Island faunas can be characterized by gigantism in small animals and dwarfism in large animals, but the extent to which this so-called ‘island rule’ provides a general explanation for evolutionary trajectories on islands remains contentious. Here we use a phylogenetic meta-analysis to assess patterns and drivers of body size evolution across a global sample of paired island–mainland populations of terrestrial vertebrates. We show that ‘island rule’ effects are widespread in mammals, birds and reptiles, but less evident in amphibians, which mostly tend towards gigantism. We also found that the magnitude of insular dwarfism and gigantism is mediated by climate as well as island size and isolation, with more pronounced effects in smaller, more remote islands for mammals and reptiles. We conclude that the island rule is pervasive across vertebrates, but that the implications for body size evolution are nuanced and depend on an array of context-dependent ecological pressures and environmental conditions.

岛屿动物群的特征可能是小动物的巨人症和大型动物的侏儒症，但这种所谓的“岛屿规则”在多大程度上为岛屿上的进化轨迹提供了一般解释仍然存在争议。在这里，我们使用系统发育荟萃分​​析来评估全球成对岛屿 - 大陆陆生脊椎动物种群样本中体型进化的模式和驱动因素。我们表明，“岛屿统治”效应在哺乳动物、鸟类和爬行动物中普遍存在，但在两栖动物中不太明显，它们大多倾向于巨人症。我们还发现，岛屿侏儒症和巨人症的严重程度受气候、岛屿大小和与世隔绝的影响，对哺乳动物和爬行动物来说，在更小、更偏远的岛屿上影响更明显。我们得出结论，岛屿规则在脊椎动物中普遍存在，