Data from: Parental frequencies and spatial configuration shape bumblebee behavior and floral isolation in hybridizing Rhinanthus

To shed light on the role played by pollinators in the diversification of angiosperms, focus is needed on how floral isolation varies locally in the early stages of plant divergence. The few studies performed so far have often used species pairs with distinct pollination syndromes and contrasting floral displays. Here, we focus on a hybridizing pair (Rhinanthus minor and R. angustifolius) with strong similarities in flower morphology and pollinators (bumblebees). We examined how ethological isolation changes locally in relation to relative Rhinanthus frequencies, spatial configurations, and pollinator assemblages. Interestingly, floral divergence based on adaptation to different pollinators is unlikely in Rhinanthus: no relationship was found between floral isolation and the local pollinator assemblage. In contrast, species frequency and spatial arrangement strongly influenced bumblebee behavior, ethological isolation, and thus potentially hybrid formation. When both Rhinanthus were present in equal proportions, bees generally preferred the more rewarding and conspicuous species. However, when the Rhinanthus frequencies were unbalanced, the more abundant species was preferred, although this was less pronounced when the less rewarding R. minor predominated. Ethological isolation is highly sensitive to site characteristics, and can be as high as in species with contrasting floral displays and pollinator suites, even though flowers are similar.

为阐明传粉者（pollinators）在被子植物（angiosperms）的物种多样化进程中所扮演的角色，相关研究需聚焦于植物分化早期阶段花隔离（floral isolation）如何在局域尺度上发生变化。迄今为止开展的少数相关研究，多选用具有迥异传粉综合征（pollination syndromes）与差异化花部展示（floral displays）的物种对展开实验。本研究聚焦于一对正在发生杂交的物种：小鼻花（Rhinanthus minor）与狭叶鼻花（R. angustifolius），二者的花部形态与传粉者（均为熊蜂（bumblebees））均高度相似。我们探讨了行为隔离（ethological isolation）在局域尺度下的变化规律，及其与鼻花属植物相对频率、空间配置以及传粉者类群（pollinator assemblages）之间的关联。值得注意的是，鼻花属植物不太可能因适应不同传粉者而产生花部分化：研究未发现花隔离与局域传粉者类群之间存在任何关联。与之相反，物种相对频率与空间排布强烈影响了熊蜂的行为、行为隔离水平，进而可能对杂交物种的形成产生作用。当两种鼻花属植物以等比例共存时，熊蜂通常会优先选择奖励更为丰厚、花展示更为醒目的物种。然而，当二者的相对比例失衡时，熊蜂会更偏好数量占优的物种；但当奖励较低的小鼻花占据种群优势时，这种偏好性会相对减弱。尽管两种鼻花的花部形态高度相似，但其行为隔离对生境特征极为敏感，其强度甚至可与那些花部特征与传粉类群均存在显著差异的物种对相当。