Insetos aquáticos em ambientes subterrâneos: estrutura e dinâmica temporal das comunidades

Abstract

Caves are unique systems, being under the constant threat of anthropogenic impacts. However, in order to propose appropriate management and conservation actions for cave biological integrity preservation, it is crucial to understand community structure, diversity patterns and temporal dynamics. However, little is known about caves` ecological process and patterns, speccialy considering aquatic communities associated to cave streams. Thus, the main objectives of this thesis were to understand cave aquatic insect communities structure; determine communities dynamics patterns; investigate experimental disturbances effects over cave benthic communities and evaluate how changes in diversity components could be related to flow changes, as well as on functional feeding groups. Therefore, we investigated three subterranean allogeneic streams, located in Minas Gerais, Brazil, over one year.The first manuscript shows that each subterranean stream is structured in a unique way, and those factors that exhibited greater variation, were the most important in determining distributional species patterns. In addition, each stream has an unique set of fauna, mainly determined by the regional species pool of the upstream drainage. Finally, it was verified the importance of shelter availability in the streams for aquatic insects and their role in determining the highest values of richness. Our findings reveal that common impacts in the caves’ surroundings, such as deforestation and mining, can severely affect the associated cave streams communities. The second manuscript aimed to understand the importance of flood pulses, determining the highest temporal beta diversity values. Moreover, it was possible to infer that temporal changes in the bottom substrates from the subterranean channel lead to major changes in species composition. In addition, it was found a pattern of high community instability, with constant colonization and species extinctions. Thus, it was attributed to subterranean allogeneic streams the characteristic of hyperdynamic systems. In addition, changes in communities caused by experimental disturbances were comparable to natural dynamics of cave systems.Finally, we found that the highest contribution of aquatic insects to the gamma diversity was determined by the beta diversity, given by differences among caves. In addition, temporal variations of diversity components are negatively influenced by high flow events. Thus, higher flow rates, were responsible for homogenizing subterranean aquatic communities. The same pattern was found when considering functional feeding groups. However, predators did not have relations with flow changes. Such organisms have greater mobility, hence its distribution pattern is more closely related to prey density effects, than to flow changes.Results are used to discuss the effects of the channel homogenization resulting from deforestation and mining to cave communities. In addition, our results are also useful to infer appropriate tourist routes in cave systems that have allogeneic hyperdynamic streams. Finally, we discuss the importance of including studies on diversity spatial components, in order to promote knowledge for determining the actual influence area from the surface environment on the caves communities.