Across the globe, wild bees are threatened by ongoing natural habitat loss, risking the maintenance of plant biodiversity and agricultural production. Despite the ecological and economic importance of wild bees and the fact that several species are now managed for pollination services worldwide, little is known about how land use and beekeeping practices jointly influence gene flow. Using stingless bees as a model system, containing wild and managed species that are presumed to be particularly susceptible to habitat degradation, here we examine the main drivers of tropical bee gene flow. We employ a novel landscape genetic approach to analyse data from 135 populations of 17 stingless bee species distributed across diverse tropical biomes within the Americas. Our work has important methodological implications, as we illustrate how a maximum-likelihood approach can be applied in a meta-analysis framework to account for multiple factors, and weight estimates by sample size. In contrast to previously held beliefs, gene flow was not related to body size or deforestation, and isolation by geographic distance (IBD) was significantly affected by management, with managed species exhibiting a weaker IBD than wild ones. Our study thus reveals the critical importance of beekeeping practices in shaping the patterns of genetic differentiation across bee species. Additionally, our results show that many stingless bee species maintain high gene flow across heterogeneous landscapes. We suggest that future efforts to preserve wild tropical bees should focus on regulating beekeeping practices to maintain natural gene flow and enhancing pollinator-friendly habitats, prioritizing species showing a limited dispersal ability.

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Male flowers of the wind-pollinated, dioecious shrub Boehmeria caudata Sw. release pollen explosively, possibly stimulated by anther dehydration in response to temporarily dry conditions coupled with hydrostatic pressure in the filament. In the Brazilian Atlantic rain forest, the daily frequency of male flower anthesis peaked between 1000–1200 h (GMT −3) and was positively correlated with rising temperature, wind currents, and direct insolation, but negatively correlated with relative humidity. A generalized linear mixed model predicts the probability of pollen release under different conditions of relative humidity and wind. Receptive stigmas on female flowers were found at any time of day: individual stigmas were receptive (H2O2 test) for at least two days. Beetles and halictid bees were observed feeding on pollen from staminate flowers, but probably did not affect pollination because they did not seem to visit pistillate flowers. Individual plants of this apparently ruderal species grow along road edges and show aggregated (clumped) spatial dispersion. The overall sex ratio we found was 29 females to 43 males, with one monoecious plant in a total transect distance of 6319 m. Pollen traps were placed on the female plants to measure pollen arrival. Pollen capture was higher on the more exposed road-facing side and positively related to male plant density.