Data from: Biogeographic, climatic and spatial drivers differentially affect α-, β- and γ-diversities on oceanic archipelagos

Island biogeographic studies traditionally treat single islands as units of analysis. This ignores the fact that most islands are spatially nested within archipelagos. Here, we took a fundamentally different approach and focused on entire archipelagos using species richness of vascular plants on 23 archipelagos worldwide and their 174 constituent islands. We assessed differential effects of biogeographic factors (area, isolation, age, elevation), current and past climate (temperature, precipitation, seasonality, climate change velocity) and intra-archipelagic spatial structure (archipelago area, number of islands, area range, connectivity, environmental volume, inter-island distance) on plant diversity. Species diversity of each archipelago (γ) was additively partitioned into α, β, nestedness and replacement β-components to investigate the relative importance of environmental and spatial drivers. Multiple regressions revealed strong effects of biogeography and climate on α and γ, whereas spatial factors, particularly number of islands, inter-island distance and area range, were key to explain β. Structural equation models additionally suggested that γ is predominantly determined by indirect abiotic effects via its components, particularly β. This highlights that β and the spatial arrangement of islands are essential to understand insular ecology and evolution. Our methodological framework can be applied more widely to other taxa and archipelago-like systems, allowing new insights into biodiversity origin and maintenance.

岛屿生物地理学研究传统上以单个岛屿作为分析单元，但这忽略了绝大多数岛屿在空间上隶属于群岛这一事实。本研究采用了截然不同的研究范式，聚焦于整个群岛尺度，以全球23个群岛及其所辖174个岛屿的维管植物物种丰富度为研究对象。我们评估了生物地理因子（岛屿面积、隔离度、形成年代、海拔）、当前与过去气候（温度、降水量、季节节律、气候变化速率）以及群岛内部空间结构（群岛总面积、岛屿数量、面积跨度、连通性、环境体量、岛间距离）对植物多样性的差异化影响。我们将每个群岛的物种多样性（γ多样性（gamma diversity））可加性分解为α多样性（alpha diversity）、β多样性（beta diversity）及其嵌套性与替代型β组分，以探究环境与空间驱动因子的相对重要性。多元回归分析结果显示，生物地理因子与气候因子对α和γ多样性具有显著影响；而空间因子（尤其是岛屿数量、岛间距离与面积跨度）则是解释β多样性变化的关键。结构方程模型进一步表明，γ多样性主要通过其多样性组分（尤其是β多样性）受到间接非生物因子的调控。该结果凸显了β多样性与岛屿空间配置对于理解岛屿生态学与进化过程的重要性。本研究的方法框架可被更广泛地应用于其他生物类群与类群岛系统，为解析生物多样性的起源与维持机制提供全新研究思路。