Influence of local and landscape environmental factors on alpha and beta diversity of macroinvertebrates in Andean rivers

Research on macroinvertebrate community structure in Andean rivers has been oriented towards describing patterns of alpha and gamma diversity by taking into account environmental predictors at local spatial scales (e.g., micro- and mesohabitats). However, the patterns of beta diversity and the importance of landscape-scale variables have been evaluated to a lesser extent. The objective of this study was to describe the patterns of alpha and beta diversity of benthic macroinvertebrates in the Andean rivers of the Orinoco basin and their relationship with local and landscape environmental variation. A stratified random sampling of macroinvertebrates was carried out at 40 sites (comprising an altitudinal range of between 500 and 2900 m.a.s.l.), local and landscape variables were measured. Our results showed that the variation of alpha diversity was influenced by local and landscape variables, which are directly and indirectly related to the contribution of sediments, substrate composition and flow velocity, providing a heterogeneity of habitats. Global beta diversity was explained by the combined effect of local and landscape variables. Regarding the beta diversity phenomena, turnover was predominant while nestedness presented a minor contribution and both were explained in greater proportion by local descriptors and some landscape variables, specifically those of a geomorphological nature. Our results concur with the view of an environmental and spatial hierarchy within the river habitat and highlight the influence of multiple scales on macroinvertebrate diversity. The above suggests that both local and landscape scales must necessarily be considered for environmental management and the conservation of Andean lotic ecosystems.