Abstract
Abstract: Aim The present study tested the hypothesis that the composition of the odonate assemblages in environments with greater habitat integrity is significantly different from that of areas with reduced habitat integrity. Methods The samples were collected between April 2017 and November 2017 in eight streams in Caxias, in the Brazilian state of Maranhão. The habitat integrity index was used to quantify habitat integrity. The odonate specimens were collected by the fixed area scanning method. Results The habitat integrity index ranged from 0.265 to 0.915 at the different localities. A total of 229 specimens were collected, representing 19 odonate species. Species composition varied among streams that presented different degrees of conservation, with some species being typical of specific habitats. However, this variation had no effect on the number of taxa or the abundance of odonates, which may reflect the local substitution of extinct specialist species by generalists. Conclusions Evidence indicates that the reduction of habitat integrity is an important predictor of changes in the biodiversity of aquatic insects in streams such as those of the Cerrado-Caatinga ecotone.
Highlights
In the tropics, the decrease in habitat integrity is an important driver of changes in the environmental quality of river basins, and this variable is correlated with the riparian forest loss (Veras et al, 2019; Carvalho et al, 2013a; Nessimian et al, 2008)
The HII scores of the study streams ranged from 0.265 to 0.915, the preserved streams, with higher HII values, present riparian forest with continuous forest composed of native trees and few breaks in the riverside area
The environmental integrity of the stream did not affect the species richness or abundance of odonates, there was a clear influence on species composition, with degraded and conserved streams being clearly separated
Summary
The decrease in habitat integrity is an important driver of changes in the environmental quality of river basins, and this variable is correlated with the riparian forest loss (Veras et al, 2019; Carvalho et al, 2013a; Nessimian et al, 2008). Human activities that reduce or alter riparian forests and modify the physical structure of the habitat have a direct influence on the species richness and composition of a number of different groups of organisms (Cabette et al, 2017; Cunha & Juen, 2017; Oliveira-Junior et al, 2017; Correa et al, 2015) In this context, the use of sentinel organisms or bioindicators of environmental quality (Ghannem et al, 2018; Shaiek et al, 2018; Galindo-Pérez et al, 2017), such as insects of the order Odonata, is essential for the assessment of environmental impacts and the prioritization of conservation areas (Miguel et al, 2017; Nóbrega & De Marco Junior, 2011). Anisoptera and Zygoptera are very useful as bioindicators, assessing the impact of habitat degradation on aquatic fauna (De Marco Junior et al, 2015; Miguel et al, 2017)
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