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，却忽略了绝大多数岛屿在空间上嵌套于群岛之中这一事实。本研究采用截然不同的研究范式，聚焦于整个群岛系统：我们收集了全球23个群岛及其包含的174个组成岛屿的维管植物 (vascular plants) 物种丰富度 (species richness) 数据。我们评估了多种因素对植物多样性的差异化影响：包括生物地理因子 (biogeographic factors)（岛屿面积、隔离度 (isolation)、形成年代 (age)、海拔 (elevation)）、当前与古气候条件（温度 (temperature)、降水量 (precipitation)、季节节律 (seasonality)、气候变化速率 (climate change velocity)），以及群岛内部空间结构 (intra-archipelagic spatial structure)（群岛总面积 (archipelago area)、岛屿数量 (number of islands)、面积跨度 (area range)、连通性 (connectivity)、环境容积 (environmental volume)、岛间距离 (inter-island distance)）。我们将每个群岛的物种多样性 (γ多样性，γ diversity) 加法分解为α多样性 (α diversity)、β多样性 (β diversity) 及其嵌套组分 (nestedness) 与物种更替组分 (replacement β-components)，以探究环境与空间驱动因子的相对重要性。多元回归分析 (multiple regressions) 结果显示，生物地理因子与气候因子对α多样性和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多样性变化的关键因素。结构方程模型 (structural equation models) 进一步表明，γ多样性主要通过其多样性组分受到间接非生物因子的调控，其中尤以β多样性的作用最为突出。这一研究结果凸显了β多样性与岛屿空间排布对于理解岛屿生态学 (insular ecology) 与演化过程的重要性。本研究提出的方法论框架可被广泛应用于其他类群 (taxa) 及类群岛系统，为揭示生物多样性 (biodiversity) 的起源与维持机制提供全新的研究视角。