Data from: Seed-dispersal networks respond differently to resource effects in open and forest habitats

While patterns in species diversity have been well studied across large-scale environmental gradients, little is known about how species' interaction networks change in response to abiotic and biotic factors across such gradients. Here we studied seed-dispersal networks on 50 study plots distributed over ten different habitat types on the southern slopes of Mt. Kilimanjaro, Tanzania, to disentangle the effects of climate, habitat structure, fruit diversity and fruit availability on different measures of interaction diversity. We used direct observations to record the interactions of frugivorous birds and mammals with fleshy-fruited plants and recorded climatic conditions, habitat structure, fruit diversity and availability. We found that Shannon interaction diversity (H) increased with fruit diversity and availability, whereas interaction evenness (EH) and network specialization (H2') responded differently to changes in fruit availability depending on habitat structure. The direction of the effects of fruit availability on EH and H2' differed between open habitats at the mountain base and structurally complex habitats in the forest belt. Our findings illustrate that interaction networks react differently to changes in environmental conditions in different ecosystems. Hence, our findings demonstrate that future projections of network structure and associated ecosystem functions need to account for habitat differences among ecosystems.

尽管物种多样性的分布格局在大尺度环境梯度下已得到充分研究，但目前对物种互作网络如何响应此类梯度下的非生物与生物因子变化仍知之甚少。本研究以坦桑尼亚乞力马扎罗山南坡10种不同生境类型下的50个样地为研究对象，旨在厘清气候、生境结构、果实多样性与果实可获得性对不同互作多样性指标的影响。我们通过直接观测记录了食果鸟类与哺乳动物对肉质果植物的取食互作，并同步记录了气候条件、生境结构、果实多样性与可获得性数据。研究结果显示，香农互作多样性（Shannon interaction diversity, H）随果实多样性与可获得性的提升而升高；而交互均匀度（interaction evenness, EH）与网络特化程度（network specialization, H2'）对果实可获得性变化的响应则因生境结构而异。果实可获得性对EH与H2'的影响方向，在山地基部的开阔生境与林带内结构复杂的生境之间存在显著差异。本研究结果表明，不同生态系统中的物种互作网络对环境条件变化的响应模式存在差异。因此，未来针对网络结构与相关生态系统功能的预测研究，需要纳入生态系统间的生境差异这一考量因素。