Seasonal and diurnal patterns of activity in honeybees (Apis spp.) on the northern edge of the Asian tropics; their implications for the climate-change resilience of pollination

Abstract

Apis honeybees are very important pollinators in tropical Asia but their diversity declines rapidly north of the tropics. This suggests that climate is a major control on their distributions and that climate change may influence the services they provide. Four Apis honeybees coexist in a flower-rich botanical garden in Yunnan, China, on the northern margin of the tropics (21o41′N): A. florea and A. andreniformis (small, open-nesting), A. cerana (medium, cavity-nesting), and A. dorsata (large, open-nesting). We made standardized observations of their diurnal and seasonal activity patterns and recorded temperature, humidity, and solar radiation at flowers being visited. A. dorsata comprised two-thirds of honeybee individuals observed, although this species was largely absent from July to November. A. cerana was active on each day that observations were made and tolerated temperatures of 7℃–41.5℃ (including observations from two other sites in Yunnan). The other species had higher minimum temperature thresholds for activity, but A. florea had a higher maximum temperature tolerance (46.5℃) and A. dorsata was sometimes active at night. Generalized linear models showed abundances of A. cerana and A. dorsata had positive relationships with numbers of flowers and negative ones with temperature. A. florea abundance had a positive relationship with temperature, while the presence of A. andreniformis was positively related to temperature and humidity. Apis bees visited 48.6% of the flower species observed. Impacts of projected warming over coming decades are expected to vary among species, but overall pollination services by honeybees at this site seem likely to be resilient.