Nectar production dynamics and daily pattern of pollinator visits in Brazil nut (Bertholletia excelsa Bonpl.) plantations in Central Amazon: implications for fruit production

Abstract

We investigated composition and secretion patterns of nectar in the Brazil nut tree (Bertholletia excelsa) and visitation patterns and glossa length of the main flower visitors along the anthesis, aiming to understand the implications for pollination and fruit production. Nectar sugar composition was dominated by sucrose and nectar secretion was continuous until 15:30 h, although flowers secreted, respectively, almost 50 and 80% of the total nectar volume and solutes in the hours immediately following flower opening, which coincides with peak flower visitation by bees. We observed a total of 19 bee species visiting the flowers to collect nectar throughout the day that can be considered pollinators. The three most abundant bee species were Xylocopa frontalis, Eufriesea flaviventris, and Eulaema mocsaryi that accounted for about 90% of the visits. In open flowers, nectar was generally scarce, encouraging bees to move among trees, and likely increasing xenogamous pollen transfer in natural habitats. However, in the large-scale Brazil nut tree plantation studied here, where genetically identical (clone) individuals are planted together in high densities, even where bees move between trees, they seem to promote functional geitonogamy, determining pollen limitation.