DOI: 10.5281/zenodo.17965396
title: Drying has limited effects on the composition of invertebrate communities across a river network of the arid Bolivian Andes

description: This dataset consists of an Excel file with two sheets. The first sheet contains environmental data and invertebrate abundance data, while the second sheet provides explanations for each column. Specifically, the environmental variables recorded in the first sheet are described in the second sheet. ‘N/A’ (not applicable) indicates missing information in environmental variables or metadata, which may vary depending on whether the data were not collected or were lost.
description: Drying River Networks (DRNs) are dominant components of global river systems, yet their ecological dynamics remain poorly documented in high-altitude tropical regions. In the arid Andes, stream communities face multiple interacting natural stressors that may pre-select taxa tolerant to additional hydrological stress. This study examines how flow intermittence shapes local (α) and regional (β) diversity, community composition and metacommunity assembly in an arid Andean DRN. 




We sampled 22 sites along the upper Chico River Basin (Bolivia) across six hydrological periods encompassing flowing, drying, dry and rewetting periods. At each site we quantified aquatic macroinvertebrate richness, abundance, taxonomic composition (%EPT, %OCH, %Diptera) and trait-based indices, together with environmental and spatial variables. Flow intermittence was expressed as the proportion of zero-flow months. We used linear regression models and β-diversity partitioning to evaluate local and regional responses, while Mantel tests assessed temporal shifts in the relative influence of environmental filtering and spatial processes.




Total richness and abundance declined significantly with increasing flow intermittence, whereas compositional and trait-based metrics did not respond to intermittence. Despite this absence of compositional change along a gradient of flow intermittence, macroinvertebrates showed consistent but moderate compositional changes across hydrological periods: the relative abundance of EPT taxa declined during dry periods while that of Diptera increased and %OCH remained comparatively stable. Spatial β-diversity was high before drying, decreased through the dry periods and rebounded during rewetting, with turnover dominating over nestedness through all periods. Environmental filtering was strongest during dry periods, whereas dispersal processes became more influential during drying and rewetting periods, indicating a temporally shifting balance.




In this arid and harsh environment, flow intermittence strongly impacts local communities, primarily reducing richness and total abundance, but without consistently altering species composition in terms of relative abundance or resistance traits occurrence.  Unlike findings from other biomes, where drying often reshapes community composition, in the arid tropical Andes, drying reduced richness and abundance but did not alter functional composition of species, suggesting that co-tolerance and functional redundancy could be  common mechanisms to face multiple and interacting natural stressors in harsh riverine environments.