Efeito de fatores ambientais e espaciais na dinâmica limnológica e na estrutura de comunidades de peixes em uma planície sazonalmente alagável

Abstract

Wetlands are among the most diverse and threatened natural systems worldwide. It is thus critical to understand their spatiotemporal dynamics in order to improve management and conservation practices regarding these habitats. Analytical frameworks that allow quantifying the relative contribution of local and regional factors have improved our understanding on how wetland fish communities are organized, however little is known regarding the limnological properties of temporary aquatic habitats. In the first chapter was evaluated the relative importance of these factors for water temperature, dissolved oxygen, conductivity and pH in the Pantanal floodplains during the wet seasons of the 2006/2007. Our results showed that local processes (e.g., depth and water temperature) were more important in the beginning of the rainy season whereas regional factors had a greater contribution during the flood peak, when all aquatic habitats were highly connected across the landscape. In a similar venue, was analyzed on the following chapter what was the most important factors accounting for several properties (biomass, standard length, density, diversity and evenness) of fish communities dwelling in the same habitats. Using data from these temporary aquatic habitats spanning five years (2006, 2008, 2009, 2010 and 2011), was reported that habitat connectivity and vegetation cover explained most of the variation in the diversity, biomass and standard length of large-bodied fishes (> 50 mm) while water depth was the most important factor accounting for the diversity of small-size fishes (< 50 mm). Finally, in the third chapter, was applied the Elements of Metacommunity Structure (EMS) framework in order to evaluate the spatiotemporal dynamics of these fish assemblages during four consecutive months of the 2009 rainy season. Significant changes in the distributional patterns along the season were detected. In the beginning of the flood, when habitat patches are less connected, the fish metacommunity structure followed a nested and a quasi-nested pattern (January and February, respectively). During the following two months, when the landscape is completely flooded and habitats are more connected, the fish distributional pattern changed for a quasi-Clementsian distribution. The relative contribution of environmental, spatial and connectivity factors was also evaluated, through variation partitioning analysis. This analysis showed that the environment explain a constant fraction of the variation in species distribution during the entire season, the connectivity factors are more important in the beginning of the wet season whereas spatial factors become significant only from the mid to the end of the rainy season.