Rose-Person Annika, Santiago Louis S, Rafferty Nicole E
Department of Evolution, Ecology and Organismal Biology, University of California, Riverside, 900 University Avenue, Riverside, CA 92521, USA.
Department of Botany & Plant Sciences, University of California, Riverside, 900 University Avenue, Riverside, CA 92521, USA.
Ann Bot. 2025 Feb 8;135(1-2):153-164. doi: 10.1093/aob/mcae048.
Pollinators provide critical ecosystem services, maintaining biodiversity and benefitting global food production. However, plants, pollinators and their mutualistic interactions can be affected by drought, which has increased in severity and frequency under climate change. Using two annual, insect-pollinated wildflowers (Phacelia campanularia and Nemophila menziesii), we asked how drought impacts floral traits and foraging preferences of a solitary bee (Osmia lignaria) and explored potential implications for plant reproduction.
In greenhouses, we subjected plants experimentally to drought to induce water stress, as verified by leaf water potential. To assess the impact of drought on floral traits, we measured flower size, floral display size, nectar volume and nectar sugar concentration. To explore how drought-induced effects on floral traits affected bee foraging preferences, we performed choice trials. Individual female bees were placed into foraging arenas with two conspecific plants, one droughted and one non-droughted, and were allowed to forage freely.
We determined that P. campanularia is more drought tolerant than N. menziesii, based on measures of turgor loss point, and confirmed that droughted plants were more drought stressed than non-droughted plants. For droughted plants of both species, the floral display size was reduced and the flowers were smaller and produced less, more-concentrated nectar. We found that bees preferred non-droughted flowers of N. menziesii. However, bee preference for non-droughted P. campanularia flowers depended on the time of day and was detected only in the afternoon.
Our findings indicate that bees prefer to visit non-droughted flowers, probably reducing pollination success for drought-stressed plants. Lack of preference for non-droughted P. campanularia flowers in the morning might reflect the higher drought tolerance of this species. This work highlights the potentially intersecting, short-term physiological and pollinator behavioural responses to drought and suggests that such responses might reshape plant-pollinator interactions, ultimately reducing reproductive output for less drought-tolerant wildflowers.
传粉者提供关键的生态系统服务，维持生物多样性并造福全球粮食生产。然而，植物、传粉者及其互利共生关系会受到干旱影响，而在气候变化下，干旱的严重程度和发生频率都有所增加。我们以两种一年生虫媒野花（钟花紫堇和门氏蓝钟花）为研究对象，探究干旱如何影响独居蜂（木蜂）的花部特征和觅食偏好，并探讨其对植物繁殖的潜在影响。
在温室中，我们通过实验使植物遭受干旱以诱导水分胁迫，叶片水势验证了这一胁迫。为评估干旱对花部特征的影响，我们测量了花的大小、花序大小、花蜜量和花蜜糖浓度。为探究干旱对花部特征的影响如何影响蜜蜂的觅食偏好，我们进行了选择试验。将雌蜂个体放入有两株同种植物的觅食区域，一株干旱处理，一株未干旱处理，让其自由觅食。
基于膨压丧失点的测量，我们确定钟花紫堇比门氏蓝钟花更耐旱，并证实干旱处理的植物比未干旱处理的植物水分胁迫更严重。对于两种植物的干旱处理植株，花序大小减小，花朵变小，花蜜产量减少但浓度增加。我们发现蜜蜂更喜欢门氏蓝钟花的未干旱花朵。然而，蜜蜂对钟花紫堇未干旱花朵的偏好取决于一天中的时间，且仅在下午被检测到。
我们的研究结果表明，蜜蜂更喜欢访问未干旱的花朵，这可能会降低受干旱胁迫植物的授粉成功率。早上对钟花紫堇未干旱花朵缺乏偏好可能反映了该物种较高的耐旱性。这项工作突出了对干旱的短期生理和传粉者行为反应可能存在的交叉，并表明这些反应可能重塑植物 - 传粉者相互作用，最终降低耐旱性较差的野花的繁殖产量。
