Descrição
Identifying the environmental gradients that control the functional structure of biological assemblages in reference
conditions is fundamental to help river management and predict the consequences of anthropogenic stressors. Fish metrics
(density of ecological guilds, and species richness) from 117 least disturbed stream reaches in several western Iberia river
basins were modelled with generalized linear models in order to investigate the importance of regional- and local-scale
abiotic gradients to variation in functional structure of fish assemblages. Functional patterns were primarily associated with
regional features, such as catchment elevation and slope, rainfall, and drainage area. Spatial variations of fish guilds were
thus associated with broad geographic gradients, showing (1) pronounced latitudinal patterns, affected mainly by climatic
factors and topography, or (2) at the basin level, strong upstream-downstream patterns related to stream position in the
longitudinal gradient. Maximum native species richness was observed in midsize streams in accordance with the river
continuum concept. The findings of our study emphasized the need to use a multi-scale approach in order to fully assess
the factors that govern the functional organization of biotic assemblages in ‘natural’ streams, as well as to improve
biomonitoring and restoration of fluvial ecosystems.
; Segurado, Pedro 
