Abelhas polinizadoras da castanheira-do-brasil (Bertholletia excelsa) cultivada na Amazônia central: papel do néctar e do entorno do plantio na polinização da cultura

Abstract

The low productivity observed in commercial crops of Brazil nut trees (Bertholletia excelsa) may be associated with the management of cropping systems, interfering decisively in diversity, richness and abundance of pollinating bees and foraging behavior. However, in cultures of Brazil nut, so little is known about the effect of the landscape in the community of bees flowers visitors and the interactions between the resources offered by the plant and their interaction with their pollinators. Thus, this project aims to understand the role of nectar in pollination of Brazil nut trees and study the effect of the surrounding planting systems on the visitation of potential pollinators to Bertholletia excelsa under cultivation in central Amazonia rain forest. The experiment was conducted between the months of October to December 2009 and 2010 in an area of 3600ha of farming the Brazil nut tree (Bertholletia excelsa), belonging to Agricultural Aruanã, located in Itacoatiara, Amazonas state. The results showed that the flowers of B. excelsa already proffer nectar from anthesis (14.48 μl, 38.74% and 6.56 mg of sugar), with a pattern of secretion volume and the amount of sugar continued and increasing until 15:30 h and 13:30 h, respectively, increasing rates of 2.10 / hour and 0.69 mg / hour. After these times, for each variable, there was a reduction in the rate of secretion, featuring early resorption process. In contrast, the concentration of solute concentration was decreasing after 7:30 h while maintaining similar values (p> 0.01) throughout the morning and afternoon superior to, coincident with the peak activity of the bees. Despite the pattern of nectar secretion show higher values of volume and amount of sugar in the afternoon, under natural conditions of visitation of the study area almost all the nectar was collected in the morning yet, due to the high activity of visitors influenced by conditions temperature. All flower visitors sampled except Megachile sp., Have characteristics of size glossa meets morphological structure of flowers, providing success in collecting nectar and potentially in the pollination process of chestnut. The area with a population capoeira remained abundant and richer than capoeira without (p <0.05), showing the importance of this natural vegetation as a repository for maintaining species of pollinating bees inside the planting of chestnut. The species Xylocopa frontalis and Eufriesea flaviventris stood out as the most abundant, the first being found in greater quantity in cultivation with poultry (88% of total bees) and the second in the area without poultry (64%). However, the distance from the trees to the fragments of native vegetation did not affect the abundance and diversity of bees floral visitors (p> 0.05), both in the environment and in poultry without the roost, despite having been checked several populations in this environment. Thus, we conclude that there seems to be a synchronism between the pattern of nectar secretion and activity of floral visitors and potential pollinators, increasing the chances of reproductive success by bee-plant interactions. We can also conclude that the system of land management that keeps tracks of secondary vegetation "capoeira" inside the plant maintains a greater richness and abundance of pollinating bees, thereby increasing pollination and yield of the crop.