Discriminating unifloral honey from a dioecious mass flowering tree of Brazilian seasonally dry tropical forest through pollen spectra: consequences of honeybee preference for staminate flowers

International audienceMyracrodruon urundeuva (“aroeira”) is a dioecious tree of the seasonally dry tropical forest (SDTF) of Brazil and source of a unique unifloral honey. To discriminate this honey by its pollen spectra, we compared melissopalynological analysis of reference honey samples with those of other samples collected in the SDTF belt. Reference honeys had on average 99% of aroeira pollen, while the other honey samples averaged 84% of this pollen. We used the receiver operating characteristic (ROC) curve, applied here for the first time in honey analysis, for determining the cut-off value of at least 93% of Myracrodruon pollen in a sample for classifying unifloral aroeira honey. The over-representation of aroeira pollen in this honey reflects that honeybees visited ten times as many staminate flowers as pistillate flowers. We conclude that unifloral aroeira honey has uniform pollen spectra, as a byproduct of the preference of honeybees for staminate flowers

Content of phenolic compounds in monofloral aroeira honey and in floral nectary tissue

O objetivo deste trabalho foi quantificar os compostos fenólicos totais no mel monofloral de aroeira (Astronium urundeuva) e verificar, por meio de testes histoquímicos, se estes compostos estão presentes nos tecidos florais. O apiário, com abelhas Apis mellifera, foi instalado em meio a aroeiras, na região do semiárido do estado de Minas Gerais, Brasil. A partir da anatomia das flores e da raque da inflorescência, observou-se epiderme ornamentada, tricomas tectores e glandulares, idioblastos e sistema secretor desenvolvido. O mel de aroeira apresenta, em média, 142.5±22.6 mg 100 g-1 de compostos fenólicos totais, valor considerado muito elevado quando comparado aos de outros méis monoflorais provenientes do Brasil e do mundo. Os testes histoquímicos detectaram a presença de substâncias fenólicas nos idioblastos e nos ductos secretores associados ao floema nos tecidos florais, especialmente no parênquima nectarífero, na epiderme e nos tricomas glandulares. Os compostos fenólicos estão presentes no tecido floral de ambos os morfos florais, principalmente no nectário onde as abelhas coletam o néctar. Os resultados obtidos são os primeiros, na literatura, indicativos de que os compostos fenólicos produzidos pelas árvores de aroeira são transferidos através do néctar para o mel. Este estudo contribui para o estabelecimento de padrões de qualidade do mel de aroeira e para a identificação da sua origem botânica.The objective of this work was to quantify the content of total phenolic compounds in monofloral honey from aroeira (Astronium urundeuva) trees and to verify, through histochemical tests, if these compounds are present in the floral tissues. The apiary, with Apis mellifera bees, was installed among aroeira trees in the semiarid region of the state of Minas Gerais, Brazil. From the anatomy of the flowers and of the inflorescence rachis, an ornamented epidermis, tector and glandular trichomes, idioblasts, and a developed secretory system were observed. Aroeira honey has an average phenolic content of 142.5±22.6 mg 100 g-1, a value considered very high when compared with those of other monofloral honeys from Brazil and around the world. Histochemical tests detected the presence of phenolic substances in the idioblasts and secretory ducts associated with the phloem in the floral tissues, especially in the nectar parenchyma, epidermis, and glandular trichomes. Phenolic compounds are present in the floral tissue of both floral morphs, mainly in the nectary where honeybees collect nectar. The obtained results are the first, in the literature, indicative that the phenolic compounds produced by aroeira trees are transferred through the nectar to the honey. This study contributes to the establishment of quality standards for monofloral aroeira honey and to the identification of its botanical origin

Figure 1 in Food niche of Exomalopsis (Exomalopsis) fulvofasciata Smith (Hymenoptera: Apidae) in Brazilian savannah: the importance of oil-producing plant species as pollen sources

Figure 1. Number of Exomalopsis fulvofasciata recorded on Byrsonima flowers in the two savannah areas. Ecological Station of Panga, MG (ESP) – 1 to 9 and State Park of Serra de Caldas Novas, GO (SPSCN) – 10 to18.Published as part of <i>Rabelo, Laíce Souza, Bastos, Esther Margarida Alves Ferreira & Augusto, Solange Cristina, 2016, Food niche of Exomalopsis (Exomalopsis) fulvofasciata Smith (Hymenoptera: Apidae) in Brazilian savannah: the importance of oil-producing plant species as pollen sources, pp. 1859-1873 in Journal of Natural History 50</i> on page 1864, DOI: 10.1080/00222933.2016.1169328, <a href="http://zenodo.org/record/3993335">http://zenodo.org/record/3993335</a&gt

Food niche of Exomalopsis (Exomalopsis) fulvofasciata Smith (Hymenoptera: Apidae) in Brazilian savannah: the importance of oil-producing plant species as pollen sources

Rabelo, Laíce Souza, Bastos, Esther Margarida Alves Ferreira, Augusto, Solange Cristina (2016): Food niche of Exomalopsis (Exomalopsis) fulvofasciata Smith (Hymenoptera: Apidae) in Brazilian savannah: the importance of oil-producing plant species as pollen sources. Journal of Natural History 50: 1859-1873, DOI: 10.1080/00222933.2016.1169328, URL: http://dx.doi.org/10.1080/00222933.2016.116932

Figure 5 in Food niche of Exomalopsis (Exomalopsis) fulvofasciata Smith (Hymenoptera: Apidae) in Brazilian savannah: the importance of oil-producing plant species as pollen sources

Figure 5. Abundance of pollen types according to grain size categories: small (S) and medium (M) in two natural areas. (A) Ecological Station of Panga, MG (ESP), and (B) State Park of Serra de Caldas Novas, GO (SPSCN).Published as part of <i>Rabelo, Laíce Souza, Bastos, Esther Margarida Alves Ferreira & Augusto, Solange Cristina, 2016, Food niche of Exomalopsis (Exomalopsis) fulvofasciata Smith (Hymenoptera: Apidae) in Brazilian savannah: the importance of oil-producing plant species as pollen sources, pp. 1859-1873 in Journal of Natural History 50</i> on page 1867, DOI: 10.1080/00222933.2016.1169328, <a href="http://zenodo.org/record/3993335">http://zenodo.org/record/3993335</a&gt

Figure 2 in Food niche of Exomalopsis (Exomalopsis) fulvofasciata Smith (Hymenoptera: Apidae) in Brazilian savannah: the importance of oil-producing plant species as pollen sources

Figure 2. Estimated number of pollen types in each study area using extrapolation curves. ESP: Ecological Station of Panga, MG and SPSCN: State Park of Serra de Caldas Novas, GO.Published as part of <i>Rabelo, Laíce Souza, Bastos, Esther Margarida Alves Ferreira & Augusto, Solange Cristina, 2016, Food niche of Exomalopsis (Exomalopsis) fulvofasciata Smith (Hymenoptera: Apidae) in Brazilian savannah: the importance of oil-producing plant species as pollen sources, pp. 1859-1873 in Journal of Natural History 50</i> on page 1865, DOI: 10.1080/00222933.2016.1169328, <a href="http://zenodo.org/record/3993335">http://zenodo.org/record/3993335</a&gt

Figure 4 in Food niche of Exomalopsis (Exomalopsis) fulvofasciata Smith (Hymenoptera: Apidae) in Brazilian savannah: the importance of oil-producing plant species as pollen sources

Figure 4. Abundance of pollen types according to the anther type: poricidals (P) and non-poricidals (NP). (A) Ecological Station of Panga, MG (ESP), and (B) State Park of Serra de Caldas Novas, GO (SPSCN).Published as part of Rabelo, Laíce Souza, Bastos, Esther Margarida Alves Ferreira & Augusto, Solange Cristina, 2016, Food niche of Exomalopsis (Exomalopsis) fulvofasciata Smith (Hymenoptera: Apidae) in Brazilian savannah: the importance of oil-producing plant species as pollen sources, pp. 1859-1873 in Journal of Natural History 50 on page 1867, DOI: 10.1080/00222933.2016.1169328, http://zenodo.org/record/399333