Habitat selection of cave-restricted fauna in a new hotspot of subterranean biodiversity in neotropics

Abstract

Environmental stability and oligotrophy are considered the main drivers of species distribution within caves due to physiological and nutritional requirements presented by many cave dwellers. However, such patterns are poorly evaluated in tropical caves, especially with regard to habitat selection and interspecific competition between invertebrate groups. Considering that troglobitic species are usually highly specialized, presenting specific requirements for environmental conditions, we hypothesize that troglobitic species will be preferentially associated with deeper areas inside the cave. These areas are stable and present trophic and physical constraints, which may favors the troglobites in competitive interactions with non-troglobitic species. The study carried out in the Águas Claras Cave System revealed a new hotspot of subterranean biodiversity, represented by 30 cave-restricted species (29 invertebrates and 1 fish species), being 73.3% terrestrial, 16.7% amphibian, and 10% aquatic. The richness of troglobitic species did not respond to physical attributes or resources availability as postulated, but increased with temperature, humidity content and with non-troglobitic species richness. The similarity of the troglobitic species along the cave was determined by the moisture content. Furthermore, the richness of troglobites was higher in those areas with greatest taxonomic distinctness of non-troglobitic species and higher values of the TB/nTB species richness ratio. The habitats requirements of the troglobitic species were not coincident, thus indicating that such species avoid niche overlapping. We highlighted the studied cave system as a singular subterranean habitat that contributes to both local and regional biodiversity. Additionally, the condition of high temperature and humidity seems to be key factors that are favoring the existence of a high number of endemic species. Unfortunately, this cave system is devoid of any official protection, thus deserving urgent actions to ensure its conservation.