Seasonal variation in trophic interactions and niche partitioning among spider guilds associated with rupicolous bromeliads in the Brazilian Caatinga

Bromeliads are recognized as keystone structures that support complex arthropod communities, particularly in seasonally stressed environments. This study investigated how climatic seasonality shapes trophic interactions and niche partitioning among spider families associated with the rupicolous bromeliad Encholirium spectabile in the Caatinga domain. Field data were collected following a standardized protocol over eight years (2011–2018), encompassing over 5500 h of systematic diurnal and nocturnal sampling across dry and rainy seasons. We constructed both binary and abundance-weighted trophic networks, evaluated modularity, nestedness, and specialization (H′₂), and calculated Levin's index (B′) for seasonal niche breadth. We recorded 2290 spiders (19 families) and 28,860 potential prey items (19 groups). Spider families exhibited pronounced seasonal variation in abundance and resource use, with significant shifts in network topology between seasons. During the resource-limited dry season, networks showed higher specialization (H′₂ = 0.59) and nestedness (NODF = 9.62), with active hunters and web-builders forming distinct trophic modules. In the rainy season, increased prey availability led to reduced specialization (H′₂ = 0.12), lower modularity, and broader dietary overlap. Ambush predators demonstrated the widest seasonal niche breadth (B′ = 0.882), indicating a generalist, opportunistic strategy. The results demonstrate that seasonal environmental filters dynamically reorganize food-web structure and drive temporal niche partitioning among predators, highlighting the role of bromeliads as stable habitats that maintain predator-prey interactions year-round in a semi-arid ecosystem.