Drivers of brood parasitism in solitary bees across a South American dryland ecoregion

Abstract

Wild bees are parasitized by a variety of organisms, including those that attack brood cells within nests. Brood parasitism reduces reproductive output by increasing offspring mortality, with potential impacts on the persistence of bee populations. Understanding the biotic and abiotic drivers of parasitism in solitary bees becomes crucial under current anthropogenic environmental changes. We evaluated how nest and brood cell abundance, climate, and latitude drive brood parasitism in cavity-nesting solitary bee communities across a broad environmental gradient in the Monte Desert of Argentina. Parasitism rates at the community level increased with decreasing total nest and brood cell abundance and temperature. Across the gradient, parasitism decreased with increasing latitude. The overall parasitism rate was mainly determined by the prevalence of parasitized nests rather than by parasitism intensity within those nests, suggesting that parasitism pressure depends more on the likelihood of hosts being parasitized than on the extent of infestation within each parasitized nest.