University of Michigan, Department of Ecology and Evolutionary Biology, United States
Background/Question/Methods
Stingless bees (Apidae: Meliponini) are important pollinators across the tropics. In Mesoamerica, increased cultivation of crops that rely on bee pollination has fueled interest in managing landscapes to promote wild stingless bee populations and reviving practices of stingless bee husbandry. At the same time, stingless bees face threats from habitat loss, exposure to agrichemicals, and direct exploitation by humans. Understanding how landscape context affects stingless bee foraging and colony health is therefore a pressing concern.
In this study, we compared colony growth, foraging activity, and pollen diet in replicated experimental colonies of the stingless bee Scaptotrigona mexicana in three habitats (forest fragment, organic shaded coffee farm, and conventional sun coffee farm) in a coffee-growing region of Chiapas, Mexico. We monitored experimental colonies monthly for one year, asking whether landscape context influenced colony health and activity, and whether floral resource availability (influenced by both habitat and seasonality) predicted pollen diet and colony performance.
Results/Conclusions
Colony performance differed substantially across habitats. Colonies in the conventional sun coffee farm showed reduced foraging activity and rapid weight loss during the initial months of the study; none of these colonies survived for the duration of the study. There was no difference in colony growth or foraging activity between the shaded coffee farm and forest fragment, but there was strong seasonality across habitats, with reduced foraging activity and growth during the wet season. This is consistent with evidence that floral resource availability is similar between these two habitats, and is much lower in the wet season than the dry season. Pollen diets were broadly overlapping across habitats, though PERMANOVA analysis indicated significant differences among habitats. Pollen diet diversity trended lower in sun coffee.
These results indicate that coffee farm management strongly influences stingless bee colony performance. The conventional sun coffee farm could not support stingless bee colonies, likely due to the negative effects of exposure to pesticides in this habitat, rather than reduced availability of floral resources. Our results highlight the importance of implementing agroecological management practices at the farm scale, and/or maintaining habitat heterogeneity at the landscape scale, to sustain stingless bee populations and consequent pollination services.
