Diversidade e distribuição espacial de espécies de borrachudos (Diptera: simulliidae) na bacia hidrográfica do Rio Ijuí, RS, Brasil

Abstract

The goal of this study was to determinate the diversity and spatial distribution of species of black flies in different biotypes of the Ijuí river (regions: high, medium, low), especially in the rural area. There were collected immature forms of black flies (larva and pupa) in vegetation substrate and stone swindle, in thirteen cities, during the 2015 year. In each sample were obtained temperature values, electrical conductivity, dissolved oxygen, atmospheric pressure, pH, altitude, arroyo broadness, ciliary foreit broadness. It was developed a linear correlation study between these measures and the main identified species, as well as tests of variance analysis, tukey and kruskal-wallis among three sections of the Ijuí River. The results indicated ten species of Simulium genus, being Simulium pertinax (61,3%), Simulium incrustarum (26,5%) and Simulium orbitale (4,8%) the most frequent. The first two are influenced by high and intermediary standard of organic pollution in water, respectively. It was collected a greater number of individual in the low region of the basin (47,3%), but the test showed that there is not a significant difference between the population density of the species and the different section of the Ijuí River basin. Considering the substrates, there was a greater occurrence in the vegetation (80,6%) compared to the stone swindle (19,4%). The developed analysis pointed the influence of some factors about the species as well: temperature (Simulium pertinax and Simulium orbitale), dissolved oxygen (Simulium orbitale), electrical conductivity (Simulium orbitale) and pH (Simulium incrustatum). However, the greater part of the fauna composition to the Ijuí River basin occurred according to the organic contribution resulting of the animal manure. Then, it is important to recognize that the anthropic activity is a factor which contributes significantly in the population composition of these species, as well in biodiversity reduction. In this context, the associate programs to the black flies control may elaborate actions aimed to the integrity biological preservation of the ecosystems, as well the maintenance of the water quality.