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Plant-pollinator interactions constitute complex mutualistic relationships responsible for the maintenance of the reproduction of flowering plants in different biomes. The genus Centris stands out as one of the main groups of pollinators in the Neotropical region. These bees have a close relationship with floral oil-producing plants, using this resource in the construction of their nests and/or larval feeding. The aim of the present study was to compare the resources exploited by Centris perforator and Centris xanthomelaena and assess the established trophic relationships of these two species in a fragment of dry forest (Caatinga domain). For such, direct observations were made at the flowers and analyses were performed of the pollen load on the body of female bees and the content of the larval provisions in the nests. A strong association was found between the two bee species and plants with poricidal anthers of the genus Chamaecrista, which accounted for more than half of the larval diet in both species. Samples of the pollen load of C. xanthomelaena exhibited a greater diversity of pollen types. While Rhaphiodon echinus was a constant source of nectar for C. xanthomelaena, C. perforator females collected nectar from plants of short, rapid flowering, such as Cenostigma microphyllum and Tabebuia aurea. Malpighia emarginata was the main source of floral oil for both species. However, C. xanthomelaena also interacted with Angelonia cornigera and Krameria sp. to obtain this resource. The similarity in the trophic niche of the species was 57% in the subsamples of pollen on the body of females and 46% for larval provision. The results showed that areas of native vegetation are essential for bee populations in regions with agricultural activity, ensuring a regular supply of ecological resources for these bees.

Abstract The study investigated native solitary bee species that nest in pre-existing cavities in the Baturité Massif, State of Ceará, Brazil, their preference for nest substrates and aspects of these bee communities. Samples were taken in four distinct areas of the Baturité Massif using three types of trap-nests: dried bamboo internodes, cardboard tubes and rational boxes. Out of the 185 nests offered, 34 were colonized and 24 of them produced 131 bees, belonging to two families (Apidae and Megachilidae) and five genera (Centris, Mesocheira, Euglossa, Megachile and Coelioxys) from six species, including parasitic ones. Nesting preference was observed to certain types of substrates (χ²=17.89, p

Floral scent is an important component of the trait repertoire of flowering plants, which is used to attract and manipulate pollinators. Despite advances during the last decades about the chemicals released by flowers, there is still a large gap in our understanding of chemical communication between flowering plants and their pollinators. We analyzed floral scents of guarana (Paullinia cupana, Sapindaceae), an economically important plant of the Amazon, using chemical analytical approaches, and determined the attractiveness of the scent to its nocturnal bee pollinators using behavioral assays in the field. Pollen loads of attracted bees were also analyzed. Inflorescences of guarana emit strong scents, both during day and at night, with some semi-quantitative differences between day- and night-time scents. Synthetic scent mixtures containing some of the identified floral scent components, including the most abundant ones, i.e., linalool and (E)-β-ocimene, successfully attracted the nocturnal Megalopta bee pollinators. Pollen analyses revealed that many of the attracted bees had pollen grains from previous visits to guarana flowers on their bodies. Overall, our data show that guarana flowers attract nocturnal bee visitors by their strong scents and suggest that the chemical communication between this plant and its pollinators is a key component in crop production of this economically important plant species.