Especificidade de habitat e morfologia como filtros para a distribuição de Odonata no cerrado Maranhense

Abstract

Odonata are hemimetabolic insects, widely used in studies of aquatic ecosystems, especially those related to anthropogenic impacts resulting from changes in land use. In order to improve their use as bioindicator organisms, we need to expand our knowledge about the responses of species to the environmental gradient, especially those that are modified by anthropic action. The study seeks to assess the relationship between habitat specificity and adult morphology of Odonata, as well as the difference in tolerance of species in different environmental conditions in the Cerrado Maranhense. The collections took place in 24 streams in the municipality of Caxias, Maranhão, from May to November 2016 and March to April 2017. We collected 824 specimens, distributed in 57 species, with 12 classified as generalists and five as specialists of intact habitat. Habitat generalists tend to be larger than species that specialize in intact environments, the length and width of the wings together with the length of the chest were the most important characteristics for this differentiation. The species Erythrodiplax fusca and Erythrodiplax basalis had the highest levels of tolerance and were classified as generalists, Telebasis griffinii and Epipleoneura williamsoni had the lowest levels of tolerance. However, specialist species from intact environments do not always have lower tolerance levels. Epipleoneura westfalli, Epipleoneura williamsoni, Telebasis coccinea, Hetaerina dutati and Argia hasemani can be used as bioindicators of intact environments, associated with preserved riparian vegetation. More than half of the species (61%; n = 35) were considered rare, something common in a very diverse community. A fact is the fragmentation of aquatic environments in the region, which has been shaping the Odonata assemblages, making room for generalist species and excluding species that need more intact conditions to survive. Understanding this balance or distribution of species is essential to establish efficient strategies to reduce anthropogenic impacts, as well as to seek to establish efficient conservation strategies that can meet the requirements of the most specialized species.