Effects of Environmental Variables and Habitat Integrity on the Structure of the Aquatic Insect Communities of Streams in the Cerrado-Caatinga Ecotone in Northeastern Brazil

Abstract

Alterations in the environmental gradients of streams have a direct influence on the structure of the insect communities of the orders Ephemeroptera, Plecoptera, and Trichoptera (EPT), which are extremely sensitive to changes in habitat. The present study evaluated how habitat integrity in streams influence the composition of EPT genera, by testing three hypotheses: (i) the composition of the EPT genera is modified along the gradient of environmental disturbance; (ii) the composition of the EPT genera is more homogeneous in gradients with a higher degree of anthropogenic disturbance, and (iii) the greatest degree of environmental disturbance along the gradient results in the reduction of the richness and abundance of EPT genera. The study focused on 14 tributaries of the middle Itapecuru River, within an area of ecotone between the Brazilian Cerrado and Caatinga biomes. Data on the structure and physicochemical traits of the streams were collected between September 2014 and July 2015, a period that covers both the dry and rainy seasons in the study region. The results of the present study indicate that the composition of the EPT genera is modified in accordance with the variation in the habitat integrity, although, in contrast with expectations, more impacted areas had a more heterogeneous composition than undisturbed ones. The areas with more integrated landscapes contribute positively to the richness and abundance of EPT genera of the streams of the Cerrado-Caatinga ecotone. Given this, habitat integrity provide an important predictor of EPT diversity in the streams of the Cerrado-Caatinga ecotone.

Agriculture affects functional diversity of aquatic insects in Subtropical Atlantic Forest streams

“…Thus, we can see that changes in streams adjacent areas (e.g., land use) are important environmental predictors in the structuring of aquatic insect communities. Thus, it is expected that changes in land use in the stream drainage area will affect the limnological water quality and, consequently, the aquatic biota (Breda et al, 2020;Castro et al, 2021). In this study, we observed that the vegetation removal was decisive for the change in limnological variables such as water temperature, pH, and dissolved oxygen.…”