Phylogenetic analysis of LSU and SSU rDNA group I introns of lichen photobionts associated with the genera Xanthoria and Xanthomendoza (Teloschistaceae,lichenized Ascomycetes)

We studied group I introns in sterile cultures of selected groups of lichen photobionts, focusing on Trebouxia species associated with Xanthoria s. lat. (including Xanthomendoza spp.; lichen‐forming ascomycetes). Group I introns were found inserted after position 798 (Escherichia coli numbering) in the large subunit (LSU) rRNA in representatives of the green algal genera Trebouxia and Asterochloris. The 798 intron was found in about 25% of Xanthoria photobionts including several reference strains obtained from algal culture collections. An alignment of LSU‐encoded rDNA intron sequences revealed high similarity of these sequences allowing their phylogenetic analysis. The 798 group I intron phylogeny was largely congruent with a phylogeny of the internal transcribed spacer region, indicating that the insertion of the intron most likely occurred in the common ancestor of the genera Trebouxia and Asterochloris. The intron was vertically inherited in some taxa, but lost in others. The high‐sequence similarity of this intron to one found in Chlorella angustoellipsoidea suggests that the 798 intron was either present in the common ancestor of Trebouxiophyceae, or that its present distribution results from more recent horizontal transfers, followed by vertical inheritance and loss. Analysis of another group I intron shared by these photobionts at small subunit position 1512 supports the hypothesis of repeated lateral transfers of this intron among some taxa, but loss among others. Our data confirm that the history of group I introns is characterized by repeated horizontal transfers, and suggests that some of these introns have ancient origins within Chlorophyta.     

Rhamnogalactofuranan from the microalga Myrmecia biatorellae,symbiotic partner of Lobaria linita

A structural study of the cell wall polysaccharides of Myrmecia biatorellae, the symbiotic algal partner of the lichenized fungus Lobaria linita was carried out. It produced a cold-water insoluble rhamnogalactofuranan, with a (1 → 3)-linked β-d-galactofuranosyl main-chain, substituted at O-6 by single units of β-d-Galf, or by side-chains of 2-O- and 2,4-di-O-linked α-l-Rhap units. The structure of the polysaccharide was established by chemical and NMR spectroscopic analysis.     

Epiphytic lichen vegetation on Larix in the Italian Alps

Abstract

A synthesis of the epiphytic lichen vegetation on larch in the Italian Alps is presented. Vegetation types are described on the basis of a numerical classification of 291 relevés. They can be compared to a few well-known phytosociological unions found in other parts of the Alps. Some communities are restricted to subalpine areas with continental climate. Despite the homogeneity of the substrate, the flora is rich, with 98 species, several of which are rare, and hence of interest from a conservational point of view.     

Ecological investigations on lichen fields of the Central Namib

Number, geographic location, extent and characteristics of lichen fields were recorded within the Central Namib fog desert. Their occurrence is restricted to stable surfaces in the near coastal belt, while percentage cover changes with exposure, elevation and distance from the coastline. Maximum coverage of 70% was found at a distance of 5 km from the coast near Wlotzkas Baken. The highest biomass rate of 400 mg/m² was measured here at a distance of 1 km from the coast, where Teloschistes capensis appears as cushion growth type. Distribution patterns on hills, riverbeds and polygon structures are described. In general, fruticose and foliose lichens dominate on SW-exposed, ocean-facing habitats. Crustose species dominate on NE-E-exposed plots.Species composition and distribution, particularly the distribution of the fruticose species T. capensis (L. f.) Vain. ex Müll. Arg., were investigated in seventysix plots along twenty W-E transects in one lichen field near Wlotzkas Baken. T. capensis occurs in three different growth types: tuft, cushion and mat. Four zones are distinguished within the above lichen field, each dominated by a growth form indicating various influences of different climatic, geomorphic or biogenic parameters.     

Photosynthetic CO2-use efficiency in lichens and their isolated photobionts: the possible role of a CO2-concentrating mechanism

The CO₂ dependence of net CO₂ assimilation was examined in a number of green algal and cyanobacterial lichens with the aim of screening for the algal/cyanobacterial CO₂-concentrating mechanism (CCM) in these symbiotic organisms. For the lichens Peltigera aphthosa (L.) Willd., P. canina (L.) Willd. and P. neopolydactyla (Gyeln.) Gyeln., the photosynthetic performance was also compared between intact thalli and their respective photobionts, the green alga Coccomyxa PA, isolated from Peltigera aphthosa and the cyanobacterium Nostoc PC, isolated from Peltigera canina. More direct evidence for the operation of a CCM was obtained by monitoring the effects of the carbonic-anhydrase inhibitors acetazolamide and ethoxyzolamide on the photosynthetic CO₂use efficiency of the photobionts. The results strongly indicate the operation of a CCM in all cyanobacterial lichens investigated and in cultured cells of Nostoc PC, similar to that described for free-living species of cyanobacteria. The green algal lichens were divided into two groups, one with a low and the other with a higher CO₂-use efficiency, indicative of the absence of a CCM in the former. The absence of a CCM in the low-affinity lichens was related to the photobiont, because free-living cells of Coccomyxa PA also apparently lacked a CCM. As a result of the postulated CCM, cyanobacterial Peltigera lichens have higher rates of net photosynthesis at normal CO₂ compared with Peltigera aphthosa. It is proposed that this increased photosynthetic capacity may result in a higher production potential, provided that photosynthesis is limited by CO₂ under natural conditions.     

2-O-Methylconfluentinsäure: Ein neues depsid aus Lecidea fuscoatra

The lichen, Lecidea fuscoatra contains the new depside 2-O-methylconfluentinic acid. The structure of this compound follows front spectroscopical data and hydrolysis of its methyl ester to give olivetonic acid dimethyl ether and 2-O-methyl olivetol carboxylic acid.     

Spatial distribution of epiphytes on Populus tremula in relation to dispersal mode

Abstract. We examined if the spatial distribution of epiphytes in a forest stand differs between two sexually and three asexually dispersed species. As study species we have chosen two sexually dispersed species, the lichen Collema curtisporum and the bryophyte Orthotrichum speciosum, and three asexually dispersed species, the lichens C. furfuraceum and Leptogium saturninum and the bryophyte O. obtusifolium. All of these species grow on Populus tremula. In P. tremula stands, individual trees may be regarded as distinct patches for the studied species, while the stand represents a “landscape” of discrete patches. The study was performed in two relatively homogeneous forest stands. The study revealed that the asexually dispersed species were more common than the sexually dispersed. It was also shown that the sexually dispersed species were more aggregated than P. tremula in both stands. In contrast, the distribution of the asexually dispersed species mirrors, more or less, the distribution of their host, i.e. the spatial pattern shown by P. tremula. It is unlikely that the measured environmental variables strongly influenced the observed spatial distribution. Thus, we suggest that the different dispersal and establishment strategies were important in shaping the local distribution of the species.     

中国地衣新记录属———包被鳞核衣属

报道中国地衣- 新记录属———包被鳞核衣属。该属主要特征: 地衣体小鳞片状, 子囊器为子囊壳, 着生于地衣体小鳞片之间, 由一特化的外壁所包裹, 子囊孢子较大。     

When family matters: an analysis of Thelotremataceae (Lichenized Ascomycota: Ostropales) as bioindicators of ecological continuity in tropical forests

We analysed patterns of habitat and microhabitat preferences of 19 families (comprising 135 genera and 950 species) of crustose, corticolous lichens in Costa Rica (Arthoniaceae, Arthopyreniaceae, Coenogoniaceae, Graphidaceae, Lecanoraceae, Letrouitiaceae, Monoblastiaceae, Pertusariaceae, Physciaceae, Pilocarpaceae, Porinaceae, Pyrenulaceae, Ramalinaceae, Roccellaceae, Strigulaceae, Teloschistaceae, Thelenellaceae, Thelotremataceae, Trypetheliaceae), in order to test whether Thelotremataceae are suitable predictors of undisturbed tropical rain forest and can be used as bioindicators of ecological continuity. The dataset consisted of 12,215 specimen samples and six environmental parameters recorded for each sample (altitude, degree of seasonality, vegetation type, disturbance level, substrate nature, light exposure), which were analysed by a multivariate approach using principal component analysis (PCA). The analysis showed that three of the 19 families, Letrouitiaceae, Porinaceae, and Thelotremataceae, showed significant preferences for undisturbed primary to old growth secondary forest, fully shaded to semi-exposed microhabitats, and the bark of mature tree trunks, parameters assumed to be correlated with ecological continuity of closed rain forest habitats. Thelotremataceae had broader altitudinal range than Letrouitiaceae and Porinaceae and significantly higher genus and species diversity (16 genera, 130 species) compared to Porinaceae (4 genera, 40 species) and Letrouitiaceae (1 genus, 5 species). Our results support the hypothesis that Thelotremataceae perform best as predictors of undisturbed dry and lowland to montane rain forest and are the most suitable lichen bioindicators of ecological continuity in these ecosystems. In contrast, Lecanoraceae, Pertusariaceae, Physciaceae, and Teloschistaceae, were found to be predictors of disturbed and pioneer (micro-)habitats. We also found that, among a variety of parameters tested, the Index of Ecological Continuity (IEC), adapted to the use of Thelotremataceae in tropical forests, performs best in terms of predicting disturbance levels and site history. A semi-taxonomic approach identifying morphotypes rather than genera or species yielded the same results, making this method suitable for a broader spectrum of potential users.