HYMENOPTERA IN RIPARIAN VEGETATION

Hymenoptera are among the dominant insects in terrestrial ecosystems, in number of species, number of individuals and even biomass. They perform vital ecological functions for ecosystems, such as pollination and natural biological control. The present study aimed to discuss the use of Hymenoptera fauna as a bioindicator of environmental quality in areas with different percentages of riparian vegetation. To this end, insect gatherings were carried out between November and December 2016, by installing Malaise traps in riparian zones of 12 streams, located in the Alto Uruguai region, in Rio Grande do Sul, with different percentages of vegetation. These were classified into natural, intermediate and impacted riparian zones. A total of 1,363 Hymenoptera were collected, belonging to 22 families. Ichneumonidae, Braconidae and Vespidae were the most representative families. The natural riparian zones had greater abundance and greater richness (709 specimens and 20 families, respectively). Meanwhile, in the impacted riparian zones, only 206 specimens belonging to 10 families were collected. ANOVA showed that abundance and richness differed significantly between riparian zones. Pearson's Linear Correlation showed that the percentage of vegetation in the drainage area is correlated with the abundance and richness of families. Redundancy Analysis indicated that Braconidae and Vespidae were influenced by the percentage of vegetation in the drainage area. The results of this study indicate that the percentage of vegetation in the drainage area affects the abundance and richness of the Hymenoptera fauna, showing that this group is an important bioindicator of environmental integrity.