Use of the Zygoptera/Anisoptera Ratio (Insecta: Odonata) for Habitat Alteration Assessment in Cerrado Streams

Natural landscapes of Latin America, such as the Cerrado biome, are increasingly changing due to conflicting development models between economic growth and biodiversity conservation. In cases of total or partial suppression of natural vegetation, more sunlight reaches the streams, leading to changes in Odonata assemblages. Due to their thermoregulation characteristics, the proportion of the suborder Anisoptera tends to increase whereas the suborder Zygoptera will decrease, as this suborder is more sensitive to habitat loss. We assessed whether the proportions of individuals and species richness of Zygoptera and Anisoptera changed due to environmental quality loss in Cerrado stream habitats. Also, we assessed the performance of ratios using genus and family level. We conducted our study at 18 streams in Mato Grosso State, Brazil. We sampled Odonata communities and measured the environmental quality of each stream using the Habitat Integrity Index. To assess the relationship between the environmental quality of the streams and the Odonata ratios, we performed generalized linear models with the beta distribution family. The models showed that the loss of environmental integrity caused Zygoptera to decrease and Anisoptera to increase. In addition, we found that Acanthagrion/Zygoptera and Argia/Zygoptera ratios showed a strong relationship with habitat integrity, being plausible alternatives for use in monitoring programs. We conclude that the Zygoptera/Anisoptera ratio is a good indicator of environmental quality for the Cerrado biome and therefore makes for a suitable tool for citizen science programs in which no taxonomic expertise is required.