Management practices and seasonality affect stingless bee colony growth, foraging activity, and pollen diet in coffee agroecosystems

Abstract

Stingless bees are essential pollinators in tropical ecosystems. Yet compared to their temperate zone counterparts, we know very little about how they respond to agriculture-associated land use, or how this effect is modulated by seasonal variation. Coffee, a dominant crop across the tropics, is grown under diverse management practices, making coffee agroecosystems an important context in which to investigate effects of agricultural management on stingless bees. We evaluated the performance and pollen diet of replicated experimental colonies of the stingless bee Scaptotrigona mexicana in three habitats in a coffee-dominated landscape in southern Chiapas, Mexico: a conventional sun coffee farm, a shaded organic coffee farm, and a forest fragment. We asked how habitat and seasonality influenced colony weight, forager activity, and pollen diet over one year. We placed eight experimental colonies in three habitats (three each in coffee farms; two in forest) and monitored them monthly for colony weight and forager activity. We collected corbicular pollen loads from returning foragers and identified pollen morphospecies. We compared performance and diet metrics across habitats and between wet and dry seasons. Colony performance was dramatically worse in the sun coffee farm; all sun coffee colonies died during the study. Colony performance did not differ between shade coffee and forest. Pollen diet richness was lower in the sun coffee colonies, but all habitats shared the same core pollen morphospecies. Across habitats, colony weight and activity and pollen diet richness decreased during the wet season. Our study suggests that conventional sun coffee cannot support stingless bee colonies, likely because of combined effects of agrochemical exposure and floral resource scarcity. By contrast, shade coffee is equivalent to forests in supporting stingless bee colonies.