Assessing the legacy of land use trajectories on stream fish communities of southern Brazil.

Loss of native vegetation cover in the watershed is known to affect stream fish communities. However, community response may not occur immediately after land cover change, and may become apparent only years later. In this study, we investigated how a c.a. 30-year (1985–2017) historical trajectory of native vegetation loss affected fish communities in 47 streams of southern Brazilian grasslands. We tested whether current species richness and composition would be more related to past or to recent natural vegetation cover. We then defined trajectories of vegetation loss and tested whether different attributes (frequency, magnitude and duration of disturbance) affected particular species and functional groups. We found that current species richness and composition were more related to past than to current vegetation cover. However, we also observed that responses of particular species and functional groups were dependent on specific trajectory attributes. We concluded that present fish community characteristics may respond not only to past watershed conditions but also to how watershed conditions have changed over the time. Exploring land use trajectories seems a promising approach for improving our understanding of landscape effects on stream ecosystems, as well as the predictability of present landscape management and planning on freshwater communities. [ABSTRACT FROM AUTHOR]