Levantamento de larvas de Odonata (Insecta) em poças de áreas serranas dos Campos Sulinos no Rio Grande do Sul

Abstract

The Odonata larvae are strongly related to the habitat characteristics of the habitats in which they live and are therefore affected by environmental changes, especially anthropic changes. Grasslands of Rio Grande do Sul comprise grassland areas of Pampa and Atlantic Forest biomes, together constituting the Campos Sulinos biome. These areas are extremely important because of their high diversity, low biological knowledge due they have been historically neglected and may have been historically neglected and face strong agricultural market pressure. Therefore, the purpose of this study was to perform an inventory of Odonata larvae in ponds in the mountainous regions of Campos Sulinos biome in Rio Grande do Sul state, as well as to analyze the spatial distribution of larvae among three mountainous areas. Sampling was carried out in the three mountainous areas of Rio Grande do Sul: Planalto Meridional, Planalto Sul-Riograndense and Planalto da Campanha. The collections were carried out between September and December 2011 and 2012, in natural and artificial ponds, temporary and permanent, using a long cable handle, with a 3mm² metallic mesh net. The larvae were identified at the level of genus used specific keys. The odonatofauna of larvae in ponds of mountainous areas of grasslands of Rio Grande do Sul presented a relatively low diversity, characterized by 17 genera. The genera Erythrodiplax, Lestes, Orthemis, Rhionaeschna and Oxyagron were dominant and widely distributed, whereas the genera Coryphaeschna, Oligoclada, Tauriphila, Acantagrion, Remartinia and Gynacantha presented low abundance and restricted distribution. The relatively low richness recorded may be related to the fact that many ponds in grasslands are temporary, especially in higher areas such as plateaus, where shallow soil and more rugged relief do not favor the occurrence of deep natural ponds. There was no difference in the richness or assemblage structure between the three plateaus studied. These results show that local environmental factors, such as hydroperiod, predator pressure and aquatic vegetation, were probably more important than regional characteristics, such as geomorphological formation, climatic variation and physiognomy in structuring larval assemblages of Odonata. In this way, the composition, richness and spatial structure of the odonatofauna of ponds of mountainous areas in Rio Grande do Sul seem to be strongly determined by local factors related to the characteristics of the ponds to the detriment of regional factors.