AIM: We tested whether species–area relationships of small islands differ among plant growth forms and whether this influences the prevalence of the small‐island effect (SIE). The SIE states that species richness on small islands is independent of island area or relates to area in a different way compared with larger islands. We investigated whether island isolation affects the limits of the SIE and which environmental factors drive species richness on small islands. LOCATION: Seven hundred islands (< 100 km²) worldwide belonging to 17 archipelagos. MAJOR TAXA STUDIED: Angiosperms. METHODS: We applied linear and breakpoint species–area models for angiosperm species richness and for herb, shrub and tree species richness per archipelago separately, to test for the existence of SIEs. For archipelagos featuring the SIE, we calculated the island area at which the breakpoints occurred (breakpoint area) and used linear models to test whether the breakpoint areas varied with isolation. We used linear mixed‐effect models to discern the effects of seven environmental variables related to island area, isolation and other environmental factors on the species richness of each growth form for islands smaller than the breakpoint area. RESULTS: For 71% of all archipelagos, we found an SIE for total and herb species richness, and for 59% for shrub species richness and 53% for tree species richness. Shrub and tree species richness showed larger breakpoint areas than total and herb species richness. The breakpoint area was significantly positively affected by the isolation of islands within an archipelago for total and shrub species richness. Species richness on islands within the range of the SIE was differentially affected by environmental factors across growth forms. MAIN CONCLUSION: The SIE is a widespread phenomenon that is more complex than generally described. Different functional groups have different environmental requirements that shape their biogeographical patterns and affect species–area and, more generally, richness–environment relationships. The complexity of these patterns cannot be revealed when measuring overall plant species richness.

中文翻译：

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小岛上的物种-面积关系因植物生长形式而异

目的：我们测试了小岛的物种-面积关系是否因植物生长形式而异，以及这是否会影响小岛效应 (SIE) 的流行。SIE 指出，与大岛屿相比，小岛屿上的物种丰富度与岛屿面积无关或以不同的方式与面积相关。我们调查了岛屿隔离是否会影响 SIE 的极限，以及哪些环境因素驱动了小岛上的物种丰富度。位置：全球七百个岛屿（< 100 平方公里），属于 17 个群岛。研究的主要分类群：被子植物。方法：我们分别对每个群岛的被子植物物种丰富度和草本、灌木和乔木物种丰富度应用线性和断点物种-面积模型，以测试 SIE 的存在。对于以 SIE 为特色的群岛，我们计算了断点发生的岛屿面积（断点面积），并使用线性模型来测试断点面积是否随隔离而变化。我们使用线性混合效应模型来辨别与岛屿面积、隔离和其他环境因素相关的七个环境变量对小于断点面积的岛屿的每种生长形式的物种丰富度的影响。结果：对于 71% 的群岛，我们发现总和草本物种丰富度的 SIE，灌木物种丰富度的 SIE 为 59%，乔木物种丰富度的 SIE 为 53%。灌木和乔木物种丰富度显示出比总和草本物种丰富度更大的断点区域。断点区域受到群岛内岛屿总和灌木物种丰富度隔离的显着积极影响。SIE 范围内岛屿上的物种丰富度受不同生长形式的环境因素的影响不同。主要结论：SIE 是一种普遍现象，比一般描述的更复杂。不同的功能群有不同的环境要求，这些要求塑造了它们的生物地理模式并影响物种-面积，更一般地说，影响了丰富度-环境关系。 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 在测量整体植物物种丰富度时，无法揭示这些模式的复杂性。更一般地说，丰富度与环境的关系。在测量整体植物物种丰富度时，无法揭示这些模式的复杂性。更一般地说，丰富度与环境的关系。在测量整体植物物种丰富度时，无法揭示这些模式的复杂性。