Are there any substrate preferences in aquatic hyphomycetes ?

Aquatic hyphomycete assemblages on different types of plant litter in Belarus rivers and streams were investigated to determine whether any substrate specificity or preferences were apparent. Pooled samples (146) from 92 watercourses were analysed. Colonization coefficients were computed for each fungal taxa and substrate type and the resulting matrix analysed with principal component analysis and cluster analysis. The results demonstrate that some substrates support relatively specific aquatic hyphomycete assemblages and it is possible to ordinate plant litter types by means of their fungal complexes. This suggests selective colonization by fungi, i.e. substrate preferences at least in some species. Wood and grass blades bear fungal assemblages clearly distinct from those supported by tree leaf litter (with higher percentage of scolecosporous and antagonistic species). Ordination of plant litter types could be explained by size of substrate units, their chemical composition (in particular lignin content) and, consequently, breakdown rate that affects fungal colonization.