Factors affecting the health and sustainability of stingless bees (Hymenoptera, Meliponini) colonies in Ecuador: interactions between management practices, pesticide exposure, floral resources, and pathogens

Ecuador, located in the Neotropical region of South America, is a notable example of a megadiverse country, with approximately 200 species of stingless bees and more than 700 meliponicultors. The country is experiencing a significant growth in the practice of meliponiculture, concurrent with its status as a hotspot for native stingless bee diversity. As with other Hymenoptera, bees of the tribe Meliponini are experiencing a decline in population numbers, with this decline occurring due to a number of factors that either alone or in interaction reduce the number of their populations annually. The present study aims to provide empirical evidence on factors of anthropogenic origin, such as pesticides, human management, as well as those of natural origin, including pollen resources, pests, and pathogens, that influence the health status of stingless bees in Ecuador. In addition to the provision of guidance on actions to be taken, ensuring their positive impact on the conservation and reduction of stingless bee colony deaths.
By November 2024 (systematic review), a total of 15 pathogens and pests that affect the health of stingless bee colonies had been reported, as well as 26 contaminants that have lethal or sublethal effects on the lives of stingless bees (Study 1). The health of stingless bees in Ecuador is influenced by various factors, including the presence of pesticides and other contaminants in the environment, which can access the interior of the nest. Additionally, pests, some of which can become pathogenic, also pose a threat. In cerumen, a product of stingless bees, both for internal use in the nest and for application to humans, glyphosate and AMPA (a metabolite) were detected, along with heavy metals and metalloids (As, Cd, Cr, Ni, Pb) (Study 4). The estimated annual mortality rate of 15% for stingless bees farmed for honey production and sale (Melipona, Tetragonisca, Scaptotrigona, the latter genus depending on the country's climatic region) enabled the identification of areas for improvement through the application of good management practices (Study 5).
The type and diversity of pollen collected by bees affects their nutrition, which in turn impacts their immune system, their ability to resist pathogens, and their capacity to recover from stress caused by pesticides. Using two techniques — electron microscopy-morphometry (Study 2) and DNA barcoding (Study 3)— 27 plant families and 18 genera were identified, and up to 34 species, respectively. The first technique was based on pollen grain counts to determine the abundance of families and genera, with Melastomataceae (Miconia) and Asteraceae (Bidens) identified as the main sources of pollen. The most abundant species and genera present per sample for the second technique were Prockia crucis, Coffea canephora, Miconia nervosa, Laurus nobilis, Theobroma sp., Miconia notabilis, Artocarpus sp., Croton sp., Euphorbia sp., Cecropia ficifolia, Mikania sp., and Ophryosporus sp., in order of number of readings per ASV (Amplicon Sequence Variant).
The results of this integrated study provide a basis for the adoption of sustainable practices by meliponiculture farmers and policymakers, thereby supporting the survival of native stingless bees and preventing the overexploitation of these important pollinators in Ecuador's tropical regions.