The composition of plant–pollinator interactions—i.e., who interacts with whom in diverse communities—is highly dynamic, and we have a very limited understanding of how interaction identities change in response to perturbations in nature. One prediction from niche and diet theory is that resource niches will broaden to compensate for resource reductions driven by perturbations, yet this has not been empirically tested in plant–pollinator systems in response to real-world perturbations in the field. Here, we use a long-term dataset of floral visitation to Ipomopsis aggregata, a montane perennial herb, to test whether the breadth of its floral visitation niche (i.e., flower visitor richness) changed in response to naturally occurring drought perturbations. Fewer floral resources are available in drought years, which could drive pollinators to expand their foraging niches, thereby expanding plants’ floral visitation niches. We compared two drought years to three non-drought years to analyze changes in niche breadth and community composition of floral visitors to I. aggregata, predicting broadened niche breadth and distinct visitor community composition in drought years compared to non-drought years. We found statistically significant increases in niche breadth in drought years as compared to non-drought conditions, but no statistically distinguishable changes in community composition of flower visitors. Our findings suggest that plants’ floral visitation niches may exhibit considerable plasticity in response to disturbance. This may have widespread consequences for community-level stability as well as functional consequences if increased niche overlap affects pollination services.

植物-传粉者相互作用的组成——即在不同社区中谁与谁相互作用——是高度动态的，我们对相互作用身份如何随着自然界的扰动而变化的了解非常有限。生态位和饮食理论的一个预测是，资源生态位将扩大以补偿由扰动驱动的资源减少，但这尚未在植物 - 传粉系统中针对该领域的真实世界扰动进行经验测试。在这里，我们使用了对Ipomopsis agregata的花卉访问的长期数据集，一种山地多年生草本植物，以测试其花卉访问生态位的广度（即花卉访客丰富度）是否因自然发生的干旱扰动而发生变化。干旱年份可用的花卉资源较少，这可能会促使传粉媒介扩大其觅食生态位，从而扩大植物的花卉访问生态位。我们比较了两个干旱年和三个非干旱年，以分析I. agregata 花卉访客的生态位宽度和群落组成的变化，预测与非干旱年份相比，干旱年份的生态位宽度和不同的游客群落组成有所扩大。我们发现与非干旱条件相比，干旱年份的生态位宽度在统计学上显着增加，但花卉访客的群落组成没有统计学上可区分的变化。我们的研究结果表明，植物的花卉访问生态位可能会在响应干扰时表现出相当大的可塑性。如果生态位重叠增加影响授粉服务，这可能对社区水平的稳定性以及功能后果产生广泛的影响。