Department of Environmental Sciences, Emory University, Atlanta, GA, USA.
Program in Population Biology, Ecology, and Evolution, Emory University, Atlanta, GA, USA.
Oecologia. 2021 Nov;197(3):577-588. doi: 10.1007/s00442-021-05036-0. Epub 2021 Sep 21.
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，即谁与谁在不同的群落中相互作用，是高度动态的，我们对相互作用的身份如何响应自然界中的干扰而变化知之甚少。生态位和饮食理论的一个预测是，资源生态位将扩大以弥补由干扰驱动的资源减少，但这在植物-传粉者系统中尚未通过对实地真实世界干扰的实证检验得到证实。在这里，我们使用对蔓紫菀（Ipomopsis aggregata）的长期花朵访问数据集进行测试，蔓紫菀是一种高山多年生草本植物，以检验其花朵访问生态位（即花访客丰富度）是否会响应自然发生的干旱干扰而发生变化。干旱年份的花卉资源较少，这可能会促使传粉者扩大觅食生态位，从而扩大植物的花朵访问生态位。我们将两年的干旱年份与三年的非干旱年份进行了比较，以分析蔓紫菀花朵访客的生态位宽度和群落组成的变化，预测干旱年份与非干旱年份相比，生态位宽度变宽，访客群落组成也会不同。与非干旱条件相比，我们发现干旱年份的生态位宽度具有统计学意义上的显著增加，但花朵访客群落组成没有统计学上的显著变化。我们的研究结果表明，植物的花朵访问生态位可能会对干扰表现出相当大的可塑性。如果增加的生态位重叠会影响传粉服务，这可能会对群落水平的稳定性以及功能后果产生广泛的影响。
