Cahill James F, Elle Elizabeth, Smith Glen R, Shore Bryon H
Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada.
Ecology. 2008 Jul;89(7):1791-801. doi: 10.1890/07-0719.1.
Plants engage in diverse and intimate interactions with unrelated taxa. For example, aboveground floral visitors provide pollination services, while belowground arbuscular mycorrhizal fungi (AMF) enhance nutrient capture. Traditionally in ecology, these processes were studied in isolation, reinforcing the prevailing assumption that these above- and belowground processes were also functionally distinct. More recently, there has been a growing realization that the soil surface is not a barrier to many ecological interactions, particularly those involving plants (who live simultaneously above and below ground). Because of the potentially large impact that mycorrhizae and floral visitors can have on plant performance and community dynamics, we designed an experiment to test whether these multi-species mutualisms were interdependent under field conditions. Using benomyl, a widely used fungicide, we suppressed AMF in a native grassland, measuring plant, fungal, and floral-visitor responses after three years of fungal suppression. AMF suppression caused a shift in the community of floral visitors from large-bodied bees to small-bodied bees and flies, and reduced the total number of floral visits per flowering stem 67% across the 23 flowering species found in the plots. Fungal suppression has species-specific effects on floral visits for the six most common flowering plants in this experiment. Exploratory analyses suggest these results were due to changes in floral-visitor behavior due to altered patch-level floral display, rather than through direct effects of AMF suppression on floral morphology. Our findings indicate that AMF are an important, and overlooked, driver of floral-visitor community structure with the potential to affect pollination services. These results support the growing body of research indicating that interactions among ecological interactions can be of meaningful effect size under natural field conditions and may influence individual performance, population dynamics, and community structure.
植物与不相关的分类群进行着多样而密切的相互作用。例如，地上的访花者提供传粉服务，而地下的丛枝菌根真菌（AMF）则增强养分获取。在传统生态学中，这些过程是孤立研究的，强化了一种普遍的假设，即这些地上和地下过程在功能上也是不同的。最近，人们越来越意识到土壤表面并非许多生态相互作用的障碍，尤其是那些涉及植物（它们同时生活在地上和地下）的相互作用。由于菌根和访花者可能对植物表现和群落动态产生巨大影响，我们设计了一项实验来测试这些多物种共生关系在田间条件下是否相互依赖。我们使用了一种广泛使用的杀菌剂苯菌灵，在一片原生草原上抑制AMF，在真菌抑制三年后测量植物、真菌和访花者的反应。AMF抑制导致访花者群落从大体型蜜蜂转变为小体型蜜蜂和苍蝇，并使样地中发现的23种开花植物每个花茎的访花总数减少了67%。在本实验中，真菌抑制对六种最常见开花植物的访花有物种特异性影响。探索性分析表明，这些结果是由于斑块水平的花展示改变导致访花者行为变化，而不是由于AMF抑制对花形态的直接影响。我们的研究结果表明，AMF是访花者群落结构的一个重要且被忽视的驱动因素，有可能影响传粉服务。这些结果支持了越来越多的研究，表明生态相互作用之间的相互作用在自然田间条件下可能具有有意义的效应大小，并可能影响个体表现、种群动态和群落结构。
