Evenness modulates effects of the loss of plant litter from rare species on fungal decomposers in tropical streams

While most studies evaluating plant species diversity effects on in-stream fungal decomposers have focused on dominant species, our study simulated different rare species extinction scenarios. We assessed whether the loss of these species altered the fungal biomass and aquatic hyphomycete sporulation, diversity and taxonomic composition in two experiments: even experiment, where we used the same biomass for all species (i.e., even litter mixtures); and natural proportion experiment, where we kept proportions of plant species as found in stream leaf litter (i.e., natural litter mixtures). We found that the loss of litter from rare plant species reduced fungal biomass and the reduction was greater for natural litter mixtures, indicating that evenness modulated the effect of diversity on fungal biomass, possibly through resource dissimilarity. Our findings reveal the relevance of litter from rare plant species and of the maintenance of natural species proportions in tropical riparian forests for the functioning of stream ecosystems.