Composition, abundance and diversity of immature Odonata (INSECTA) insects living in stretches of middle Araguari River, Amapá State, Amazonian Region, Brazil

Abstract

Odonata order, popularly known as dragonflies, comprises insects belonging to group Palaeoptera and presents hemimetabolous development encompassing three life cycle stages: eggs, larvae and adults. Odonata order has three suborders, namely: Anisoptera, Zygoptera and Anisozygoptera - the last one is exclusively distributed in Asia. The aim of the current study is to investigate the composition, abundance and diversity of Odonata larvae in middle Araguari River (Amapá, Brazil) by evaluating space-seasonal fluctuations and their association with different substrates. Eight collection sites were set along the river. Quarterly samplings were performed within an annual cycle (April/2018 to April/2019) by positioning a trawl "D" net (Rapiché) on the riverbed and scraping the substrate to collect 2L of sample. Odonata richness, abundance and diversity indices were evaluated. Data were statistically treated based on simple descriptive analysis, means, medians and standard deviations, Kruskal-Wallis test (nonparametric data) and ANOVA (parametric data) in the R-statistics Software. Two hundred and ninety-seven (297) individuals were identified; Libellulidae was the most abundant family (80.13%). Diversity and equitability have shown variations between sampling sites (p<0.05) and collection campaigns (p<0.05). Only abundance was influenced by categorical variables such as downstream/upstream river and substrate type. Higher taxonomic resolution, in combination to environmental variables, could help establishing ecosystem relationships that were not identified in the current study.