The cryptic lifestyle of most fungi necessitates molecular identification of the guild in environmental studies.Over the past decades, rapid development and affordability of molecular tools have tremendously improved insights of the fungal diversity in all ecosystems and habitats. Yet, in spite of the progress of molecular methods, knowledge about functional properties of the fungal taxa is vague and interpretation of environmental studies in an ecologically meaningful manner remains challenging. In order to facilitate functional assignments and ecological interpretation of environmental studies we introduce a user friendly traits and character database FungalTraits operating at genus and species hypothesis levels. Combining the information from previous efforts such as FUNGuild and Fun Fun together with involvement of expert knowledge, we reannotated 10210 and 151 fungal and Stramenopila genera, respectively. This resulted in a stand-alone spreadsheet dataset covering 17 lifestyle related traits of fungal and Stramenopila genera, designed for rapid functional assignments of environmental studies. In order to assign the trait states to fungal species hypotheses, the scientific community of experts manually categorised and assigned available trait information to 697413 fungal ITS sequences. On the basis of those sequences we were able to summarise trait and host information into 92623 fungal species hypotheses at 1% dissimilarity threshold.

Despite numerous studies on plant endophytes, little is known about fungal communities associated with different aboveground tissues of living trees. We used high-throughput sequencing to compare the diversity and community structure of fungi inhabiting leaves, branches and trunks of Alnus incana and Corylus avellana growing at three hemiboreal forest sites. Our analysis revealed that tree organs are the main determinants of the structure of fungal communities, whereas the effects of host species and locality remained secondary and negligible, respectively. The structure of fungal communities in trunks was the most distinct compared to that in leaves and branches. The foliar fungal communities were more similar within than between individual trees, implying that certain fungi may grow through parts of the tree crown. The weak effect of locality compared to host organs and species identity suggests that the structural variation of fungal communities in the aboveground parts of trees depends mainly on deterministic factors rather than dispersal limitation.

Bacterial and fungal endophytes form diverse communities and contribute to the performance and health of their host plants. Recent evidence suggests that both host related factors and environmental conditions determine the community structure of plant endophytes. Yet, we know little about their distribution patterns, and underlying community assembly mechanisms across plant compartments. Here we analysed the structure of bacterial and fungal communities associated with tree compartments as well as their underlying soils across 12 tree individuals in boreal forests. We found that the structure of bacterial and fungal communities depends more strongly on the vertical location of tree compartments rather than the locality, species, and individuals of host trees. Microbial communities showed much stronger host specificity in aboveground than belowground compartments. While having lower compartment community variability compared to fungi, bacterial communities were markedly more distinct between below- and aboveground components but not between hosts, reflecting the greater importance of environmental filtering rather than dispersal limitation and host identity in their community assembly. Our data suggest that spatial distance from soil as a major microbiome source contributes to the formation of microbiomes in plants, and that bacterial and fungal communities may follow contrasting assembly processes.

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