Responses of Dragonflies (Odonata) to Habitat Integrity and Environmental Heterogeneity in Amazonian Streams: lessons for conservation

Rapid landscape transformation in the Amazon, driven by human activities such as deforestation and intensive land use, has deeply affected the conservation of their aquatic ecosystems, especially small forest streams (i.e. “igarapés”). These environments rely heavily on riparian vegetation to maintain the physical and chemical conditions that support biodiversity. Among the many threatened aquatic organisms, insects of the order Odonata stand out as sensitive bioindicators of habitat alteration. We here evaluated the effects of environmental variables on the distribution of adult Odonata species in streams of the Eastern Amazon. We expected more intact streams to harbor higher Zygoptera richness, whereas less intact streams would show higher Anisoptera richness. We sampled 30 streams along a gradient of environmental alteration. We found that better-preserved streams were also better at preserving Zygoptera diversity while more degraded environments were dominated by tolerant Anisoptera as predicted. However, Anisoptera richness did not significantly increase in low-HII streams, although their relative abundance was higher there, suggesting a more pronounced species turnover than diversity loss. In addition, limnological variables, such as electrical conductivity and coarse particulate detritus, played central roles in structuring communities. These results demonstrate the efficiency of adult Odonata as bioindicators of environmental change and reinforce their use as an effective tool for their conservation and assessing environmental quality in Amazonian streams.