When stability defies harshness: terrestrial invertebrate community persistence in a large subterranean hotspot in the Brazilian semi-arid region

Abstract Although caves are generally considered more environmentally stable than surface ecosystems, their biological communities do not invariably exhibit temporal constancy. The influence of seasonality on species richness and community composition in subterranean systems remains poorly understood, particularly in Neotropical regions. Changes in rainfall, temperature, humidity, and epigean productivity may alter cave microhabitat conditions, potentially affecting the abundance, composition, richness, and niche occupancy of terrestrial invertebrates. To test this hypothesis, we investigated Brejões I Cave, a large cave system located in the Brazilian semi-arid region. Twenty-four fixed sectors were surveyed during wet and dry periods, with concurrent measurements of microclimatic conditions, habitat structure, and resource availability. Seasonal changes in terrestrial invertebrate community composition were quantified using the Temporal Beta-diversity Index (TBI), while species’ niche dynamics were assessed using the Outlying Mean Index (OMI) and Within Outlying Mean Index (WitOMI). Contrary to expectations, no significant seasonal differences were detected in species turnover, richness, or abundance, indicating seasonal stability in community structure. Although only a small subset of species responded to environmental gradients, WitOMI analyses revealed seasonal shifts in subniche breadth, mainly characterized by niche contractions during the dry season and occasional expansions in some taxa. These patterns were associated with reductions in temperature and humidity. Overall, our results indicate that climatic fluctuations can influence species-level niche dynamics without altering overall community structure in large, environmentally buffered cave systems.