Ecologia de invertebrados em novo hotspot de biodiversidade subterrânea na América do Sul

Abstract

Subterranean ecosystems play a fundamental role in sustaining life on Earth and are therefore extremely important to humans, as they provide a wide range of ecosystem services. Despite their importance, they remain among the least explored environments in the world, with significant knowledge gaps. Their defining characteristics, permanent absence of light, climatic stability, and limited resource availability, make them excellent models for ecological and evolutionary studies, as these conditions strongly shape both species and communities. In this context, we investigated a large and extensive cave system in northeastern Brazil, the Brejões Cave System. Although this system is highly relevant for paleontological and geological studies, its biota has been scarcely studied. In this dissertation, we conducted a systematic inventory of the invertebrate fauna to understand how the community is structured across spatial and seasonal scales. Additionally, we examined the seasonal dynamics of an endangered freshwater sponge species endemic to Brejões I cave, Racekiela cavernicola Volkmer-Ribeiro, Bichuette & Machado, 2010. Our results indicate that the Brejões system harbors a high diversity of invertebrate taxa, including several species new to science and even new genera. The system also supports at least 23 strictly cave-dwelling species (troglobionts), positioning it as the sixth subterranean biodiversity hotspot (i.e., caves or cave systems with more than 20 troglobiont species) identified in South America. We further found that microclimate, resource availability, and shelter availability are key factors structuring the spatial organization of the invertebrate community in Brejões. Contrary to our expectations, given that these caves have large entrances and are therefore subject to greater seasonal variation, similar to the epigean environment of the Caatinga domain, the community remained stable in terms of abundance, species richness, and composition between the rainy and dry seasons, although shifts in niche occupation were observed for some species. The freshwater sponge Racekiela cavernicola was one such species, showing higher abundance during the dry season, with its distribution primarily influenced by temperature, pH, and conductivity. Our findings provide important information for the management of this system, which is already located within the Gruta dos Brejões/Veredas do Romão Gramacho Environmental Protection Area, yet remains vulnerable to impacts such as heavy metal pollution and climate change. Therefore, long-term studies are essential for the conservation of the Brejões Cave System