Space-state experiment
We used an experimental design based on the space-state concept. A space-state design follows the dynamics of a variable of interest during a fractioned period of time (Pedersen et al. 2011). A relevant point for this method is that the current condition of the variable is bound to its past condition. Changes in the variable after the beginning of the experiment may be addressed to assess the experimental modifications. The parameters permanence and colonization of the genera were our variables of interest.
We used artificial substrates (AS) with standardized area, weight and volume. Each substrate was composed of washed river pebbles and eight leaves of Tapirira guianensis Aubl. (Anacardiaceae), a common plant in the region, with a standardized leaf area of 25.63cm2, all packed within a 500cm3(10cm x 10cm x 5cm) rectangular wire mold. The use of AS is efficient for experiments of aquatic insect colonization in Cerrado streams and constitutes a well delimited sample unit (Carvalho and Uieda 2006, Godoy et al. 2016). We used a 0.225 mm hand sieve when sampling the ASs and fixed the samples in 80% ethanol. The organisms were identified to the highest possible taxonomic resolution (genus level or family) (Wiggins 1977, Trivinho-Strixino and Strixino 1995, Pes et al. 2005, Manzo 2005, Oliveira 2006, InĂªs et al. 2007, Merritt et al. 2008, Manzo and Archangelsky 2008).