Distribuição espacial e temporal de simuliidae (Diptera: Culicomorpha) em uma bacia hidrográfica do bioma Pampa, no Sul do Brasil

Abstract

The immature stages (eggs, larvae and pupae) of the Simuliidae (Diptera) develop in the water streams and the adult females of certain species have hematophagous habit, with many species of veterinary and medical importance. The information on the bioecology of this group of flies is still insufficient for the Neotropical region. In Brazil, the main researches are basically restricted to the Central Amazonia and the Atlantic Forest. In this context, the aim of the present study was to know the diversity and distribution patterns of the simulids in basin of the Piratinim river, located mostly in the Pampa biome, in the Rio Grande do Sul, Brazil. Immature stages of Simuliidae were collected in six streams, with three sampling sections in each, totalizing 18 sampling points. Furthermore, abiotic variables were obtained at the sampling sites, considering two seasons of the year (Spring, acocording to literature and Autumn, for comparison) and different spatial scales: basin regions (source/spring, intermediate and mouth) and stretches sections of streams (nascent, medium and estuary). Data analysis mainly included techniques of multivariate statistics, such as correspondence analysis and canonical correspondence analysis. The results showed the occurrence of nine simulids species for the region: Simulium pertinax, S. orbitale, S. incrustatum, S. jujuyense, S. subpallidum, S. inaequale, S. perflavum, S. lutzianum e S. travassosi, with the first three being the most abundant (45.62%, 22.61%, and 18.17%, respectively). The mean species number per stream was 4.78 (±1,31). It was possible to verify that the community structure was mainly influenced by the local factors (streams stretches), but also by those in a larger scale (basin regions), although in a less significant way. The majority of the species displayed homogeneous distribution in environments, with exception to the S. orbitale and S. jujuyense that were recorded mainly in stretches of the estuary and S. pertinax in stretches of nascent. As regarding the region, S. pertinax was less present in the mouth region. In relation to the environmental variables, an increase in water width and temperature towards the estuary was observed. Hence, the data has important and unpublished information about the community of these insects in the Pampa biome, founding the good state of the basin conservation and preservation and may be useful for the state program of control of Simulídeos of Rio Grande do Sul. However, it is important to execute more studies, covering other biomes and many locations, allowing the results comparison.