Temperature and humidity changes that influence the way flowers grow can make bumblebees picky eaters 鈥� and climate change could make them even more so. This suggests that rising temperatures could have an impact on pollination rates, which are already in decline.
Charlotte Descamps and her colleagues at UCLouvain in Belgium . They found the bees were four times less likely to visit borage plants grown at 26掳C compared with those cultivated at 21掳C.
Borage is a bee-pollinated plant, with blue flowers evolved for attractiveness to bumblebees and honeybees. The team found that growing the plants at higher temperatures led to fewer open flowers per plant, a smaller overall floral area and lower nectar volume, all of which would make them attractive to pollinators.
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鈥淚f climate change raises the average temperature of the environment during spring or summer, this result demonstrates that the rise could impact on how wild species develop, which in turn could have impacts on what they can provide to pollinators,鈥� says at the University of Bristol, UK.
鈥淭he experimental bumblebees showed a distinct preference for the plants grown at 鈥榗urrent鈥� temperatures, which demonstrates that there may be a link between the physical changes in the plants and the choices made by the bees,鈥� he says.
In separate work, Rands and his colleagues have found that . The team offered bees the choice of artificial flowers generating higher or lower levels of humidity, while the reward for visiting the flowers (the amount of sugar solution) was the same.
In another experiment, Rands and his colleagues used artificial flowers where differing levels of humidity offered varying rewards. After some initial training to recognise these cues, the bees showed an improved ability to select which flowers to feed on.
鈥淚t鈥檚 not surprising that bumblebees are sensitive to humidity 鈥� it doesn鈥檛 just relate to a flower鈥檚 properties, but could be important in various parts of their life cycle, including when queens seek hibernation sites in autumn and seek nesting locations in spring, and to help the workers maintain healthy conditions within the nest to support the development of the bee larvae鈥�, says at the University of Greenwich, UK.
Floral humidity is a result of nectar evaporation and a plant鈥檚 internal water transport 鈥� which might be expected to increase in a warming world. Plants with more humid flowers may benefit, suggests Arnold, but with potential costs during periods of water stress, such as drought, which are likely to be more common in future.
鈥淭he studies both provide some really interesting insights into what affects whether a flower gets visited by bees or not, factors that clearly do influence how 鈥榞ood鈥� a flower is for the bee but which haven鈥檛 really been explored and tested methodically before,鈥� says Arnold. 鈥淭he take-home is that a bee鈥檚 decision to visit or avoid a flower is really nuanced.鈥�
搁别蹿别谤别苍肠别蝉:听滨苍蝉别肠迟蝉,听 (Descamps et al.), Journal of Experimental Biology, (Rands et al.)
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