Historical processes constrain metacommunity structure by shaping different pools of invertebrate taxa within the Orinoco basin.

Aim: To identify and characterize the distribution of invertebrate taxa in the Orinoco basin and how their distribution affects the metacommunity structure along the river network. Location: Meta and Guaviare sub‐basins, Orinoco basin, Colombia, South America. Methods: We characterized the invertebrate communities and environmental characteristics of 25 streams from six ecoregions in the Orinoco basin. The ecoregions present different historical evolution, altitude, slope, climate and vegetation features. We used multiplicative diversity partitioning to compare the contributions of riffle (α and β1), stream (β2) and ecoregional (β3) scales to the overall gamma diversity of the basin. We also applied the Elements of Metacommunity Structure framework to delineate metacommunity types and a distance‐based redundancy analysis to assess the relative relevance of environmental, spatial and ecoregional drivers in species compositions of invertebrate communities. Results: Streams showed significant differences in community composition among the ecoregions. Several discrete pools of invertebrate taxa occurred in the basin that largely matched the distribution of the ecoregions. Consequently, the metacommunity in the basin resembled a Clementsian idealized structure. The species composition of invertebrate communities was mostly explained by ecoregion type and its interaction with the local environment, particularly its physiographic features. Main conclusions: Historical and evolutionary processes have resulted in species pools differing between the ecoregions of the Orinoco basin. At the basin scale, the metacommunity structure seems to be constrained by ecoregional features rather than by spatial structure or the local environment. Hence, using the basin as a unit for biodiversity conservation and river management would not adequately reflect the diversity and distribution patterns in highly heterogeneous basins such as the Orinoco basin. [ABSTRACT FROM AUTHOR]