Padrões espaço-temporais de substituição de espécies em assembleias de formigas de solo (Hymenoptera: Formicidae) em uma hidrelétrica na Bacia Amazônica.

Abstract

Assemblages and communities vary naturally throughout time and space. However, hydroelectric power plant constructions and the fact that they are still seen as the best way to the growing energy demand are a big threat to animals’ communities within and on the areas that are influenced by those constructions. Therefore, it is important to monitor animals’ and plants’ communities within those areas. Ants are one of the most abundant insects’ groups and are sensitive to environmental changes, being excellent ecological models. In this study, we analyzed the influence of the Santo Antônio hydroelectric plant reservoir filling on the spatiotemporal patterns of species turnover and directionality of ant assemblages over 10 monitoring campaigns from 2011 to 2014. To sample the ant fauna, Winkler extractor were used in 24 250m plots, located in four 4km modules installed at different distances from the Madeira River. During the monitoring, 37,969 ants were sampled, divided in 47 genera and 206 species and morphospecies. The species turnover was dynamic throughout time. Before the reservoir filling, an average of 50,3% of ants were substituted, while during the filling, 44,8% and post-filling, 49,3%. During the reservoir filling, an expressive decay in the species substitution happened, reaching 38,2%, homogenizing the assemblages. However, this process was rapidly reverted on the beginning of the post-filling phase, when turnover values returned to ones observed before. Along with the species substitution decay, there was a significant directional change in assemblages’ composition throughout the monitoring. As environmental variables (e.g. altitude, clay content and terrain slope) are considerably stable in the area, the filling process was the strongest factor influencing on the species turnover on ants’ assemblages also over space, in all different modules. In addition, there was not significant difference on the species substitution at different distances from the margin, strengthen the importance of the filling process on the species substitution. The high ant’s assemblages’ resilience allowed a recover in the rate of species’ substitution to happen. Thus, it is important to emphasize the importance of analyzing the communities’ directionality throughout time in studies that take into account the substitution of species in areas that are influenced by disturbances, such as in hydroelectric areas. In addition, the combination of these analyses with the spatiotemporal pattern of species substitution within these communities allows a better understanding of the dynamics and what are the effects on the substitution of species in these conditions.