Links between lichen morphology, internal/external water storage and distribution patterns are poorly known. We compared mass- (WC, % H2O) and area-based (WHC, mg H2O cm−2) hydration traits in seven pendent or shrubby Usnea species from oceanic to continental climates. All species held more external than internal water. Internal WHC and WC increased with specific thallus mass (STM, mg cm−2), while external WC decreased. Shrubby species had higher STM and total WHC than pendent ones. The continental Usnea hirta (shrubby) had the highest total and external storage; the suboceanic Usnea longissima (pendent) had the lowest internal storage. Morphology drives hydration traits and explains distributions of some Usnea species, but such traits did not distinguish oceanic from widespread species. Shrubby species maximize water storage and thus prolong hydration after rainfall events and/or hydration by dew. The low internal WHC in pendent species is likely an adaptation to frequent hydration in humid air.
Hair lichens (Alectoria, Bryoria, Usnea) with high surface-area-to-mass ratios rapidly trap moisture. By photography and scanning we examined how internal water storage depended on morphological traits in five species. Specific thallus mass (STM, mg DM cm(-2)) and water holding capacity (WHC, mg H2O cm(-2)) after shaking and blotting a fully hydrated thallus increased with thallus area. STM was approximate to 50% higher in Alectoria and Usnea thalli than in Bryoria. WHC was highest in Alectoria while percent water content of freshly blotted thalli was lowest in Usnea. Thallus area overlap ratio (TAO), assessing branch density of the thallus, was highest in the two thinnest Bryoria; lower in the thicker Usnea. Within species, hair lichens increased their water storage by increasing branch density rather than branch diameter. The taxonomically related genera Alectoria and Bryoria shared water storage characteristics, and differed from Usnea. Hair lichens in lower canopies have among the lowest water storage capacity reported in lichens.
Lichens hold water inside (internal pool) and outside their body (external pool). Yet, external pool size is not known in hair lichens dominating boreal forest canopies. Here we quantify morphological traits and internal/external water in two widespread Bryoria species along Picea abies canopy-height gradients: Bryoria fuscescens at 5-20 m and Bryoria capillaris at 15-20 m. Dry mass and specific thallus mass (STM) of intact B. fuscescens increased with height, while STM of individual branches did not. Maximum water holding capacity (mg H2O cm-2) increased with height, but did not differ between the species. Bryoria had much larger external (79-84% of total) than internal water pools, trapping water by dense clusters of thin, overlapping branches. They thus increase water storage in boreal forest canopies and influence hydrology. High external water storage extends hydration periods and improves lichen performance in upper canopies, and thereby contributes to the success of these hair lichens.
Ectomycorrhizal fungi produce low molecular weight organic compounds, supporting diverse microbial communities. To link mycorrhizal root exudation directly to bacterial responses, we used Scots pine exudates with (Suillus variegatus and Piloderma fallax) and without mycorrhiza as substrata for forest soil bacteria. Bacterial growth and vitality was monitored, and community composition determined using TRFLP, cloning and sequencing. We investigated if the amount of organic acids in exudates explained bacterial growth, and whether bacterial communities were influenced by pre-exposure to elevated atmospheric CO2. We demonstrated functional differences in bacterial growth rates related to CO2. There was a shift in the bacterial community (e.g. Burkholderia sp. and gamma-proteobacteria) toward organisms better able to rapidly utilize exudates when pine microcosms were pre-exposed to elevated CO2. Soil bacteria from all treatments tended to grow more abundantly and rapidly in exudates from Pilo derma -colonized seedlings, suggesting that the organic acids and/or unidentified compounds present supported greater growth.
Information about the global distribution of aquatic hyphomycetes is scarce, despite the primary importance of these fungi in stream ecosystem functioning. In particular, the relationship between their diversity and latitude remains unclear, due to a lack of coordinated surveys across broad latitudinal ranges. This study is a first report on latitudinal patterns of aquatic hyphomycete diversity associated with native leaf-litter species in five streams located along a gradient extending from the subarctic to the tropics. Exposure of leaf litter in mesh bags of three different mesh sizes facilitated assessing the effects of including or excluding different size-classes of litter-consuming invertebrates. Aquatic hyphomycete evenness was notably constant across all sites, whereas species richness and diversity, expressed as the Hill number, reached a maximum at mid-latitudes (Mediterranean and temperate streams). These latitudinal patterns were consistent across litter species, despite a notable influence of litter identity on fungal communities at the local scale. As a result, the bell-shaped distribution of species richness and Hill diversity deviated markedly from the latitudinal patterns of most other groups of organisms. Differences in the body-size distribution of invertebrate communities colonizing the leaves had no effect on aquatic hyphomycete species richness, Hill diversity or evenness, but invertebrates could still influence fungal communities by depleting litter, an effect that was not captured by the design of our experiment. (C) 2013 Elsevier Ltd and The British Mycological Society. All rights reserved.
Endophytes are microorganisms that live inside plants without causing visible symptoms, at least during some parts of their life cycle. We studied, for the first time, the combined effects of CO2 enrichment (700 ppm) and fungal endophyte inoculation on the growth, the concentrations of low-molecular weight phenolics, and condensed tannins of aspen (Populus tremula) seedlings. As expected, we found that the endophyte strain we inoculated was neutral to plant growth and was able to bypass major plant defences. In addition, CO2 enrichment alone boosted plant growth, but had only minor effects on plant phenolics. Neither did it affect the plant-endophyte relationship. Based on our findings, we suggest that the successful and asymptomatic colonization of endophytes that we found in aspen might be due to the endophytes' special attributes enabling them to thrive inside plant tissues and to avoid or counteract the plant's chemical defences.
We describe an accurate and efficient workflow for highly multiplexed paired-end Illumina sequencing of fungal full-length ITS amplicons. The impact of habitat and substratum conditions on leaf-inhabiting fungal communities was analysed. Fully vital and clearly senescent leaves of European beech (Fagus sylvatica) were sampled along an elevation gradient of about 1000 m in the Bavarian Alps, Germany, in autumn 2013. Surface-sterilised leaves were used for genomic DNA extraction, tagging-by-amplification and high-throughput sequencing. Significant correlation of community composition with elevation was observed. The mycobiome was little affected by the physiological state of the leaves, because only a partial shift of taxonomic composition was observed from vital towards clearly senescent leaves.