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Climate warming in the coming decades may affect diapause in insect species which use it to survive unfavorable winter conditions. Plebeia droryana (Friese) (Hymenoptera: Apidae: Meliponini) is a highly eusocial bee species that exhibits reproductive diapause and inhabits southern South America where winter temperatures may fall below 10°C, or even below 0°C in extreme years. In this paper, we evaluate whether P. droryana might terminate diapause during winter under laboratory conditions. We initially kept colonies of P. droryana at 8°C in a biochemical oxygen demand chamber, and then raised the temperature by 2°C every 3 d until the cessation of diapause was detected, as indicated by the onset of brood cell building and subsequent egg-laying by queens. We found that the termination of diapause in P. droryana could be achieved at temperatures between 16°C and 22°C, resulting in typical postdiapause brood cell building and egg-laying rates. Our binomial generalized linear mixed model indicated that only temperature, but no time or temperature-time interaction, explained the probability of termination of diapause in P. droryana. Again, only temperature, but no time or temperature-time interaction, significantly affected amount of brood cell built postdiapause in this species. These data suggest that the levels of predicted climate warming in the geographic range of P. droryana over the coming decades will probably result in these populations abandoning diapause behavior. These results have important implications regarding the ecological service of crop and wild plant pollination provided by this species. [ABSTRACT FROM AUTHOR]

Climate changes are predicted to affect the diapause of many insect species around the world adversely. In this context, bees are of interest due to their pollination services. In southern Brazil, the highly eusocial bee species Plebeia droryana (Friese) (Hymenoptera: Apidae: Meliponini) exhibits reproductive diapause in response to the region's rigorous winters. That diapause is characterized by a temporary interruption in brood cell construction by nurse bees and egg-laying by the queen, regardless of other internal tasks underway in the nests. In this study, we evaluated whether P. droryana enter diapause under experimental conditions. P. droryana colonies were kept in a germination chamber, and the temperature was progressively reduced from 20°C over a period of a few weeks until diapause was detected. Additionally, we also estimated the environmental conditions in the actual geographic range occupied by P. droryana and modeled it for predicted changes in climate up to the year 2080. Our findings indicate that P. droryana enter diapause between 10 and 8°C. We also found that the current minimum winter temperature (10.1°C, median) in the distributional range of P. droryana will probably rise (13.4°C, median). Thus, if our experimental data are somewhat accurate, ~36% of the southern Brazilian P. droryana population may be active during the expected milder winter months in 2080. In this scenario, there may be a larger demand for pollen and nectar for that bee species. Greater conservation efforts will be required to preserve P. droryana populations and keep them viable in the coming decades. [ABSTRACT FROM AUTHOR]

Alternative pollinators can ensure pollination services if the availability of the managed or most common pollinator is compromised. In this study, the behavior and pollination efficiency of Apis mellifera L. and two species of stingless bees, Plebeia emerina Friese and Tetragoniscafiebrigi Schwarz, were evaluated and compared in flowers of Brassica napus L. 'Hyola 61'. A. mellifera was an efficient pollinator when collecting nectar because it effectively touched the reproductive organs of the flower. In contrast, stingless bees were efficient pollinators only when collecting pollen. The number of pollen grains deposited on the stigma after a single visit by worker bees of the three species was greater than the number of grains resulting from pollination without the bee visits. On average, the three species deposited enough pollen grains to fertilize all of the flower ovules. A. mellifera and P emerina had similar pollination efficiency because no significant differences were observed in the characteristics of the siliques produced. Although T. fiebrigi is also an effective pollinator, the seed mass produced by their pollination was lower. Native bees promoted similar rates of fruit set compared with A. mellifera. Thus, P. emerina has potential to be used for pollination in canola crops. [ABSTRACT FROM AUTHOR]