Tree canopies provide habitats for diverse and until now, still
poorly characterised communities of microbial eukaryotes. One of the
most general patterns in community ecology is the increase in species
richness with increasing habitat diversity. Thus, environmental
heterogeneity of tree canopies should be an important factor governing
community structure and diversity in this subsystem of forest
ecosystems. Nevertheless, it is unknown if similar patterns are
reflected at the microbial scale within unicellular eukaryotes
(protists). In this study, high-throughput sequencing of two prominent
protistan taxa, Cercozoa and Oomycota, was performed. For a
comprehensive assessment of their diversity across all ecological
compartments from forest soils to the canopy, group specific primers
were used. When taking OTU abundances into account, our results showed
highly dissimilar protistan communities within the investigated
microhabitats. We observed no pattern of nestedness, because the
majority of OTUs was present in all sampled microhabitats. According to
the microbiological tenet ‘Everything is everywhere, but,the environment selects’, habitat diversity strongly favoured
distinct protistan taxa in terms of abundance, but due to their almost
ubiquitous distribution the effect of species richness on community
composition was negligible.
Keywords : protists, canopies, metabarcoding, environmental
heterogeneity, forest ecosystems