Pollinator efficiency in openly grown eggplants: can non-vibrating bees produce high-quality fruits?

In the face of the global decline in pollinator populations, studies that serve as a basis for the conservation and management of crop pollinators are crucial. The eggplant (Solanum melongena) is a widely cultivated autogamous crop, whose production is favoured by pollination by vibrating (buzz pollinating bees). To our knowledge, thus far, no studies have tested for the pollination efficiency of non-vibrating bees, nor have any been conducted in semi-arid regions, or evaluated the influence of pollination on the chemical characteristics of the fruits. Here, we evaluated the influence of pollination by vibrating and non-vibrating pollinators on eggplant fruit set and fruit traits in two plantations within the semi-arid region of NE Brazil. We conducted 120 h of focal observations and compared the fruit set and size (weight, length, and basal and apical diameters) under different pollination treatments (open pollination, spontaneous self-pollination, hand-cross pollination and single visits by different species of pollinating bees). Nine visiting bee species were recorded, which differed in visiting frequency and behaviour, as well as in pollination efficiency. Although being autogamous, plants visited by the vibrating bee Xylocopa sp. set more fruits than open, spontaneous self- and cross-pollination. However, the fruits produced by Xylocopa sp. were lighter and smaller than those obtained through open pollination, highlighting the importance of multiple pollinator visits or pollinator diversity. Non-vibrating pollinators contributed to fruit production quantity and quality. Fruits resulting from open, hand cross-pollination and both vibrating (Euglossa sp. 1) and non-vibrating bees (Paratrigona sp.) were larger than those resulting from spontaneous self-pollination. Pollination treatments had no influence on fruit chemical properties. Our results highlight the importance of pollination to eggplant production and the benefits of both vibrating and non-vibrating pollinators.