Data from: Rising atmospheric CO2 is reducing the protein concentration of a floral pollen source essential for North American bees

At present, there is substantive evidence that the nutritional content of agriculturally important food crops will decrease in response to rising levels of atmospheric carbon dioxide, Ca. However, whether Ca-induced declines in nutritional quality are also occurring for pollinator food sources is unknown. Flowering late in the season, goldenrod (Solidago spp.) pollen is a widely available autumnal food source commonly acknowledged by apiarists to be essential to native bee (e.g. Bombus spp.) and honeybee (Apis mellifera) health and winter survival. Using floral collections obtained from the Smithsonian Natural History Museum, we quantified Ca-induced temporal changes in pollen protein concentration of Canada goldenrod (Solidago canadensis), the most widespread Solidago taxon, from hundreds of samples collected throughout the USA and southern Canada over the period 1842–2014 (i.e. a Ca from approx. 280 to 398 ppm). In addition, we conducted a 2 year in situ trial of S. canadensis populations grown along a continuous Ca gradient from approximately 280 to 500 ppm. The historical data indicated a strong significant correlation between recent increases in Ca and reductions in pollen protein concentration (r2 = 0.81). Experimental data confirmed this decrease in pollen protein concentration, and indicated that it would be ongoing as Ca continues to rise in the near term, i.e. to 500 ppm (r2 = 0.88). While additional data are needed to quantify the subsequent effects of reduced protein concentration for Canada goldenrod on bee health and population stability, these results are the first to indicate that increasing Ca can reduce protein content of a floral pollen source widely used by North American bees.

目前已有充分确凿的证据表明，受大气二氧化碳（atmospheric carbon dioxide，文中简称Ca）浓度升高的影响，具有农业经济价值的粮食作物的营养成分含量会出现下降。然而，传粉昆虫的食物来源是否也会因Ca浓度升高而出现营养品质下降，这一问题尚未明确。作为秋季广泛可获取的食物来源，花期较晚的一枝黄花属（Solidago spp.）花粉被养蜂界普遍认为是本土野生蜂类（如熊蜂属Bombus spp.）与西方蜜蜂（Apis mellifera）维持健康及越冬存活的关键食物。本研究利用史密森尼自然历史博物馆（Smithsonian Natural History Museum）馆藏的植物标本，对1842年至2014年间采自美国全境及加拿大南部的数百份加拿大一枝黄花（Solidago canadensis，分布最广的一枝黄花属分类群）花粉样品进行了定量分析，揭示了Ca浓度升高导致的花粉蛋白质浓度的时间动态变化，该时段内Ca浓度约从280ppm升至398ppm。此外，本研究还开展了为期2年的原位试验，对生长在连续Ca浓度梯度（约280ppm至500ppm）环境下的加拿大一枝黄花种群进行了观测。历史标本数据显示，近期Ca浓度升高与花粉蛋白质浓度下降之间存在高度显著的相关性（决定系数r²=0.81）。原位试验数据验证了这一下降趋势，并表明随着Ca浓度在近期继续升高至500ppm，该下降趋势仍将持续（决定系数r²=0.88）。尽管仍需更多数据来量化加拿大一枝黄花花粉蛋白质浓度下降对蜂类健康及种群稳定性的后续影响，但本研究结果首次证实，Ca浓度升高会降低北美蜂类广泛利用的一种花粉食物来源的蛋白质含量。