Influência de fatores ambientais na distribuição das formas imaturas de odonata (Insecta) em um trecho do Riacho Marambaia, Ilha da Marambaia, RJ

Abstract

The Odonata of Ilha da Marambaia, located in South Coast of Rio de Janeiro State had been studied of taxonomy privileged and data about ecology are insufficient. The objective of this work was to increase the knowledge about the immature of Odonata and to check the distribution pattern with the influence of environmental factors on this. The study was carried out in a stretch of the Marambaia stream, monthly from September 2003 through August 2004, with D-net, bolter, surber and tweezes, in four sites (P1, P2, P3 and P4), with 100 m each. Before each sample, the physicochemical variables were measured, the meteorological data was obtained by Meteorological Station of Ilha Guaíba/RJ and physical variables of the environment were determinate by eye. The biotic and abiotic data were correlated by correspondence analysis (CCA) and multi regression to check the most influence variable on the immature distribution. The sites were compared by clustering and principal coordinate analyses. A total of 1.859 immatures of Odonata distributed in 08 families and 26 genera were collected during this study. The seasonality varied between genera and sites. In the two years of this study, P4 (upper site) had more richness (19 genera), principally Anisoptera and a less individual number collected. The P1 (lower site) had the least richness (10) and the higher number of Zygoptera. Four families were more abundant Coenagrionidae, Megapodagrionidae, Gomphidae and Libellulidae. In the assessment of the influence of the environmental variables in these families distribution stand out: dissolved oxygen to Coenagrionidae (P1 and P4) and Megapodagrionidae (P1); pH to Coenagrionidae (P3) and Gomphidae (P2); rainy to Coenagrionidae (P2), Gomphidae (P3) and Megapodagrionidae (P2); and DQO to Libellulidae (P4). In P4 the more important factor that influenced the presence of Libellulidae genera was the physical environment (habitats temporary). The CCA indicated the lower association of genera Argia, Heteragrion, Brechmorhoga e Macrothemis with the sites. The clustering and principal coordinate analyses indicate the association between P1 and P2 (upper sites) and P3 and P4 (lower sites) confirmed the environmental similarity and the proximity. The association by genera was P1, P2 e P3 and P4 isolated. This distance between P4 and the other site confirm the diference of community composition. These results demonstrate the diversity of Marambaia stream immature community and the importance of the environmental factors variation on the distribution of them in the region.