A Phylogenetic Perspective on the Individual Species-Area Relationship in Temperate and Tropical Tree Communities

Ecologists have historically used species-area relationships (SARs) as a tool to understand the spatial distribution of species. Recent work has extended SARs to focus on individual-level distributions to generate individual species area relationships (ISARs). The ISAR approach quantifies whether individuals of a species tend have more or less species richness surrounding them than expected by chance. By identifying richness ‘accumulators’ and ‘repellers’, respectively, the ISAR approach has been used to infer the relative importance of abiotic and biotic interactions and neutrality. A clear limitation of the SAR and ISAR approaches is that all species are treated as evolutionarily independent and that a large amount of work has now shown that local tree neighborhoods exhibit non-random phylogenetic structure given the species richness. Here, we use nine tropical and temperate forest dynamics plots to ask: (i) do ISARs change predictably across latitude?; (ii) is the phylogenetic diversity in the neighborhood of species accumulators and repellers higher or lower than that expected given the observed species richness?; and (iii) do species accumulators, repellers distributed non-randomly on the community phylogenetic tree? The results indicate no clear trend in ISARs from the temperate zone to the tropics and that the phylogenetic diversity surrounding the individuals of species is generally only non-random on very local scales. Interestingly the distribution of species accumulators and repellers was non-random on the community phylogenies suggesting the presence of phylogenetic signal in the ISAR across latitude.

生态学家长期以来将物种-面积关系（species-area relationships, SARs）作为理解物种空间分布的经典工具。近期研究将SARs拓展至个体水平分布的分析，进而衍生出单物种-面积关系（individual species area relationships, ISARs）。ISAR方法可量化某一物种的个体周围的物种丰富度，是否显著高于或低于随机预期的水平。通过分别识别物种丰富度的“富集者”与“排斥者”，ISAR方法可用于推断非生物相互作用、生物相互作用以及中性过程的相对重要性。SAR与ISAR方法存在一个明显的局限：其将所有物种视为进化独立的单元，而当前已有大量研究表明，在给定物种丰富度的前提下，本地树木邻域会呈现出非随机的系统发育结构。本研究依托9个热带与温带森林动态样地，旨在探讨三个科学问题：（i）单物种-面积关系是否会随纬度呈现可预测的变化规律？（ii）物种富集者与排斥者邻域内的系统发育多样性，相较于基于观测物种丰富度的预期水平，是否存在显著升高或降低？（iii）物种富集者与排斥者在群落系统发育树上的分布是否呈现非随机模式？研究结果显示，从温带到热带，单物种-面积关系并未呈现出明确的变化趋势；且物种个体周围的系统发育多样性，通常仅在极小的局域尺度上呈现非随机特征。值得注意的是，物种富集者与排斥者的分布在群落系统发育树上呈现非随机模式，这表明单物种-面积关系在纬度梯度上存在系统发育信号。