Temporal and Ecological Factors Influencing Aquatic Hyphomycetes in a Tropical Headwater Stream

Aquatic hyphomycetes are key decomposers in headwater streams, yet their temporal dynamics in tropical systems remain poorly understood due to the scarcity of long‐term studies. Here, we investigated the temporal variation of aquatic hyphomycete communities in a tropical Atlantic Forest stream over 5 years, evaluating the relative influence of intra‐ and interannual environmental factors on fungal richness, conidial density and community composition.

We combined field sampling with multivariate and modelling approaches (ANOSIM, BRT, TITAN and GAMMs) to disentangle temporal patterns and identify key environmental predictors. Our results show that interannual variation exerted a stronger influence on community structure than intra‐annual dynamics. Water chemistry and leaf litter quality were the main factors associated with fungal richness and density, whereas seasonal signals had limited explanatory power.

During seasonal environmental fluctuations, fungal communities showed remarkable temporal resilience and functional stability, with no collective community shift observed throughout the annual cycle. Indicator species such as Anguillospora filiformis , Tricelophorus monosporus and Amniculicola longissima displayed distinct responses to interannual environmental gradients, reinforcing their value as bioindicators of long‐term environmental change.

These findings highlight the predominance of long‐term environmental variability over seasonal dynamics in structuring tropical fungal communities and emphasize the importance of long‐term datasets for understanding ecosystem functioning in tropical streams.

This study provides key insights into the ecological roles of aquatic hyphomycetes in tropical streams by emphasizing the critical importance of long‐term approaches to unravel complex temporal patterns. Our results challenge the assumption of seasonality's dominance in tropical systems, offering a more nuanced understanding of fungal community responses to environmental change, which is essential for predicting ecosystem integrity under global climate change.