A multi‐network approach to assess how physical templates shape stream fish ecological strategies

Abstract The balance between dispersal (the movement of organisms between locations) and environmental filtering (the selection of species by local conditions) is central to metacommunity theory, although distinguishing their intertwined effects in nature remains a complex challenge. This study addressed this challenge by applying a multi‐network framework to a sampling dataset to assess the influence of spatial and environmental connectivity in the Pinhal River basin, Upper Paranapanema River, Brazil. The analysis revealed three primary ecological strategies—Dispersal Gateway, Mass Effect Dominated and Integrated Connector—arranged along a continuous functional gradient. The data suggest that species abundance is modulated by the interaction between these strategies and the underlying habitat connectivity. Dispersal Gateways are characterized as headwater specialists, while Mass Effect Dominated species show a pronounced dependency on dispersal connectivity. Finally, Integrated Connectors fulfil a ‘bridge’ function in the metacommunity, consistently associated with high Flow Betweenness values. Functional instability was observed in half of the studied stream reaches, with a concentration at headwater extremes; this suggests that these locations function as critical ecological transition thresholds within the dendritic network. Practical implication . Our framework partitions metacommunity dynamics and highlights the vulnerability of headwater ‘gateways’, providing a topological baseline for prioritizing the protection of essential flow connections in dendritic landscapes.