Environmental variables affect the diversity of adult damselflies (Odonata: Zygoptera) in western amazonia

Abstract

Our study evaluated the effects of environmental variables on the assemblages of the sub-order Zygoptera, and tested the hypothesis that environmental variables are more important determi-nants of the structure of these assemblages than limnological variables in streams. We sampled 17 streams in the Carajás National Forest and tested our hypothesis using a linear regression analysis, with the zygopteran species composition, richness, and abundance as the response variables. Our findings indicate that both limnological and physical variables influence, independently, the characteristics of the zygopteran assemblages. The riparian forest maintains the stability of the environment and provides dispersal corridors, along which the zygopterans can reach alternative, suitable environments. The small scale of this study also implies that the continuity of the vegetation is es-sential for the dispersal of the zygopterans among different landscapes. The high levels of abundance recorded in the better-preserved environments may reflect the maintenance of specific habitats and resource availability. Riparian forest is crucial to the ecological equilibrium of the stream systems, although further research at a broader spatial scale that focuses on a greater diversity of variables should provide more robust insights into the phenomenon.