Data from: Ant diversity in Neotropical savannas: hierarchical processes acting at multiple spatial scales

1. Understanding what creates and maintains macroscale biodiversity gradients is a central focus of ecological and evolutionary research. Spatial patterns in diversity are driven by a hierarchy of factors operating at multiple scales. Historical and climatic factors drive large-scale patterns of diversity by affecting the size of regional species pools, while habitat heterogeneity or microhabitat characteristics further influence species coexistence at small scales. 2. We tested the degree to which the species-energy, historical factors, habitat heterogeneity and local environment hypotheses explain observed patterns of ant diversity across hierarchical spatial scales. 3. We sampled ground-dwelling ants at 29 sites within a Neotropical savanna region, the Brazilian Cerrado. We measured species density – an abundance-dependent diversity metric – and rarefied species richness – an abundance-independent metric – at spatial scales with varying grain sizes. For each hypothesis, two correlates were used to predict ant diversity patterns: i) species-energy: rainfall and productivity; ii) historical factors: historical variation in rainfall and refugial areas; iii) habitat heterogeneity: heterogeneity in greenness and diversity of land cover; iv) local factors: contents of sand and coarse fragments in the soil. 4. Ant diversity patterns correlated to net primary productivity and to the proportion of coarse fragments in the soil, corroborating the species-energy and local environment hypotheses, respectively. Soil negatively influenced species density, but not rarefied species richness, which was positively influenced by productivity. We found scale dependencies in the effects of soil/productivity on species density; productivity best predicted species density patterns at large scales, since sampling completeness offset the abundance-driven effects of soil. 5. Considering abundance differences may help to discern the mechanisms underlying the relationship between macroscale diversity patterns and its ecological drivers. Plant productivity affected ant diversity independently of abundance, possibly by limiting the size of regional species pools. On the other hand, soil properties had an abundance-dependent effect on ant diversity, indicating a sampling mechanism. Our findings are consistent with predictions of the hierarchical theory of diversity. Large-scale patterns of productivity limit regional diversity, an effect that cascades down to finer spatial scales, where soil properties influence the number of coexisting species.1. 阐明驱动与维持宏观尺度生物多样性梯度的机制，是生态学与进化生物学研究的核心议题。生物多样性的空间格局由多尺度下的层级式因子共同塑造：历史与气候因子通过调控区域物种库规模，驱动大尺度生物多样性格局；而生境异质性或微生境特征，则进一步在小尺度上影响物种共存过程。2. 本研究针对物种-能量假说、历史因子假说、生境异质性假说与局域环境假说，检验了四类假说在层级空间尺度下对蚁类多样性观测格局的解释效力。3. 我们在新热带稀树草原（Neotropical savanna）——巴西塞拉多（Brazilian Cerrado）区域内的29个样点，对地表栖息蚁类开展了采样。我们在不同粒度的空间尺度下，测定了两类多样性指标：物种密度（species density，一种依赖个体丰度的多样性度量）与稀疏化物种丰富度（rarefied species richness，一种不依赖个体丰度的多样性度量）。针对前述四类假说，各选取两项关联因子以预测蚁类多样性格局：i）物种-能量假说：降雨量与生产力水平；ii）历史因子假说：历史降雨量变异与生物避难所区域；iii）生境异质性假说：植被绿度异质性与土地覆盖多样性；iv）局域环境假说：土壤砂粒含量与粗碎屑占比。4. 蚁类多样性格局分别与净初级生产力（net primary productivity）及土壤粗碎屑占比呈显著相关，依次验证了物种-能量假说与局域环境假说。土壤属性对物种密度存在负向影响，但未显著影响稀疏化物种丰富度；而生产力水平则对稀疏化物种丰富度存在正向影响。我们发现土壤与生产力对物种密度的效应存在尺度依赖性：在大尺度下，生产力可最优预测物种密度格局，这是由于采样完备性抵消了土壤丰度驱动的效应。5. 考虑个体丰度差异，有助于解析宏观尺度生物多样性格局与其生态驱动因子间关联的内在机制。植物生产力可独立于丰度影响蚁类多样性，这可能通过限制区域物种库规模实现。与之相对，土壤属性对蚁类多样性的效应依赖于个体丰度，提示存在采样机制。本研究结果与多样性层级理论的预测相符：大尺度下的生产力限制区域多样性，该效应可向下传递至更精细的空间尺度，此时土壤属性将调控共存物种的数量。