Medina Nagore G, Bowker Matthew A, Hortal Joaquín, Mazimpaka Vicente, Lara Francisco
Departamento de Biología (Botánica), Facultad de Ciencias, Universidad Autónoma de Madrid, Campus de Cantoblanco, C/Darwin 2, 28049, Madrid, Spain.
Department of Botany, Faculty of Sciences, South Bohemia University, Na Zlate Stoce 1, 37005, Ceske Budejovice, Czech Republic.
Oecologia. 2018 Mar;186(3):805-816. doi: 10.1007/s00442-018-4066-x. Epub 2018 Jan 18.
Species richness is influenced by a nested set of environmental factors, but how do these factors interact across several scales? Our main aim is to disentangle the relative importance of environmental filters and the species pool on the richness of epiphytic bryophytes across spatial scales. To do so, we sampled epiphytic bryophytes in 43 oak forests across the northwest of the Iberian Peninsula. As predictors we used climate, descriptors of forest structure and micro-environment. We applied structural equation modeling to relate these variables with richness and cover at three scales: locality (forest), stand (three stands per forest), and sample (a quadrate in a tree). We assumed top-down relationships, so that large-scale variables influenced lower scale variables, and in which cover directly influenced richness. Richness at the next larger scale (locality to stand and stand to sample) is considered a surrogate of the species pool and included as a predictor of richness at the next smaller scale. Environmental variables explain locality richness, but as we decrease the spatial scale, its importance decreases and the dependence on species pool increases. In addition, we found unexpected bottom-up relationships (between micro-scale environment to locality richness). Our results point to the scale dependence of niche vs. neutral processes: niche processes are important at the locality (forest) scale, while neutral processes are significant at the small (sample) scale. We propose a modified conceptualization of the factors influencing biodiversity at different spatial scales by adding links across different scales (between micro-environment and locality-scale richness in our study).
物种丰富度受到一系列嵌套环境因素的影响，但这些因素如何在多个尺度上相互作用呢？我们的主要目标是厘清环境过滤和物种库对伊比利亚半岛西北部不同空间尺度上附生苔藓植物丰富度的相对重要性。为此，我们在伊比利亚半岛西北部的43片橡树林中对附生苔藓植物进行了采样。作为预测因子，我们使用了气候、森林结构和微环境的描述指标。我们应用结构方程模型将这些变量与三个尺度上的丰富度和盖度联系起来：地点（森林）、林分（每片森林三个林分）和样本（树上的一个样方）。我们假设存在自上而下的关系，即大尺度变量影响小尺度变量，且盖度直接影响丰富度。下一个更大尺度（从地点到林分以及从林分到样本）的丰富度被视为物种库的替代指标，并作为下一个更小尺度丰富度的预测因子。环境变量可以解释地点丰富度，但随着我们减小空间尺度，其重要性降低，而对物种库的依赖性增加。此外，我们还发现了意外的自下而上的关系（从微观尺度环境到地点丰富度）。我们的结果表明生态位与中性过程的尺度依赖性：生态位过程在地点（森林）尺度上很重要，而中性过程在小（样本）尺度上很显著。我们通过添加不同尺度之间的联系（在我们的研究中是微观环境与地点尺度丰富度之间的联系），提出了一个影响不同空间尺度生物多样性的因素的改进概念。
