Exotic riparian vegetation lowers fungal diversity but not leaf decomposition in Portuguese streams

1. We characterised the fungal communities of eight streams in Portugal, four bordered by native deciduous forest and four bordered by pure stands of Eucalyptus globulus . 2. Aquatic hyphomycete species richness and evenness, but not numbers of water‐borne conidia, of aquatic hyphomycetes were significantly lower in eucalypt bordered streams. 3. Multivariate analyses subdivided the fungal communities into two distinct groups corresponding to riparian vegetation. 4. Despite these differences in the dominant decomposer community, decay rates of eucalypt leaves (accounting for ≥98% of naturally occurring leaves in eucalypt bordered streams, absent in native forest) and chestnut leaves (occurring naturally in native forests) did not differ between the two groups of streams.