Instituto de Biologia, Universidade Federal de Uberlândia, Uberlândia, Brazil.
J Anim Ecol. 2020 Feb;89(2):412-422. doi: 10.1111/1365-2656.13111. Epub 2019 Oct 19.
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. 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. 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: (a) species-energy: rainfall and productivity; (b) historical factors: historical variation in rainfall and refugial areas; (c) habitat heterogeneity: heterogeneity in greenness and diversity of land cover; and (d) local factors: contents of sand and coarse fragments in the soil. 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. 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.
理解是什么创造和维持宏观生物多样性梯度是生态和进化研究的一个核心焦点。多样性的空间格局是由在多个尺度上运作的一系列因素驱动的。历史和气候因素通过影响区域物种库的大小来驱动大尺度多样性模式，而栖息地异质性或微生境特征则进一步影响小尺度上的物种共存。我们测试了物种-能量、历史因素、栖息地异质性和局部环境假说在多大程度上解释了在分层空间尺度上观察到的蚂蚁多样性模式。我们在巴西塞拉多的一个新热带草原地区的 29 个地点采集了地面蚂蚁。我们在具有不同粒度的空间尺度上测量了物种密度——一种依赖于丰度的多样性度量——和稀少物种丰富度——一种独立于丰度的度量。对于每个假说，我们使用两个相关因素来预测蚂蚁多样性模式：（a）物种-能量：降雨量和生产力；（b）历史因素：降雨量和避难所区域的历史变化；（c）栖息地异质性：绿色度和土地覆盖多样性的异质性；（d）局部因素：土壤中的沙子和粗碎片含量。蚂蚁多样性模式与净初级生产力和土壤中的粗碎片比例相关，分别证实了物种-能量和局部环境假说。土壤对物种密度有负面影响，但对稀少物种丰富度没有影响，而生产力对稀少物种丰富度有积极影响。我们发现土壤/生产力对物种密度的影响存在尺度依赖性；在大尺度上，生产力最好地预测了物种密度模式，因为采样的完整性抵消了土壤的丰度驱动效应。考虑丰度差异可能有助于辨别宏观多样性模式与其生态驱动因素之间关系的机制。植物生产力独立于丰度影响蚂蚁多样性，可能通过限制区域物种库的大小。另一方面，土壤特性对蚂蚁多样性具有丰度依赖性影响，表明存在一种采样机制。我们的发现与多样性的层次理论的预测一致。大尺度的生产力限制了区域多样性，这种效应向下级空间尺度传递，在那里土壤特性影响共存物种的数量。
