Contrasting patterns of foraging behavior in neotropical stingless bees using pollen and honey metabarcoding

Abstract

Stingless bees are major flower visitors in the tropics, but their foraging preferences and behavior are still poorly understood. Studying stingless bee interactions with angiosperms is methodologically challenging due to the high tropical plant diversity and inaccessibility of upper canopy flowers in forested habitats. Pollen DNA metabarcoding offers an opportunity of assessing floral visitation efficiently and was applied here to understand stingless bee floral resources spectra and foraging behavior. We analyzed pollen and honey from nests of three distantly related stingless bee species, with different body size and social behavior: Melipona rufiventris, Scaptotrigona postica and Tetragonisca angustula. Simultaneously, we evaluate the local floristic components through seventeen rapid botanical surveys conducted at different distances from the nests. We discovered a broad set of explored floral sources, with 46.3 plant species per bee species in honey samples and 53.67 in pollen samples. Plant families Myrtaceae, Asteraceae, Euphorbiaceae, Melastomataceae and Malpighiaceae dominated the records, indicating stingless bee preferences for abundant resources that flowers of these families provide in the region. Results also reinforce the preference of stingless bees for forest trees, even if only available at long distances. Our high-resolution results encourage future bee-plant studies using pollen and honey metabarcoding in hyper-diverse tropical environments.

Figure 1

Map of the IBGE reserve and surroundings showing the location where bee nests were installed and the locations of Rapid Botanical Surveys. The image also shows main vegetational types, i.e. cerrado savanna, riverine forests, swamps, cultivated and urban areas. Photographs depict a. cerrado savanna vegetation type (Photo author: ACM) and b. area of transition between grassland and riverine forest (Photo author: AJCA). Vegetation cover: MapBiomas (www.mapbiomas.org). Reserve delimitation: IBGE.

Figure 2

Interaction network of three stingless bee species and the 30 most frequent species in honey and pollen samples (Table S3). Bars connecting bee species and plant species indicate reported interaction (i.e. that plant species was present in the sequencing reads of pollen and/or honey metabarcoding in significant numbers). Some plant species are represented by numbers: 1. Croton conduplicatus; 2. Eucalyptus; 3. Myrtaceae; 4. Clusia criuva; 5. Myrcia guianensis; 6. Miconia hirtella; 7. Myrcia splendens; 8. Byrsonima basiloba; 9. Byrsonima laxiflora; 10. Leandra polystachya; 11. Myrsine umbellata; 12. Acalypha; 13. Couepia; 14. Mabea fistulifera; 15. Fabaceae; 16. Myrcia tomentosa; 17. Ilex affinis; 18. Eugenia involucrata; 19. Moraceae; 20. Cecropia pachystachya; 21. Byrsonima crassifolia; 22. Schefflera macrocarpa; 23. Artocarpus heterophyllus; 24. Campomanesia pubescens; 25. Myrcia pubescens; 26. Stillingia; 27. Syzygium; 28. Pinus; 29. Banisteriopsis; 30. Borago officinalis; 31. Byrsonima viminifolia; 32. Melastomataceae; 33. Euphorbia potentilloides; 34. Asteraceae; 35. Rosa chinensis; 36. Copaifera; 37. Trema micranthum; 38. Terminalia.

Figure 3

Boxplot of Shannon diversity indexes of plant species found in the honey (dark grey) and pollen (light grey) pots. Boxplots display the median (thick horizontal middle bars), lower (0.25) and upper (0.75) quartile (box limiting thin horizontal bars), minimum and maximum values (vertical lines). Solid dots represent an individual outlier sample. On the left, the three studied bee species in lateral view and in scale to show body size: (a) Melipona rufiventris, (b) Scaptotrigona postica, (c) Tetragonisca angustula.

Figure 4

Non-metric multidimensional scaling (NMDS) plots showing plant composition of pot-pollen (a) and pot-honey (b) in samples from nests of the three studied bee species: Melipona rufiventris, Scaptotrigona postica, Tetragonisca angustula.

Figure 5

Relative read abundance of the 30 most frequent species found in honey (left half) and pollen (right half) samples of nests of three stingless bee species. From top to bottom: Melipona rufiventris, Scaptotrigona postica, Tetragonisca angustula. Plant species names are displayed alphabetically. Color in graph bars refers to the habitat of occurrence in Cerrado biome (savanna or forest). Non-identified species were not assigned to any habitat, thus are represented by grey bars.