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

Short spatial and temporal scale patterns of fish assemblages in a subtropical rainforest mountain stream

The fish fauna of a subtropical mountain stream in Argentina was surveyed for the first time. The abundance and occurrence of species were explored considering variation in hydrology, seasonality and the abiotic environment. We collected 221 individuals of 23 species from 10 families and four orders. Small sized species and small individuals dominated the fish fauna. The small characid Astyanax saguazu was the most conspicuous species. Hydrology, seasonal changes in water temperature and variation in water conductivity affected the abundance and distribution of fish. Hypobrycon maromba is recorded in Argentina for the first time.Fil: Rosso, Juan Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Mabragaña, Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Avigliano, Esteban. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Centro de Estudios Transdisciplinarios del Agua; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Schenone, Nahuel Francisco. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Centro de Estudios Transdisciplinarios del Agua; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Diaz de Astarloa, Juan Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentin