Determinantes da estrutura da rede de interação planta visitante floral: padrões de interação e influência de atributos das espécies

Abstract

Mutual interaction networks among plants and floral visitors provide information on the ecological dynamics, and coevolutionary processes that shape interactions among species. Knowing the adjacent processes that predict the patterns of interactions among species, remains one of the challenges in studies of mutualistic networks. The objectives of this thesis were: 1) to evaluate the influence of sociality of visitors in the network topology; 2) to evaluate how the biotic and abiotic variation affect the topological structure of the network, and 3) which are the possible impacts of two exotic species interactions on the native communities. In order to do this, the plant and the floral visitors communities were sampled for twelve months in a patch of Cerrado in southeastern Brazil. For data analysis, we used concepts of the field of ecological network and modeling. For the first objective, it was observed that sociality caused changes in the network topology. However, some proprieties did not show significant differences among the networks. Future understanding of these processes will be elucidated by studies that take into account other aspects of species biology, which are not normally considered in network studies, such as the dependence upon floral resources on different species development periods, and the patterns of visitors foraging. For the second objective, it was observed that the floral visitors abundance is the most important variable associated with the network metrics, and that the abiotic factors act indirectly, influencing on the phenology of pants (resource availability), and in the floral visitors activity, which translate into pattern of interactions among species. With the use of visitors sociality, and the abiotic variables, our results offer an advance in the understanding of multiple factors and their combination as determinants of structure of the mutualistic networks. For the third objective, it was observed that the interaction among invasive species cause alteration in the native communities that, in turn, affect the patterns of interaction among species, which resulted in an increase in the visitation rate of the exotic visitor. On the other hand, it was observed that de native plant diversity has a negative impact on the visitation rate of the exotic visitor. These results attest evidence for the invasive meltdown hypothesis to the increased and accelerated impact of biological invasion rate, and that the communities with greater diversity of species are proportionally more resistant to these invasions.