Abstract
Abstract: Aim Describe the diversity of immature stages of Odonata (Insecta) in streams from a subtropical island in southern Brazil and investigate the influence of environmental variables on the composition of their assemblages. Methods Eleven low-order streams (1st to 3rd order) were sampled in two conservation units located in the island of Santa Catarina (southern Brazil) between 2010 and 2012. Immature specimens of Odonata were collected using a Surber sampler. The influence of water abiotic parameters and habitat structure (mesohabitats: riffle vs. pool areas, microhabitats: litter vs. stone substrates) on the composition of Odonata was tested through the seasons using ordination diagrams and redundancy analysis. Results Nine odonate genera from seven families were recorded in the study region. The genera Desmogomphus, Epigomphus (Gomphidae), Heteragrion (Heteragrionidae) and Perilestes (Perilestidae) have their first records described for the state of Santa Catarina. Additionally, biological notes are provided for other odonate genera concerning substrate use. The composition of Odonata communities changed over the seasons and they were influenced by water temperature and velocity. Additionally, odonate composition differed significantly between microhabitats (substrate type) and mesohabitats (riffle vs. pool areas) in the streams studied. Conclusions The lower genera richness of Odonata recorded in the island of Santa Catarina in relation to other Brazilian subtropical streams is probably associated with the insular condition of the study region. This study also demonstrated that substrate (organic and inorganic) and mesohabitat (riffle and pool) types were important drivers of the composition of the fauna of immature odonates, evidencing the role of climate and habitat structure in influencing subtropical stream insect communities.
Highlights
The distribution of insect assemblages in lotic ecosystems is influenced by several environmental drivers
The lower genera richness of Odonata recorded in the island of Santa Catarina in relation to other Brazilian subtropical streams is probably associated with the insular condition of the study region
This study demonstrated that substrate and mesohabitat types were important drivers of the composition of the fauna of immature odonates, evidencing the role of climate and habitat structure in influencing subtropical stream insect communities
Summary
The distribution of insect assemblages in lotic ecosystems is influenced by several environmental drivers. The structure of insect assemblages is associated with the habitat structure and ecological integrity of running waters (Allan & Castillo 2007; Thorp & Covich, 2010; Mendes et al, 2017). Streams have become one of the most threatened ecosystems throughout the world, facing several kinds of impacts, such as damming, riparian vegetation removal and urban development (Allan & Castillo 2007). These processes are assumed to be prominent in island regions due to spatial delimitations (March et al, 2003; Ramírez et al, 2012). The knowledge on the ecology of stream insects from tropical and oceanic islands is far more developed than in temperate and continental ones (New, 2008; Thorp & Covich, 2010; Ramírez et al, 2012; Longo & Blanco, 2014)
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