Data from: Individual and interactive effects of chronic anthropogenic disturbance and rainfall on taxonomic, functional and phylogenetic composition and diversity of extrafloral nectary-bearing plants in Brazilian Caatinga

Chronic anthropogenic disturbance (CAD) and climate change represent two of the major threats to biodiversity globally, but their combined effects are not well understood. Here we investigate the individual and interactive effects of increasing CAD and decreasing rainfall on the composition and taxonomic (TD), functional (FD) and phylogenetic diversity (PD) of plants possessing extrafloral nectaries (EFNs) in semi-arid Brazilian Caatinga. EFNs attract ants that protect plants against insect herbivore attack and are extremely prevalent in the Caatinga flora. EFN-bearing plants were censused along gradients of disturbance and rainfall in Catimbau National Park in north-eastern Brazil. We recorded a total of 2,243 individuals belonging to 21 species. Taxonomic and functional composition varied along the rainfall gradient, but not along the disturbance gradient. There was a significant interaction between increasing disturbance and decreasing rainfall, with CAD leading to decreased TD, FD and PD in the most arid areas, and to increased TD, FD and PD in the wettest areas. We found a strong phylogenetic signal in the EFN traits we analysed, which explains the strong matching between patterns of FD and PD along the environmental gradients. The interactive effects of disturbance and rainfall revealed by our study indicate that the decreased rainfall forecast for Caatinga under climate change will increase the sensitivity of EFN-bearing plants to anthropogenic disturbance. This has important implications for the availability of a key food resource, which would likely have cascading effects on higher trophic levels.

长期人为干扰（Chronic Anthropogenic Disturbance, CAD）与气候变化是全球生物多样性面临的两大核心威胁，但二者的联合效应尚未得到充分解析。本研究以巴西东北部卡廷博国家公园（Catimbau National Park）内的半干旱卡廷加（Caatinga）植被为研究对象，探究了人为干扰强度增加与降水减少对携带花外蜜腺（Extrafloral Nectaries, EFNs）植物的群落组成、分类多样性（Taxonomic Diversity, TD）、功能多样性（Functional Diversity, FD）及系统发育多样性（Phylogenetic Diversity, PD）的单独及交互影响。花外蜜腺可吸引蚂蚁以保护植物免受植食性昆虫侵袭，在卡廷加植物区系中分布极为广泛。研究团队沿干扰梯度与降水梯度对具花外蜜腺的植物开展了全面普查，共记录到2243个个体，隶属于21个物种。分类与功能群落组成随降水梯度发生显著变化，但未随干扰梯度呈现明显差异。研究发现人为干扰与降水减少之间存在显著交互作用：在最干旱区域，人为干扰会导致分类、功能及系统发育多样性显著降低；而在最湿润区域，人为干扰则会提升上述三类多样性水平。本研究分析的花外蜜腺性状存在强烈的系统发育信号，这解释了环境梯度下功能多样性与系统发育多样性的变化模式高度匹配的现象。本研究揭示的干扰与降水的交互效应表明，气候变化背景下卡廷加地区预期的降水减少将会提升携带花外蜜腺植物对人为干扰的敏感性。该结果对关键食物资源的可获得性具有重要意义，并可能对更高营养级产生级联效应。