Community structure of Neotropical wetland insects in Northern Venezuela. I. Temporal and environmental factors

Abstract

Abstract: The temporal distribution of aquatic insects in relation to habitat conditions was assessedin some northern VenezuelanN eotropical wetlands. The hypothesis that abiotic and biotic factors interacting in time may simultaneously explain the community structure of aquatic organisms was evaluated. Larval insects were sampled over a one-year period in five wetland types; 13 variables were quantified to describe each habitat. Partial redundancy analysis was used on insect abundance data to partition the variance into four components: a) pure environmental variation without seasonal effect, b) seasonal variation of environmental factors, c) pure temporal factors (months), and d) unexplained variation. Our results showed that pure and temporallystructured environmental factors (a + b) explained between 30 % and 58 % of the variation of insect abundances within wetlands, whereas pure temporal factors also significantly contributed 13 % - 29 % to variation in taxa abundance. Physical factors (rainfall and water depth), wetland trophic state (phytoplankton), and water chemistry (mainly CO2 and alkalinity) were significantly associated to community structure variability. We hypothesize that the interplay of trophic conditions, related chemical conditions, wetland duration, and insect life history patterns, all of which are mediated by seasonal fluctuation in rainfall, could largely account for the temporal distribution of the insect taxa in these wetlands.