Seasonal and vertical distribution of Araneae in an area with predominance of Attalea phalerata MART. (Arecaceae), in the Pantanal of Poconé, Mato Grosso, Brazil

This study was carried out in an "acuri" formation, an area with predominance of Attalea phalerata MART. (Arecaceae), located at the Retiro Novo farm, Pantanal of Mato Grosso. This was done in order to analyze the temporal and spatial distribution of spiders and the species composition, structure and distribution of the litter/soil-dwelling spider community, and to evaluate the influence the flood pulse renders on it. The results are compared with data on canopy spider communities, obtained by canopy fogging. The sampling was done using "WINKLER" extractors during the four extreme abiotic periods in the northern Pantanal: low-water (terrestrial phase), high-water (aquatic phase), dry season (with no rain) and rainy season. During each of the four periods 10 quadratic plots of 1 m2 each were selected for sampling, first litter and then the uppermost 5 cm soil layer, totaling 40 m2 sampled area. Altogether, 343 individuals of spiders (8.6 ± 1.1 ind./m2) from 16 families were obtained. Zodariidae (182 ind.; 53.1 % of the total catch) and Oonopidae (62 ind.; 18.1 %) were most abundant. Ten guilds were differentiated, separated in hunters and weavers, with predominance of nocturnal soil runners. Many different groups of spiders appeared to share the same habitat. Seasonality was strongly marked with highest abundance during low-water (138 ind.; 40.2 % of the total catch) and low abundance during high-water (26 ind.; 7.6 %). Comparing these results with canopy fogging data revealed distinct stratification of the spider fauna. From a total of 24 families obtained from both canopy and litter/soil, only 11 were shared between both habitats. Best sampling success in both investigated habitats was during periods of low humidity