Óptimo ecológico y tolerancia ambiental de macroinvertebrados bénticos y su distribución en cuatro regiones de Colombia

Introduction: Tolerance and distribution of benthic macroinvertebrates along environmental gradients are key elements for understanding how communities respond to changes in water quality and for developing robust bioindication schemes. Objectives: To evaluate the tolerance of benthic macroinvertebrates in four regions of Colombia (Andean, Caribbean, Pacific, and Orinoquian) to identify ecoregional bioindicators of water quality. Methods: We compiled environmental and biological datasets from fluvial systems monitored between 2015 and 2023, including 10 environmental variables and 132 taxa. Dominant environmental gradients were identified using Canonical Correspondence Analysis (CCA) or Redundancy Analysis (RDA), depending on the response pattern of the biological data. Ecological optima and environmental tolerance ranges for each taxon were estimated using the Weighted Averaging method. A cluster analysis was then applied to assess patterns of ecoregional affinity based on optima and tolerance values of taxa shared among ecoregions. Results: Macroinvertebrate distributions were structured mainly by gradients in oxygen availability, nutrient enrichment, conductivity, suspended solids, and organic matter, with distinct patterns among ecoregions. Although several taxa were shared among ecoregions, they exhibited contrasting optima and tolerance values, indicating context‑dependent ecological responses. The analysis revealed greater ecological similarity between the Andean and Orinoquian ecoregions, whereas the Pacific ecoregion was clearly differentiated by its highly dynamic hydrological and physicochemical conditions. Taxa with high optima and narrow tolerance ranges emerged as key ecoregional bioindicators (four in the Andes, eight in the Caribbean, six in the Pacific, and five in the Orinoquian region). Conclusions: This approach shows that bioindication based on ecological optima and environmental tolerance must be interpreted at the ecoregional level, thereby improving the development of precise and comparable biomonitoring schemes in neotropical lotic ecosystems.