Data from: The island-mainland species turnover relationship

Many oceanic islands are notable for their high endemism, suggesting that islands may promote unique assembly processes. However, mainland assemblages sometimes harbour comparable levels of endemism, suggesting that island biotas may not be as unique as often assumed. Here, we test the uniqueness of island biotic assembly by comparing the rate of species turnover among islands and the mainland, after accounting for distance decay and environmental gradients. We modeled species turnover as a function of geographic and environmental distance for mainland (M-M) communities of Anolis lizards and Terrarana frogs, two clades that have diversified extensively on Caribbean islands and the mainland Neotropics. We compared mainland-island (M–I) and island-island (I–I) species turnover to predictions of the M–M model. If island assembly is not unique, then the M–M model should successfully predict M–I and I–I turnover, given geographic and environmental distance. We found that M–I turnover and, to a lesser extent, I–I turnover were significantly higher than predicted for both clades. Thus, in the first quantitative comparison of mainland–island species turnover, we confirm the long-held but untested assumption that island assemblages accumulate biodiversity differently than their mainland counterparts.许多大洋岛屿以极高的特有性（endemism）为显著特征，这表明岛屿可能催生独特的生物群落组装过程。然而，大陆生物群落有时也拥有相当水平的特有性，这提示岛屿生物区系或许并不像人们通常认为的那般独特。本研究通过对比岛屿与大陆间的物种周转（species turnover）速率，并纳入距离衰减（distance decay）与环境梯度（environmental gradients）的影响因素，检验岛屿生物组装过程的独特性。我们以安乐蜥（Anolis）与Terrarana蛙类的大陆（M-M）群落为研究对象，将物种周转速率建模为地理距离与环境距离的函数；这两个支系均在加勒比群岛与新热带大陆经历了广泛的物种分化。我们将大陆-岛屿（M-I）与岛屿-岛屿（I-I）的物种周转速率与M-M模型的预测结果进行比对。若岛屿生物组装过程并非独特，则在考虑地理与环境距离的前提下，M-M模型应能准确预测M-I与I-I的物种周转情况。我们发现，两个支系的M-I周转速率均显著高于模型预测值，而I-I周转速率的超出幅度相对较小。因此，在首次针对大陆-岛屿物种周转的定量对比研究中，我们验证了这一长期存在但尚未经实证的假设：岛屿生物群落积累生物多样性的方式与大陆群落存在显著差异。