Composição da fauna aquática subterrânea da área cárstica do Alto Ribeira: implicações ecológicas e para a conservação

Abstract

The composition of aquatic subterranean fauna is influenced by different factors, such as evolutionary history, habitat heterogeneity, environmental gradients, interspecific interactions, and species dispersion. The present study was carried out in the karst area of Alto Ribeira, state of São Paulo, Brazil, in caves located at the Parque Estadual Turístico do Alto Ribeira (PETAR) and its surroundings. Despite the implementation of the conservation unit, not all caves are protected, as catchment basins, caves and part of subterranean systems are located outside the park boundaries. Moreover, some of its caves have impacts caused by local tourism and water contamination. Thereby, this study intended to understand the composition and distribution of subterranean aquatic fauna of the Alto Ribeira karst area. The first chapter aimed to compare the distribution and composition of the community in cave streams belonging to the three sub-basins of the Alto Ribeira (Iporanga, Betari and Pilões streams); to verify the distribution of fauna in relation to abiotic characteristics and the contribution of components of beta diversity (turnover and nestedness) to the dissimilarity of cave communities. The composition of the communities differed between caves in the different sub-basins and between caves in the same sub-basin, as many endemic species and/or species with restricted distribution were found. Communities from different caves were influenced by different physical and chemical variables, according to the ecological characteristics of each species. The dissimilarity between the studied cave communities was mainly due to turnover, which is influenced by ecological, hydrogeological, and historical factors. In the second chapter, the composition of fauna in different aquatic habitats (drips, puddles, and streams) present in the caves was investigated and the sampling sufficiency of systematic samplings performed over different annual cycles was verified. In addition, it was verified whether the richness of the aquatic fauna is related to the extension of the caves and to the phylogenetic diversity. Unique species were found in different types of habitats. The occurrence of rare and endemic species is common in caves and, therefore, it was not possible to access the total richness even after five samplings. Larger caves did not have higher richness, which is influenced by other factors (such as availability of resources, influence of abiotic variables and historical factors). The caves that had the highest phylogenetic diversity are those with more troglobites (i.e., animals restricted to the subterranean environment) or phylogenetically distinct non-troglobic taxa, and not those with higher species richness. The third and last chapter aimed to determine the fragility degree of the aquatic and terrestrial fauna from PETAR caves and their surroundings, in order to propose management and conservation strategies. The fauna of all the caves studied had maximum or high fragility, according to criteria that took into account species richness, occurrence of species with restricted distribution, new species, troglobitic species and/or species in threatened fauna lists, and in the case of aquatic fauna, indicator species of good quality water. The fragility of this fauna associated with the occurrence of rare and endemic species, and the high dissimilarity and the high taxonomic distinctness observed in the caves studied, reinforces the importance of maintaining the caves within conservation units and protecting their entire area of influence, expanding the PETAR boundaries. In addition, management strategies must be implemented, such as restricting the walk of visitors in the caves, monitoring fauna, inspection activities, and environmental and patrimonial education. These actions are necessary because impacts on the caves and their area of influence can lead to the loss of this unique biodiversity.