Brazil has one of the world’s greatest diversities of stingless bee species. In the face of a challenging environmental scenario, it is important to understand the resources these tropical bees use as food sources. Aline Martins and collaborators investigated the floral preference of stingless bees in the Cerrado, sharing interesting results that can also be studied in other biomes. 

Bees and other animals visit flowers to collect food, and during this process, they facilitate plant reproduction, which generates new fruits and is essential to biodiversity. There are many species of pollinators, and they have preferences for specific types of flowers, depending on their colour, size, shape, and opening times. For example, hummingbirds visit some plants that match their tubular beaks, while bats pollinate flowers that are open during the night. 

Many species of stingless bees are generalists and visit a diversity of plant species to obtain enough nectar and pollen for their hives. The flowers these tropical bees will visit depend on the vegetation in their environment, but also the bee morphology. For instance, stingless bees have different sizes, which are correlated to the distance they can fly to obtain resources. 

It is still unclear how many plant species stingless bees visit and their preferences. A group of researchers led by Aline Martins investigated these questions recently (2023), studying three species of stingless bees: “uruçu-amarela” (Melipona rufiventris), “Mandaguari” (Scaptotrigona postica), and “jataí” (Tetragonisca angustula). Considering the practicality of studying these questions, this can be considered challenging research, as Brazil has a high diversity of plant species, and it is hard to track which flowers bees visited, especially in forest trees. But Martins and colleagues used an innovative technique that identified the plant species just by studying the pollen and nectar that bees had stored in their pots. This is possible due to the plant DNA, the small molecules inside cells that are unique to each species. These DNA molecules have sequences that can be read similarly to a barcode in a supermarket. 

In the research, hives from these three stingless bee species were inspected for six months, and the honey and pollen were analysed to identify the plant species collected across these months. The results show that Jataí, uruçu-amarela, and mandaguari are indeed generalist bees and they can visit around 50 plant species to get their carbohydrates, protein, and vitamins. 

In general, forest trees had a good representation in the food collected by these stingless bee foragers, an interesting result since foragers had various shrubs and herbaceous vegetation near their hives, but still, they would search farther away for some mass-flowering trees, at distances up to 600m. The plant species that were most visited were from these groups: 1. Myrtaceae, 2. Asteraceae, 3. Euphorbiaceae, 4. Melastomataceae, and 5. Malpighiaceae (see Figure 2 to identify common flowers from each group). The favourite kinds of plants had little white flowers with a lot of pollen available. 

Additionally, just by analysing the DNA in food stores from these stingless bees, it was possible to understand more of their foraging behaviour. Jataí bees, for example, collect pollen from various plant species, and because they are tiny bees, it is common for their workers to look for food alone, finding a variety of sources, while other species have recruitment strategies, directing the efforts towards a very good source, such as mass-flowering plants. 

Besides their ecological importance, stingless bees are culturally and economically significant, with sustainable beekeeping practices becoming more common in Brazil. Considering ongoing climate change, the Cerrado has been under intense deforestation, and understanding the needs of native species, such as stingless bees, is essential to protect its biodiversity. The research led by Martins answered important questions and opened doors to future studies investigating other biomes, as stingless bees are distributed across Brazil. 

References 

Martins, Aline C., et al. “Contrasting patterns of foraging behavior in neotropical stingless bees using pollen and honey metabarcoding.” Scientific Reports 13.1 (2023): 14474. 

Willmer, Pat. “Pollination and floral ecology.” Pollination and floral ecology. Princeton University Press, 2011.