Fish Diversity and Water Quality in Streams of the Andean‐Amazonian Transition Zone Reflect Local Land Cover Rather Than Upstream Conditions

Landscapes are heavily influenced by anthropogenic activities, affecting land cover at different scales. Anthropogenic land cover affects downstream aquatic communities in the catchment area via runoff, often reducing diversity. Some landscapes are yet to be strongly influenced, such as where armed conflict has prevented human activities. Land cover in these areas may affect aquatic communities differently and serve as a reference for subsequent changes in land use. We sampled fishes and water temperature, pH, conductivity, and dissolved oxygen at 25 localities from the lightly influenced Andean‐Amazonian transition zone in Colombia when armed conflict ended. We used multivariate analysis to infer the effects of land cover on fish and water quality at three local scales (100, 500, and 1000 m radii) relative to upstream catchment land cover. We also evaluated predictors of species richness, effective diversity, and local contribution to β diversity via regressions. Local land cover predicted fish assemblages and water quality in the relatively pristine catchment areas better than upstream catchment land cover. We provided support that local drivers of fish assemblages and water quality become dominated by anthropogenic landscape effects upstream, and the shift may be a sensitive, early indicator of anthropogenic land use on streams. Both water quality and fish assemblages showed highest local correlation with 1000 m buffers over the 100 m and 500 m buffers. Our study represents a baseline for evaluating the effects of anthropogenic activities on relatively conserved streams. The streams from our study system serve as a model for other tropical and subtropical areas at risk of habitat transformation and degradation due to anthropogenic activities.