Plant protection services mediated by extrafloral nectaries decline with aridity but are not influenced by chronic anthropogenic disturbance in Brazilian Caatinga

1. Most terrestrial species occur in human-modified landscapes that are experiencing climate change. In addition to direct impacts on species, both anthropogenic disturbance and climate change can have important effects through changes in species interactions, including the disruption of ecological services provided by them. 2. Here we investigate how chronic anthropogenic disturbance (CAD) and aridity affect the effectiveness of plant protection services provided by ants to plants bearing extrafloral nectaries (EFNs). 3. The study was conducted across 13 01-ha plots distributed along CAD and aridity gradients in Caatinga vegetation of northeastern Brazil. We focused on Pityrocarpa moniliformis, the most abundant and widely distributed EFN-bearing tree species occurring in our study area, and used experimental attack rates on termites as a measure of effectiveness of ant protection services. We investigated the relative roles of nectar production (volume and concentration) and ant...1. 多数陆生生物栖息于正经历气候变化的人为改造景观中。除对生物产生直接影响外，人为干扰与气候变化均可通过改变物种间相互作用产生重要生态效应，其中包括破坏生物所提供的生态系统服务。 2. 本研究旨在探讨长期人为干扰（chronic anthropogenic disturbance, CAD）与干旱程度如何影响蚂蚁为携带花外蜜腺（extrafloral nectaries, EFNs）的植物提供的护植服务效能。 3. 本研究在巴西东北部的卡廷加（Caatinga）植被区内开展，共设置13块面积为1公顷的样地，样地沿长期人为干扰与干旱梯度分布。研究聚焦于研究区内分布最广、丰度最高的具花外蜜腺树种——单形皮特里木（Pityrocarpa moniliformis），并以白蚁的实验攻击率作为蚂蚁护植服务效能的衡量指标。本研究同时探讨了花蜜分泌量（体积与浓度）以及蚂蚁...