Distúrbios antrópicos alteram as propriedades das redes de interações foréticas em florestas tropicais

Abstract

Tropical forests have undergone intense environmental degradation in recent decades. Selective logging and the fire are among the main threats, especially to Amazonian forests. It is therefore necessary to understand the ecological consequences of these environmental disturbances for developing effective conservation strategies that prevent or mitigate the degradation impacts on biodiversity. The use of interaction networks to assess ecological responses to different human activities may contribute to a more holistic view of the problem, whereas the species can interact, both obligatory or facultatively, each other to distinct purposes. Phoresy is an commensal interaction poorly studied in the context of environmental disturbances, but that may have important implications for the conservation of species and ecosystem functions. Until now, no study in tropical forests has evaluated how networks based on phoretic interactions respond to environmental disturbances. This work addresses this knowledge by investigating changes in network properties based on interactions between phoretic mites and dung beetles sampled within disturbed Amazonian forests. The first part of the dissertation comprises a general introduction and a literature review. The second consists of a paper which aimed to evaluate changes in the interaction networks properties sampled across a disturbance gradient including undisturbed forests, logged forests and burned forests in the Tapajós National Forest, Belterra - PA. Dung beetles were collected in three areas of each forest system using pitfall traps baited with a mixture of pig and human dung. After sampling, each individual was carefully inspected and the associated phoretic mites were removed. Then, interactions matrices were built and used for the analyses. The main finding of this study was that network metrics significantly changed along the gradient of forest disturbance but no significant differences were found in total species richness of phoretic mites and dung beetles between systems. In general, there was a decrease in network complexity (links per species and Shannon‘s diversity of interactions) and in the specialization of interactions along the increasing gradient of disturbance. However, the network nestedness and compartmentalization presented an opposite tendency, with the burned forests exhibiting the highest values. This research was the first to evaluate changes in the properties of the phoretic networks in tropical forests. This research may support more effective strategies for biodiversity conservation, indicating that efforts should be focused not only species, but also in interactions networks between groups associated to ecosystem functioning.