The island species area relationship (ISAR) is an important tool for measuring variation in species diversity in variety of insular systems, from true-island archipelagoes to fragmented terrestrial landscapes. However, it suffers from several limitations. For example, due to the sample-area effect, positive relationships between species and area cannot be directly interpreted as evidence for deterministic effects of area per se. Additionally, richness-based analyses may obscure species-level responses to area and isolation that may better inform conservation practice. Here, we use random placement models to control for variation in abundance, occupancy and richness associated with the sample-area effect, allowing deterministic effects of area and isolation, and how they vary with species' functional traits, to be resolved using linear mixed effects models. We demonstrate the utility of this approach using a butterfly assemblage persisting on a naturally fragmented landscape of lake islands. The ISAR did not significantly deviate from random placement in relation to island area, isolation or habitat diversity, supporting stochastic assembly consistent with the sample-area effect. Such inferences support the habitat amount hypothesis, which prioritizes preserving the maximum amount of habitat irrespective of its degree of fragmentation. However, species-level analyses demonstrated that species' abundances were significantly lower on both smaller and more isolated islands than what is predicted by the sample-area effect. Moreover, effects of area per se were significantly greater for smaller, less mobile and rare species. Species' occurrences also significantly deviated from predictions of the sample-area effect in relation to island isolation. Thus, our approach illustrates that richness-based analyses not only result in incorrect inferences on mechanisms underlying ISARs, but also obscure important effects of area per se and isolation on individual species that vary with functional traits. We therefore suggest that these effects should not be solely inferred from richness-based analyses, but rather evaluated on a species-by-species basis.

中文翻译：

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区分面积本身的影响以及与真实岛屿和栖息地碎片的样本面积效应的隔离

岛屿物种面积关系 (ISAR) 是测量各种岛屿系统中物种多样性变化的重要工具，从真正的岛屿群岛到破碎的陆地景观。然而，它受到一些限制。例如，由于样本面积效应，物种和面积之间的正相关不能直接解释为面积本身确定性效应的证据。此外，基于丰富度的分析可能会掩盖物种对区域和隔离的反应，这可能会更好地为保护实践提供信息。在这里，我们使用随机放置模型来控制与样本区域效应相关的丰度、占有率和丰富度的变化，允许区域和隔离的确定性效应，以及它们如何随物种的功能特征而变化，使用线性混合效应模型解决。我们使用蝴蝶组合展示了这种方法的实用性，这些蝴蝶组合在湖泊岛屿的自然破碎景观上持续存在。ISAR 没有显着偏离与岛屿面积、隔离或栖息地多样性相关的随机放置，支持与样本区域效应一致的随机组装。这些推论支持栖息地数量假设，即优先保护最大数量的栖息地，而不管其破碎程度如何。然而，物种水平的分析表明，在更小和更孤立的岛屿上，物种的丰度显着低于样本面积效应所预测的。此外，面积本身对较小、流动性较差和稀有物种的影响要大得多。物种' 发生的事件也大大偏离了与岛屿隔离有关的样本面积效应的预测。因此，我们的方法表明，基于丰富度的分析不仅会导致对 ISAR 机制的错误推断，而且还会掩盖面积本身和隔离对因功能特征而异的个体物种的重要影响。因此，我们建议不应仅从基于丰富度的分析中推断出这些影响，而应在逐个物种的基础上进行评估。但也掩盖了面积本身和隔离对因功能性状而异的个体物种的重要影响。因此，我们建议不应仅从基于丰富度的分析中推断出这些影响，而应在逐个物种的基础上进行评估。但也掩盖了面积本身和隔离对具有不同功能特征的个体物种的重要影响。因此，我们建议不应仅从基于丰富度的分析中推断出这些影响，而应在逐个物种的基础上进行评估。