Data from: Bottom-up effects of host-plant species diversity and top-down effects of ants interactively increase plant performance

While plant diversity is well known to increase primary productivity, whether these bottom-up effects are enhanced by reciprocal top-down effects from the third trophic level is unknown. We studied whether pine tree species diversity, aphid-tending ants and their interaction determined plant performance and arthropod community structure. Plant diversity had a positive effect on aphids, but only in the presence of mutualistic ants, leading to threefold greater number of both groups in the tri-specific cultures than in monocultures. Plant diversity increased ant abundance not only by increasing aphid number, but also by increasing ant recruitment per aphid. The positive effect of diversity on ants in turn cascaded down to increase plant performance; diversity increased plant growth (but not biomass), and this effect was stronger in the presence of ants. Consequently, bottom-up effects of diversity within the same genus and guild of plants and top-down effects from the third trophic level (predatory ants) interactively increased plant performance.众所周知，植物多样性可提升初级生产力（primary productivity），但此类自下而上调控效应（bottom-up effects）是否会受到第三营养级（trophic level）的反向自上而下调控作用（top-down effects）的增强，目前仍未明确。本研究探究了松树物种多样性、护蚜蚂蚁及其交互作用对植物表现与节肢动物（arthropod）群落结构的调控作用。研究发现，植物多样性对蚜虫种群具有正向调控效应，但仅在互利共生蚂蚁（mutualistic ants）存在的条件下才会显现；在此情形下，三树种混栽样地内的蚜虫与蚂蚁种群数量均达到单栽样地的三倍。植物多样性不仅通过提升蚜虫种群数量，还通过提高单头蚜虫所吸引的蚂蚁招募量（ant recruitment），来增加蚂蚁种群丰度。多样性对蚂蚁的正向效应继而通过营养级联作用，提升了植物表现：多样性可促进植物生长（但未对生物量产生显著影响），且该效应在蚂蚁存在时更为显著。综上，同属同功能群（guild）植物的多样性自下而上调控效应，与第三营养级的捕食性蚂蚁自上而下调控效应，可通过交互作用共同提升植物表现。