Habitat specificity and morphology-main filters for the distribution of Odonata in the Cerrado Maranhense, Brazil

Odonata is amphibian insects, widely used in studies of aquatic ecosystems. In order for us to improve their use as bioindicator organisms, there is a need to increase our knowledge of how species distribution responds to the environmental gradient. Our study evaluates the relationship among habitat specificity, morphology and differences in spatial niche breadth of Odonata, in streams with different environmental conditions in the Cerrado Maranhense. We collected in 24 streams between May and November 2016 and March and April 2017. A total of 824 specimens were collected, distributed in 57 species, of which 12 were classified as generalists and five as specialists in integral habitat. Habitat generalists tend to be larger than species that specialize in intact environments; PERMANOVA showed a significant separation between the generalist and specialist groups in environments with less anthropic impact (Pseudo F = 0.173; p = 0.001). The length and width of the wings along with the length of the chest were the most important characteristics for this differentiation. Telebasis griffinii and Epipleoneura williamsoni (OMI – 0.0 and 5.0) presented the lowest spatial niche values. However, specialist species did not always show the lowest values. More than half of the species in our study ( n = 35) were considered rare by the Multinomial species classification method (CLAM) for having an abundance of less than seven individuals. The number of rare species is a matter of concern given the fragmentation of the region's aquatic environments, which has been shaping Odonata assemblages, making room for generalist species and excluding species that need more complete conditions.