The replacement of native plants by exotic species may affect the colonization and reproduction of aquatic hyphomycetes.
The tropical riparian zone has a high diversity of plant species that produce a wide variety of chemical compounds, which may be released into streams. However, in recent decades there has been an extensive replacement of tropical native vegetation by Eucalyptus monocultures. Our objective was to compare fungal colonization of Eucalyptus camaldulensis leaves with fungal colonization of native plant species from riparian zones in Brazilian Cerrado (savannah) streams. The fungal colonization and enzymatic activity significantly influenced leaf litter decomposition. Fungal sporulation rates from leaf litter varied significantly with leaf species, with E. camaldulensis showing the highest sporulation rate (1226 conidia mg-1AFDM day-1) and leaf mass loss (23.2±0.9%). This species has the lowest lignin content and highest N concentration among the studied species. Among the studied native species, we observed the highest sporulation rate for Protium spruceanum (271 conidia mg-1AFDM day-1), Maprounea guianensis (268 conidia mg-1AFDM day-1) and Copaifera langsdorffii (196 conidia mg-1AFDM day-1). Overall, native plant species of the Brazilian Cerrado exhibited recalcitrant characteristics and a higher lignin:N ratio. Therefore, variations in the physical and chemical characteristics of the leaf litter could explain the higher decay rate and reproductive activity observed for E. camaldulensis. However, the detritus of this species were colonized almost exclusively by Anguillospora filiformis (99.6±0.4%) and exhibited a reduction in aquatic hyphomycetes species diversity. Our results suggest that the disturbance in the composition of riparian vegetation and consequently, in the diversity of leaf litter input into streams, could change the patterns and rates of leaf litter utilization by microbial decomposers. These changes may have important consequences in the processing of organic matter and, consequently, in the functioning of freshwater ecosystems.