Heterogeneity in altered streams does not increase the richness of stream specialist species of Odonata in the Maranhense Cerrado

The Brazilian Cerrado is a biodiversity hotspot that has suffered significant vegetation loss in the states that make up the so-called MATOPIBA region in recent years an area currently experiencing soybean cultivation expansion in Brazil. This expansion can change the environmental conditions of freshwater streams, as they receive the impacts of activities occurring in their drainage basin. In this study, we assessed how anthropogenic activities impact the conservation status and environmental heterogeneity of streams and how these modifications affect the proportion between abundance and species richness among the suborders of Odonata (Anisoptera and Zygoptera). We also assessed whether conserved streams had a greater number of specialist species when compared to altered streams. To assess these objectives, we collected data from 24 streams within matrices presenting a gradient in their integrity and vegetation cover conditions. Altered areas showed a tendency higher to heterogeneity compared to preserved streams. As expected, we observed that the proportion of abundance and species richness of Zygoptera was higher in preserved streams, while for Anisoptera, it was higher in altered streams. Despite altered sites having higher environmental heterogeneity, we failed to register of a greater number of specialist species in these areas. This implies that the presence of riparian forests is essential for maintaining habitat integrity supporting the maintenance of species that are more sensitive to changes in environmental gradients.

Implications for insect conservation: We underscore the significance of permanent protection areas in maintaining the habitat integrity of streams and preserving the diversity of Odonata species, particularly for Zygoptera.