Chemical Characterisation of the Floral Oil of the Murici (Byrsonima sericea): Discovering the Constituents Used in Reproduction by Oil-Collecting Bees

The recent decline in population of generalist bees such as those of the genera Apis and Bombus has shown the need to breed and manage a larger number of bee species. Among the species with potential use for agricultural pollination in the Neotropics, a peculiar small group has specialised in collecting floral oil. Therefore, the aim of this study was to analyse the chemical profile and to identify the main constituents of the floral oil of the nance (Byrsonima sericea), an abundant species in the Northeast of Brazil and widely used by oil-collecting bees. A sample of 400 flowers of the nance were collected between October 2017 and January 2018. The samples were derivatised (MSTFA) and analysed by gas chromatography-mass spectrometry in a Model 7890B GC Gas Chromatograph System coupled to a Model 5977A MSD mass spectrometer. The compounds were separated using an HP-5ms capillary column and identified by comparing the mass spectra with the National Institute of Standards and Technology (NIST) database, and by comparison of the retention indices (RI). From the chromatographic analysis, it was possible to identify 23 constituents, especially fatty acids and carboxylic acids. The results indicate the presence of tricosanoic acid, palmitic acid and heneicosanoic acid as the main constituents of the oil under study. There is still a need for studies that would better explain the relationship of these constituents with the bees that use the oil.

The role of floral oils in the evolution of apid bees (Hymenoptera: Apidae)

Most bees collect pollen and nectar for their larvae, while some also collect other resources. We investigated the evolution of floral oil-collecting behaviour in the Apidae and the evolutionary effects of floral oils on host brood cells for cuckoo bees. Focusing on apid bee phylogeny, we reconstructed the evolution of floral oil collection by females, use of floral oils in cell construction and the inclusion of oils in provisioning immatures. Ancestral character reconstruction demonstrates that floral oil-collecting behaviour arose four times independently. We also found that in cuckoo bees, parasitization of oil-collecting bees arose three times (including one secondary return) in Apidae. Except for Ctenoplectrina, oil cuckoo bees are all closely related to each other, forming an independent clade within the Nomadinae. Analysis of evolutionary transition rates indicates that there is a greater tendency for switching from an oil-collecting host to a non-oil-collecting host than the reverse. In apid bees, evolutionary transition rates are higher for switching to cuckoo behaviour from an ancestral lineage in which females collect floral oils than from other pollen-collecting lineages. We conclude that adaptation to oil collection is advantageous for pollen-collecting bees, and that the origin of oil cuckoo bees from non-oil cuckoo bees is constrained.

Paleocene origin of the Neotropical lineage of cleptoparasitc bees Ericrocidini-Rhathymini (Hymenoptera, Apidae)

Cleptoparasitic bees abandoned the pollen collecting for their offspring and lay their eggs on other bees’ provisioned nests. Also known as cuckoo bees they belong to several lineages, especially diverse in Apinae. We focused on a lineage of Apinae cleptoparasitic bees, the clade Ericrocidini+Rhathymini, which attack nests of the oil-collecting bees. We sequenced five genes for a broad sampling in this clade plus a large outgroup and reconstruct phylogeny and divergence times. We confirmed the monophyly of the clade Ericrocidini+Rhathymini and its position inside the ericrocidine line, together with the tribes Protepeolini, Isepeolini and Coelioxoidini. Our results corroborate the current taxonomic classification. Ericrocis is the basal most lineage in Ericrocidini and the position of Acanthopus and the most diverse genus Mesoplia were inconclusive. Ericrocidini+Rhathymini diverged from Parepeolus aterrimus 74 mya in the Cretaceous. Considering the robust molecular evidence of their sister relationships, the striking differences on the first instar larvae morphology of the two groups are probably adaptations to the distinct nesting biology of their hosts. As other parasites in the ericrocidine line, both groups possess larvae adapted to kill the immature host and to feed on floral oil provisioned by the host female. The evolution of host specialization in the line Ericrocidini+Rhathymini retroced to the Eocene when they arose synchronously with their hosts, Centris and Epicharis.

The Similar Usage of a Common Key Resource Does Not Determine Similar Responses by Species in A Community of Oil-collecting Bees

Variations in abundance and species richness among communities are often determined by interactions between biotic and abiotic factors. However, for communities composed of species that share a common specialization (such as similar foraging adaptations) it may be a key ecological factor involved in the common specialization that affects community variations. To evaluate this possibility, we characterized the guild of oil-collecting bees of a Neotropical savanna in Brazil and tested whether differences in Byrsonima abundance and availability of floral oil explain differences in species richness and abundance of oil-collecting bees of different tribes. Both the number of species and total abundance of Centridini species increased with the abundance of Byrsonima. One plausible explanation for the stronger adjustment between the abundance of Centridini and Byrsonima is that the abundance of these plants affects not only the availability of floral oil, but also of pollen. These findings indicate that the existence of a common specialization among different species does not homogenize their response to variations in a common explored resource.

Pterandric Acid – its Isolation, Synthesis and Stereochemistry

Some plant families have a specialized type of pollination system, with floral lipid rewards for pollinators, which is common. In neotropical Malpighiaceae species like Pterandra pyroidea, this specialized type of pollination system is apparently shifting from floral oils/lipids to pollen reward. Mass spectrometric analysis (GC/MS-EI) indicated that P. pyroidea floral oil has a unique chemical composition, i.e., few fatty acid constituents possessing acetoxy groups at positions 5 and 7, which is distinct from the other floral oils of sympatric Malpighiaceae species. The structure of the major floral oil constituent, a novel fatty acid, a nti-5,7-diacetoxydocosanoic acid, was confirmed based on synthesis, mass fragmentation, and 1H and 13C NMR analyses; the compound is herein named pterandric acid.

Floral-oil-producing Plantaginaceae species: geographical distribution, pollinator rewards and interactions with oil-collecting bees

Floral oils as reward to pollinators occur in eleven plant families and appeared at least 28 times in the evolutionary history of flowering plants. They are produced in epithelial or tricomatic glands and collected by oil bee visitors. The present paper focuses on floral-oil-producing species of Plantaginaceae, a Neotropical group namely Angelonia clade. This group comprises around 40 described species in the genera Angelonia, Basistemon, Monttea, Monopera and the oil-less Melosperma. We present a revision of all species of the Angelonia clade, their geographical distribution, resources offered to pollinators and records of flower visitors, especially oil-collecting bees. These plants rely only on oil-collecting species in the tribe Centridini and Tapinotaspidini for a successful pollination, being the interaction between both partners an especial case of bee/flower adaptation in Neotropical region. Some bee species depend only on the oil of Plantaginaceae flowers to survive, while others can collect on several floral oil sources. The pollinating bees explore the oil glands located in sacs using specialized hairs in the forelegs. With this study, we hope to inspire further research relating to this fascinating group of plants, in which most species are rare and occur in highly endangered habitats in South American open vegetation biomes.