Duration: outubro/2014 a maio/2018
Funded by: FAPESB
The understanding of the structure of plant-pollinator interaction networks has benefited from the development of new analytical techniques and software in the last decades. The central role of some functional groups on the topology of these networks is one of the ecological aspects of greater theoretical and practical interest in the management (of habitats or species) and conservation of pollination services. The Meliponini social bees are a group of central importance in the pollination process in tropical environments, given their numerical dominance in ecological communities and the generalist behavior of floral resources, which led to the formulation of hypotheses in the 1990s about the central role in the malleability of flower-bee relations in the tropics with the supposed appropriation of niche spaces of other floral visitors. Although their populated colonies with a perennial life cycle lead to generalist behavior, many species may exhibit temporary preferences, concentrating the exploitation of nectar and pollen on some floral sources, often more productive (abundant and concentrated in space-time, as species with Mass flowering, for example). It is intended to understand how general behavior (which extends the possibilities of choice), associated with the process of “temporary specialization” (which leads to the manifestation of ecological preference), characteristic of Meliponini, introduce dynamics to the topological structure of the networks of bees-flowers at the level of the ecological communities where these bees are dominant. Our basic hypothesis assumes that the smaller the supply of “productive” floral sources, the more diffuse the influence of the Meliponini bees on flower-pollinator networks, which must then present dynamics dependent on the period of the year (seasonality and floristic structure of habitats). The spatial dynamics of networks between heterogeneous habitats in the landscape scale of the Três Flores National Forest (FLONA) in the state of Santa Catarina will be analyzed. The structure of the networks at the level of the ecological communities will be evaluated with two independent and complementary data sets: samples of bees in the flowers and analysis of the pollen foraging by colonies of a focal species of Meliponini (Melipona marginata). For sampling in the flowers, in each habitat, 6 sampling points were distributed, distant 150 m or more between them, where collection areas were delimited in the flowers with 500m x 20m (1ha). Three of the most distant sampling points were selected and Melipona marginata (Meliponini) colonies were arranged in the center to record the foraging activity and pollen sampling. The intensity of pollen collection in the different floral sources will be estimated with the identification and counting of the pollen grains on slides. In this case, we will apply a new technique of pollen analysis to express the results in terms of “floral equivalents”, bypassing the lack of relationship between quantity (on plates) and pollen biomass consumed. It will be elaborated an adjacency matrix with binary values of presence and absence of interaction between the groups, to perform the following calculations: size, connectivity and degree of nesting of the network. The interaction networks in the flowers will be adjusted with the pollen forage data to check effects of floral preferences in Meliponini. Next, the influence of the Meliponini on the network topology will be tested through the manipulation of the empirical data.