RESUMEN Las Podostemaceae son importantes componentes de las mallas tróficas de los ambientes reófilos pero su importancia como hábitat para los invertebrados es poco conocida. En este estudio se analizó la variación temporal de la abundancia y riqueza de taxa de los macroinvertebrados asociados a Podostemum distichum y Podostemum muelleri (Malpighiales: Podostemaceae) en dos arroyos de bajo orden durante diferentes estaciones del año. La abundancia total promedio difirió entre fechas de muestreo, pero no entre arroyos. Se registraron 14 familias de macroinvertebrados distribuidas en 9 órdenes en ambos arroyos. El Análisis de Escalamiento Multidimensional No Métrico (NMDS) reflejó también diferencias en el patrón estacional. Tanto el coeficiente de similitud como el de complementariedad, indican que ambos arroyos fueron muy similares en cuanto a la composición de las familias de macroinvertebrados. Las especies de Podostemaceae dominantes en cada arroyo constituyen hábitats de diversidad intermedia de acuerdo al índice de diversidad utilizado.
We evaluated the influence of the horizontal flows of the Paraná River on the composition and distribution of the floodplain landscape and we defined the ecohydrological signature of some species-index in the low Paraná River section, (27° 38' 04" S and 58° 50' 46" W). During the drought phase, the structure of the vegetation were characterizad using a Cottam & Curtis method. The trees were positioned in the topographic gradients during the flood phase, taking as reference the river water sheet in the nearest hydrometric gauge. To obtain the pulse attributes in different positions of the geomorphological gradient, PULSO software was used considering the daily water levels at Corrientes city between 1985 and 2015. Two main types of flooded forests were identified: pionner forest, dominated by one or two species (Salix humboldtiana, Tessaria integrifolia) in recent bars and islands, and pluri-specific flooded forests (Albizia inundata, Cecropia pachystachya, Croton urucurana, Inga uruguensis, Ocotea diospyrifolia, Nectandra angustifolia and Peltophorum dubium) occupying bars of the highest islands, with shorter flood phases, with trees are distributed in 2-3 strata in a closed canopy. Pulses were more frequent in pioneer forests than in multispecific forests. The ecohydrological signature allows the optimum condition and distribution limits of each species to be established. It is a tool to know the adjustment of biotic elements (populations) to the river variability regime. The procedure used can be used to anticipate the possible reorganization of the river plain landscape as a result of flow variations predicted by climate change models.
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