Tropical high mountain lakes show unique environmental conditions where chironomids play an important role in ecosystem functioning. The characteristics of these environments could favor diet overlap and therefore a high interspecific competition. This study described the dietary habits of chironomid genera, identified whether the dietary habits were specialized or generalist, and analyzed the diet overlap in the genera. Chironomidae larvae were collected from four lakes of the Chingaza paramo during the dry season, between April and May of 2 016. The feeding habits of larvae were evaluated by analyzing gut contents following standard methods. Each genus was assigned to trophic guilds (carnivore, detritivore and algivore) and the diet overlap was estimated using the Pinka's index. A total of 1 003 individuals were collected and nine genera were identified. Larvae consumed mainly fine particulate organic matter (FPOM), algae, macrophyte fragments, macroinvertebrates, and animal tissues. FPOM was the main feeding resource of detritivores. The analysis of diets showed a high affinity of each genus for a single trophic guild and most of the genera were generalist in the use of resources. For all lakes, high levels of diet overlap were observed among genera and trophic guilds, mainly among detritivores. Our results suggested that Chironomidae larvae of these lakes presented well differentiated trophic habits, and showed a moderate diet overlap within detritivores and carnivores.

La vegetación riparia es primordial para el funcionamiento de los ecosistemas acuáticos al aportar materia orgánica. Dado que el perifiton juega un rol indispensable en la dinámica de estos ecosistemas y existen pocos trabajos sobre su ecología en el Neotrópico, se planteó la pregunta: ¿Cómo afecta el tipo de cobertura vegetal de la zona riparia, la estructura del fitoperifiton de humedales de la Orinoquía? En noviembre de 2016 se estudiaron 15 humedales con cobertura boscosa y 15 humedales con vegetación herbácea en su zona riparia. Los humedales están ubicados en la zona periurbana de Villavicencio, Meta (Colombia). Se comparó la diversidad algal entre coberturas riparias y se realizaron análisis de Redundancia para determinar que variables ambientales explicaban la composición del fitoperifiton. Se encontraron 467 morfotipos de algas, el 36,2 % perteneció a la clase Zygnematophyceae, 35,3 % a Bacillariophyceae y 16 % a Chlorophyceae. En cuanto a las diatomeas, se encontraron 165 morfoespecies distribuidas en 30 géneros. Eunotia y Pinnularia fueron los más representativos. Los análisis multivariados indicaron que la composición de diatomeas se relacionó con la cobertura vegetal litoral y el carbono orgánico total. El resto del fitoperifiton fue explicado por la temperatura y la conductividad. Modelos de regresión lineal mostraron que la diversidad de diatomeas fue explicada por el número de sustratos, la temporalidad y la cobertura vegetal riparia. Los resultados permiten concluir que en humedales antropizados de la Orinoquía colombiana, el tipo de cobertura vegetal riparia afecta la composición y diversidad de las diatomeas.

Factors controlling phytoplankton in tropical high-mountain drinking-water reservoirsHydraulic dynamics is one of the primary factors determining the structural and temporal changes in phytoplankton communities in reservoirs. There is little information on the factors that explain the temporal changes in biotic communities in the high-mountain reservoirs that provide water to the city of Bogotá (Colombia). Our objective was to identify the environmental factors controlling the biomass and composition of algal communities in four tropical high-mountain reservoirs. We hypothesised that hydraulic dynamics is the major determining factor in temporal changes in phytoplankton communities in tropical mountain reservoirs regardless of the nutrient concentration in the system. We studied the temporal changes in phytoplankton over five years in four reservoirs that exhibit different nutrient concentrations and hydraulic management regimes. The phytoplankton in all of the reservoirs were characterised by the dominance of Dinophyceae. Canonical correspondence analyses and Pearson's correlations showed that the water renewal rate primarily explains the phytoplankton composition, followed by total nitrogen, total phosphorous and silicates. The effect of the water renewal rate was different depending on the particular conditions in each system; thus, in reservoirs with greater hydraulic dynamics, the water renewal rate explained the selection of secondary species and dominant species adapted to a broad range of environmental conditions. In the reservoir with a higher physical stability, eventual changes in the water renewal rate shifted the dominant species, reduced diversity and altered phytoplankton succession. In the reservoir with the largest volume and lowest nutrient concentration, phytoplankton species were selected primarily based on chemical and physical variables related to climatic seasonality. Our results suggest that the model for hydraulic management of the reservoirs plays an important role: in highly dynamic reservoirs, there is a direct causal relationship between phytoplankton and physical variables such as stability and water renewal rate; in less dynamic environments, phytoplankton species growth responds primarily to water chemistry.