Distribution of the Odonata assemblages along an environmental gradient in the streams of the legal Amazonia region in western Maranhão (Brazil)

Understanding the distribution patterns of biodiversity is a pivotal challenge in ecology, exacerbated by the escalating frequency of anthropogenic events with severe consequences. This urgency underscores the need for comprehensive investigations, as exemplified by our study, which focuses on evaluating the effects of environmental and spatial variables on Odonata distribution across a gradient of vegetation cover in the eastern Amazonia landscape. In our investigation, we aimed to test the hypothesis that the distribution pattern of species in the suborder Zygoptera is significantly different from that of species in the suborder Anisoptera, considering that the environment is a more important factor for Zygoptera. Sampling was conducted across 27 streams within a landscape altered by various human activities, resulting in changes to riparian forests, sediment influx, and bank destabilization. Environmental alterations were quantified using the Habitat Integrity Index (HII) in conjunction with water’s physical-chemical variables. We register 29 Odonata species/morphospecies, reflecting a significant biodiversity. Our hypothesis regarding the differing distribution patterns of species from the Odonata suborders Anisoptera and Zygoptera due to their ecophysiological distinctions was confirmed. This underscores that environmental and spatial factors serve as the primary determinants shaping the structure of Zygoptera suborder assemblages, given that the studied streams harbored environments that greatly impede the dispersal of species within this suborder. This study contributes valuable insights into the interplay between environmental changes induced by land use alterations and the resulting impacts on Odonata biodiversity in the Amazonian landscape.