent study exposed isolated and metabolically active PBs to the non-terrestrial stressor UVC sub(254 nm) and found strong impairment of photosynthetic activity and photo-protective mechanisms (Meesen et al. in 2014b). Under space and Mars conditions, UVC is accompanied by other stressors as extreme desiccation and low temperatures. The present study exposed the PBs of Buellia frigida and Circinaria gyrosa, to UVC in combination with desiccation and subzero temperatures to gain better insight into the combined stressors' effect and the PBs' inherent potential of resistance. These effects were examined by chlorophyll a fluorescence which is a good indicator of photosynthetic activity (Luettge & Buedel in 2010) and widely used to test the viability of PBs after (simulated) space exposure. The present results reveal fast recovery of photosynthetic activity after desiccation and subzero temperatures. Moreover, they demonstrate that desiccation and cold confer an additional protective effect on the investigated PBs and attenuate the PBs' reaction to another stressor - even if it is a non-terrestrial one such as UVC. Besides other protective mechanisms (anhydrobiosis, morphological-anatomical traits and secondary lichen compounds), these findings may help to explain the high resistance of lichens observed in astrobiological studies.

In the past decade, various astrobiological studies on different lichen species investigated the impairment of viability and photosynthetic activity by exposure to simulated or real space parameters (as vacuum, polychromatic ultraviolet (UV)-radiation and monochromatic UVC) and consistently found high post-exposure viability as well as low rates of photosynthetic impairment (de Vera et al. 2003, 2004a; 2004b; de la Torre et al. 2010; Onofri et al. 2012; Sanchez et al. 2012, 2014; Brandt et al. 2014). To achieve a better understanding of the basic mechanisms of resistance, the present study subdued isolated and metabolically active photobionts of two astrobiologically relevant lichens to UVC sub(254 nm), examined its effect on photosynthetic activity by chlorophyll a fluorescence and characterized the UVC-induced damages by quantum yield reduction and measurements of non-photochemical quenching. The results indicate a strong impairment of photosynthetic activity, photoprotective mechanisms and overall photobiont vitality when being irradiated in the isolated and metabolically active state. In conclusion, the present study stresses the higher susceptibility of photobionts towards extreme environmental conditions as UVC-exposure, a stressor that does not occur on the Earth. By comparison with previous studies, the present results highlight the importance of protective mechanisms in lichens, such as morphological-anatomical traits (Meesen et al. 2013), secondary lichen compounds (Meesen et al. 2014) and the symbiont's pivotal ability to pass into anhydrobiosis when desiccating.

The genetic diversity of green algal photobionts (chlorobionts) in soil crust forming lichens was studied as part of the SCIN-project (Soil Crust InterNational). A total of 64 lichen samples were collected from four different sites along latitudinal and altitudinal gradients in Europe (Tabernas/Spain; Hochtor-Großglockner/Austria; Gynge Alvar/Sweden; Ruine Homburg/Germany). The dominant lichen species at all four sites was Psora decipiens, often occurring with Buellia elegans, Fulgensia bracteata, F. fulgens and Peltigera rufescens. Genetic identification of chlorobionts was carried out using the nuclear marker (nrITS) and a chloroplast marker (psbL-J). We found P. decipiens to be associated with several different species of Trebouxia and Asterochloris, although previously described to only have Asterochloris sp. The phylogenetic analyses revealed a high chlorobiont diversity with 12 well supported clades, including Trebouxia asymmetrica, T. jamesii, T. impressa and other, as yet taxonomically unidentified clades (Trebouxia sp. URa1-4, T. sp. URa6, T. sp. URa7-13). Additionally, five clades of Asterochloris were identified (A. magna, A. sp. URa14 -17). Most of the chlorobiont species appeared to be cosmopolitan, but five clades were unevenly distributed between the sampling sites with only Trebouxia being found in the warm and dry Spanish habitats and combinations of Trebouxia and Asterochloris in the cooler and more humid habitats. The wide range of chlorobiont species might contribute to the observed domination of P. decipiens at all four research sites of the SCIN project which range from a desert in Spain to an alpine site in the Alps of Austria.

(1) Biocrusts are key drivers of ecosystem functioning in drylands, yet our understanding of how climate change will affect the chemistry of biocrust‐forming species and their impacts on carbon (C) and nitrogen (N) cycling is still very limited. (2) Using a manipulative experiment conducted with common biocrust‐forming lichens with distinct morphology and chemistry (Buellia zoharyi, Diploschistes diacapsis, Psora decipiens and Squamarina lentigera), we evaluated changes in lichen total and isotopic C and N and several soil C and N variables after 50 months of simulated warming and rainfall reduction. (3) Climate change treatments reduced δs13C and C:N ratio in B. zoharyi, and increased δ15N in S. lentigera. Lichens had species‐specific effects on soil dissolved organic N (DON), NH4+, β‐glucosidase and acid phosphatase activity regardless of climate change treatments, while these treatments changed how lichens affected several soil properties regardless of biocrust species. Changes in thallus δ13C, N and C:N drove species‐specific effects on DON, NH4+, β‐glucosidase and acid phosphatase activity. (4) Our findings indicate that warmer and drier conditions will alter the chemistry of biocrust‐forming lichens, affecting soil nutrient cycling, and emphasize their key role as modulators of climate change impacts in dryland soils.

Summary It is well‐known that vascular plants have species‐specific effects on soil properties. However, little is known on how individual species forming biocrusts, communities dominated by lichens, mosses and cyanobacteria that are prevalent in many ecosystems world‐wide, affect microbial communities and soil variables related to nutrient cycling. We evaluated the relationship of six biocrust‐forming lichens (Buellia epipolia, Diploschistes diacapsis, Fulgensia subbracteata, Psora decipiens, Squamarina cartilaginea and Squamarina lentigera) with microbial abundance and multiple variables associated with soil nitrogen (N), carbon (C) and phosphorus (P) cycling and storage. We also evaluated whether the composition of lichen tissues (contents in C, N, P and polyphenols) is related to the C, N, P availability and microbial abundance in soils. Finally, we assessed what lichen species positively and negatively relate to soil fertility compared to bare ground areas without biocrusts. We found contrasted C, N, P availability and soil microbial abundance under the different biocrust‐forming lichens. Interestingly, inorganic P and amino acids were the most important factors differentiating lichen microsites. These differences in nutrient availability seem to be related to the C, N and P composition of the lichen tissues. For example, soils under D. diacapsis and P. decipiens, which had the lowest and highest C, N and P contents in their tissues, respectively, had the lowest and highest nutrient availability, respectively. We also found contrasted soil microbes abundance under the different soil lichens. For instance, F. subbracteata and D. diacapsis were negatively related to the abundance of bacteria compared to bare ground areas. Our results support the idea that, as found with vascular plants, biocrust‐forming lichens have species‐specific effects on soil microbial communities and C, N and P cycling. Thus, continuing considering biocrusts as a unique entity will only add confusion to our knowledge of how they control nutrient availability and microbial abundance in the ecosystems where this key community is prevalent. Lay Summary

The ventral surfaces of translucent rocks from hot desert pavements often harbor hypolithic microbial communities, which are mostly dominated by cyanobacteria. The Namib Desert fog belt supports extensive hypolithic colonization of quartz rocks, which are also colonized by lichens on their dorsal surfaces. Here, we aim to evaluate whether lichens colonize the ventral surface of the rocks (i.e., show hypolithic lifestyle) and compare the bacterial composition of these coastal hypolithic communities with those found inland. Fungal DNA barcoding and fungal and bacterial Illumina metabarcoding were combined with electron microscopy to characterize the composition and spatial structure of hypolithic communities from two (coastal and inland) areas in the Namib Desert. We report, for the first time, the structure and composition of lichen-dominated hypolithic communities found in the coastal zone of the Namib Desert with extensive epilithic lichen cover. Lichen modified areoles with inverted morphology of the genus Stellarangia (three lineages) and Buellia (two lineages) were the main components of these hypolithic communities. Some of these lineages were also found in epilithic habitats. These lichen-dominated hypolithic communities differed in structural organization and bacterial community composition from those found in inland areas. The hypolithic lichen colonization characterized here seems not to be an extension of epilithic or biological soil crust lichen growths but the result of specific sublithic microenvironmental conditions. Moisture derived from fog and dew could be the main driver of this unique colonization.

Eight species of Buellia s.l. containing xanthones are newly reported from China, including two species new to science (Buellia endoflavida and B. microareolata) and six records (B. concinna, B. mamillana, Stigmatochroma gerontoides, Tetramelas chloroleucus, T. geophilus and T. insignis) new to China. The genera Stigmatochroma and Tetramelas are also newly recorded from China. These species share the yellowish thallus with a UV+ yellow to orange reaction and can thus be easily separated from other buellioid taxa. Morphological, chemical and phylogenetic analyses were carried out to elucidate the placement of these species and to support the delimitation of the new taxa. Detailed descriptions and figures for the two new species are given and a key to all xanthone-containing buellioid species from China is provided.

In order to assess the origins of Antarctic lichens (local or long distance), we examined the population genetic structure of the endemic Antarctic lichen Buellia frigida across a latitudinal gradient of roughly 10° along the Transantarctic Mountains, Western Antarctica, using four microsatellite loci. All loci were highly polymorphic. Data were analysed as both biallelic (dikaryotic) and as haploid in order to determine whether different life-cycle phases could influence our interpretation of population structure. For biallelic data, allelic richness ( A ) ranged from 5.25 to 7.99 and measures of diversity suggested low levels of gene flow among most sites (e.g. F ST  =  G ST  = 0.09–0.31; D EST  = 0.03–0.7). For haploid data, allelic richness ( A ) ranged from 3.5 to 5.46, private allelic richness ( A r ) ranged from 0.81 to 2.05, Nei’s unbiased genetic distance ranged from 0.15 to 1.42 and Nei’s unbiased genetic identity ranged from 0.24 to 0.86 among locations. Two locations, the McMurdo Dry Valleys and Queen Maud Mountains, stand out as possible glacial refugia, with both having a high number of private alleles. Despite the high potential for wind-dispersed spores, it appears likely that successful colonisation in different areas is restricted. One possible explanation is that the combination of ice-free conditions and water availability occurs only during the short summer period when the prevailing wind patterns may influence dispersal pathways. Dispersal from the southernmost site (Queen Maud Mountains) appears particularly restricted and may be the result of dispersal barriers such as glaciers. We conclude that a combination of prevailing wind patterns and physical barriers restrict spore settlement and therefore dispersal and recruitment among regions.

The following corrections and amendments are made to the 2016 classification of lichenized fungi published in the previous issue of this journal. Four families are added: Harpidiaceae (Pezizomycotina incertae sedis), with the two genera Euopsis and Harpidium; Pleomassariaceae (Pleosporales), with the genus Splanchonema; Squamarinaceae (Lecanorales), with the two genera Herteliana (moved from Ramalinaceae) and Squamarina (moved from Stereocaulaceae); and Trichosphaeriaceae (Sordariomycetes: Trichosphaeriales), with the genus Cresporhaphis. The following previously overlooked genera are also added: Allophoron (Pezizomycotina incertae sedis), Cresporhaphis (Trichosphaeriaceae), Gabura (Arctomiaceae), Julella (Trypetheliaceae), Knightiella (Icmadophilaceae), Porpidinia (Lecideaceae), Protoroccella (Roccellaceae), Psoromidium (Pannariaceae) and Tremotylium (Arthoniales incertae sedis). The classification is adjusted for four genera: Asteroporum (moved from Pezizomycotina incertae sedis to Dothideomycetes incertae sedis), Eremastrella (moved from Psoraceae to Lecideaceae), Hosseusia (moved from Pannariaceae to Lecanoromycetes incertae sedis) and Joergensenia (moved from Lecanorales incertae sedis to Pannariaceae). Further, the following overlooked generic synonyms are listed: Buscalionia (= Marcelaria [nom. cons. prop.]), Degeliella (= Psoromaria), Dirinastrum (= Buellia), Gymnographa (= Phaeographis), Kroswia (= Fuscopannaria), Marfloraea (= Lepra), Medusulina (= Fissurina), and Phaeographina (= Pliariona); the genus Anapyrenium is discussed as a potential synonym of Thelomma. Species numbers are adjusted for nine genera: Austrella (Pannariaceae; 3 spp.), Icmadophila (Icmadophilaceae; 5 spp.), Lepidocollema (Pannariaceae; 23 spp.), Massalongia (Massalongiaceae; 6 spp.), Parmeliella (Pannariaceae; 70 spp.), Psoromidium (Pannariaceae; 1 spp.), Pyrgillus (Pyrenulaceae; 7 spp.), Siphula (Icmadophilaceae; 17 spp.) and Synarthonia (Arthoniales incertae sedis; 5 spp.). The fossil lichen Honeggeriella (complexa) is validated by adding MycoBank registration numbers, the validity of the genus name Pallidogramme (Graphidaceae) is discussed and confirmed, and the authorship of the name Thallinocarpon (Lichinaceae) is clarified. Several genera are (continued to be) considered non-lichenized, namely Chaenothecopsis (Eurotiomycetes: Mycocaliciales: Sphinctrinaceae), Limboria (newly lectotypified with L. constellata; Pezizomycotina incertae sedis), Naetrocymbe (Dothideomycetes: Pleosporales: Naetrocymbaceae), and Obryzum (Dothideomycetes incertae sedis: Obryzaceae); the status of the genus Pleurotrema (Dothideomycetes incertae sedis: Pleurotremataceae) is also discussed. Seven genera are corrected to have molecular data available: Adelolecia, Aspiciliopsis, Aspilidea, Crocodia, Parasiphula, Vezdaea and Xylopsora. With these corrections, the number of lichenized species is now tabulated at 19,409 and the number of fungal genera, families, and orders including lichens at 1,002, 119, and 40, respectively.

The Canary Islands are famous for their extraordinary biodiversity; however, lichenized algae have only been studied partially. Buellia zoharyi is a circum-Mediterranean/Macaronesian species that usually occurs in semi-arid areas of the Mediterranean, but occasionally some interesting communities of this species grow on basaltic lava flows in Lanzarote, Fuerteventura and Tenerife. Those three locations showed similar ecological conditions, but different mean annual temperatures. Here we applied a multidisciplinary approach to describe microalgae diversity from B. zoharyi covering the entire described range of distribution in the Canary Islands. Photobionts were characterized in symbiosis using molecular and microscopic techniques. Different Trebouxia spp. were detected as primary photobiont in each island ( Trebouxia cretacea -Fuerteventura, T. asymmetrica -Lanzarote and Trebouxia sp. ` arnoldoi ´-Tenerife). Coexistence of various Trebouxia spp. within a thallus were detected by using specific primers-PCR. Those three photobionts were isolated and cultured under laboratory conditions. Different phytohormone profiles were obtained in the isolated strains which suggest different internal signalling needs. In addition, we characterized the response of the isolated strains to different temperatures using chlorophyll fluorescence. T. asymmetrica did not modify their F v /fm values with respect to temperature acclimation. In contrast, Trebouxia sp. `arnoldoi’ and T. cretacea were more sensitive to changes in growing temperature decreasing Fv/fm at 17 °C. Our results indicate that B. zoharyi is flexible regarding the photobiont choice depending on the region, and suggest that bioclimatic factors could influence the myco/photobiont association patterns.