Abstract
This study was carried out in headwater streams in the Paraguay and Paraná river basins, with bi-monthly samples from January to November 2004, aiming to quantify the influence of environmental factors on the temporal rate of turnover in species composition of the fish communities. The environmental variables explained 73.5% of the variation in beta diversity and 52.5% of the variation in mean dissimilarity. Altitude was the only environmental descriptor that significantly explained the variation in beta diversity and mean dissimilarity in both basins.
Highlights
Populations and communities are temporally variable, and understanding the causes and consequences of this variation is the goal of community ecology (COOK et al, 2004)
We found no significant influence of hydrographic basin on the turnover rate in species composition for TRjaccard, or for TRbeta
Of the environmental variables analyzed, only altitude significantly explained the turnover rate in species composition (TRjaccard and TRbeta). Both basins showed equivalent rates of temporal changes in species composition (Table 1 and Figure 2) and elevation is the only turnover rate descriptor, where streams located at higher altitudes have communities less susceptible to temporal variations in species composition (Figure 3)
Summary
Populations and communities are temporally variable, and understanding the causes and consequences of this variation is the goal of community ecology (COOK et al, 2004). The analysis of variation in richness and species composition over an area or time period has been an important component for studies in communities. The meta-community concept proposes that local communities are linked by species migration (WILSON, 1992), and local and regional characteristics interact to define their characteristics (RICKLEFS, 1987). The analysis of the influence of regional processes on the structure of ecological communities has emphasized the importance of spatial and temporal turnover in diversity and species composition and their contribution to regional diversity. Biological communities have high turnover rates, which are usually associated with the migration as a result of changes in resource availability, environment, and reproductive migration.
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