Zonação e estratificação da fauna subterrânea de Presidente Olegário, noroeste de Minas Gerais

Abstract

There are several factors that may influence the richness and distribution in the subterranean fauna, just as resource avaiability and distribution, the local climate characteristics, the quality of the habitat and the vegetation surrounding it. Hypogean systems present high degree of endemism and their populations present as intrinsic characteristics a reduced number of individuals and are usually dependent on nutrients imported from the surface. These factors, among other results in an extremely fragile hypogean environment. This study aimed to verify the taxonomics groups that occur in Presidente Olegário caves, located at northwestern of Minas Gerais, Brazil. Along with that it aimed to verify through statistical tests as the biotics and abiotics variables influence the distribution and composition of subterranean fauna of this region. For these purposes, collections using combinated sampling methods occured in five different visiting occasions, contemplating both dry and rainy periods. The Presidente Olegário karst area presented high richness (386 species in seven caves sampled). Four new species and three new records besides four troglomorphic morphotypes were registrated. It was also verified how essential the execution of replics are, since the detection of rare species increases with the number of samplings. The caves presented high taxonomic distinctness and therefore, presented high faunistic singularity. The species distribution is positively associated to abiotics variables (temperature, relative humidity and precipitation), which can promote niche diversification when changed and consequently increase the local diversity. Therefore faunistic patterns can be changed for sazonality influence in the subterranean environment. High values of richness and abundance were registered at the entrance and twilight zones, where higher amounts of organic matter were found. The fauna stratification occurred with some taxa occurring preferentially in certain substrates types, which is probably related to food resources availability. Therefore, the terrestrials communities studied seem to be strutured based on energy resources and thus, a food web was built for these caves. Several impacts are present in Presidente Olegário, such as pasture, agriculture and future projects of gas extration and hidreletrics. Thus, this region with high richness and faunistic singularity and its area of influence should be considered as priority for conservation.