Cave spider trophic dynamics, network structure and competition: cave zone, taxonomy and bat presence drive hypogean interactions

Cave ecosystems are shaped by unique environmental constraints, influencing species distributions and trophic interactions. Spiders are often the dominant predators in caves, but their diet is restricted by local parameters that likely intensify competition and other intraguild interactions, including the confinement of energy flows to detrital and chemoautotrophic pathways. The hypogean environment also filters biodiversity with the progression from cave entrances to complete darkness, further restricting predators' trophic niches, possibly driving dietary specialization and forming truncated, incomplete food webs. Hypogean ecological networks, however, remain scarcely studied, limiting our understanding of the trophic dynamics of these systems. Here, we explore the dietary interactions of cave-dwelling spiders across 13 caves in the Levant through the integration of dietary metabarcoding, network analyses and multivariate modelling. Spider diets varied between spider families, spider cave affinities (troglophile vs. troglobite), cave ecological zones (entrance, twilight, dark), and caves with and without bats. Spider diets did not simply reflect prey availability in each cave, with some abundant prey absent from spider guts, while rare prey in caves were detected in many spider’s guts. The presence of bat colonies in the caves acted as a primary ecological driver, relating to distinct prey assemblages. We identified complex intraguild spider interactions in caves, with a notable reduction in potential exploitation competition at cave dark zones, suggesting that niche partitioning facilitates coexistence of spiders in these energy-limited underground environments. This study enhances our understanding of spiders as key predators of subterranean habitats and the unique structure of cave food webs.