Spider ecology and functional traits were analysed within side bars (SB) of the middle Paraná River, investigating their relationship with environmental variables. Pitfall traps were utilized to capture spiders during four seasonal surveys spanning the years 2018 to 2019 on three SB, characterized by varying hydrological conditions. These surveys were conducted across three pre-defined zones: Wet Zone (WZ), Temporally Exposed Zone (TEZ), and Permanently Dry Zone (PDZ). The three zones were significantly differentiated according to sedimentological variables, vegetation cover, humidity, and soil organic matter (SOM). A total of 732 spiders were collected, representing 21 families and 49 species. Lycosidae and Linyphiidae were notably dominant. The species Sphecozone ignigena, Glenognatha lacteovittata, and Agalenocosa grismadoi were the most abundant. The PDZ was the most diverse zone in terms of guilds (8), species (spp) and morphospecies (msp) (34), families (18) and total abundance (295), in addition to exhibiting the greatest vegetation cover. Analysis of beta diversity of species during the rising limb of water flow revealed that replacement exceeded nesting levels in all seasons studied, indicating that most of the beta diversity was attributable to replacement. Furthermore, specific associations were observed within spider guilds. This study was a pioneer in exclusively examining the spider communities on the banks of the second longest river in South America and analysing how their ecology and functional traits behave under different environmental variables.
