Data from: Sampling effects drive the species-area relationship in lake zooplankton

The Island Species-Area relationship (ISAR) describes how the numbers of species increases with increasing size of an island (or island-like habitat, such as lakes), and is one of the oldest laws in ecology. Despite its conceptual importance, there remains a great deal of ambiguity regarding the ISAR and its underlying processes. We compiled data from sampled zooplankton assemblages from several hundred lakes in North America and Europe to examine the influence of the three main hypothesized mechanisms leading to ISARs - passive sampling, disproportionate effects, and habitat heterogeneity. We compiled data on lake zooplankton assemblages that reported sample-level and lake level species richness estimates, as well as relative abundance data. In both North American and European lakes, we found a consistent and strong increase in total species richness with increasing lake area. However, when we compared the number of species standardized by number of individuals, there was no relationship between lake area and sample-level species richness or an estimate of species relative abundances, calculated as the Probability of Interspecific Encounter (PIE; a measure of evenness). This was true even when multiple samples were taken across lakes and combined, reducing the likelihood that habitat heterogeneity was driving the results. Overall, our results suggest that the ISAR of zooplankton in these lakes was most likely determined by sampling effects rather than disproportionate effects or habitat heterogeneity leading to more species in larger lakes. Understanding the mechanisms driving ISAR results such as ours can also help us develop predictions for biodiversity change when the area of these habitats changes.

岛屿物种-面积关系（Island Species-Area Relationship, ISAR）阐述了物种数量随岛屿（或类岛屿生境，如湖泊）面积增加而增长的规律，是生态学领域最古老的定律之一。尽管其概念意义重大，但学界对ISAR及其背后的驱动过程仍存在诸多认知模糊之处。我们收集了北美与欧洲数百个湖泊的浮游动物群落采样数据，旨在检验导致ISAR的三大主流假说机制——被动采样效应、不成比例影响与生境异质性。本次研究整理的湖泊浮游动物群落数据，涵盖了采样尺度与湖泊尺度的物种丰富度估计值，以及相对丰度数据。在北美与欧洲的湖泊中，我们均观测到总物种丰富度随湖泊面积增加呈现出稳定且显著的增长趋势。然而，当我们依据个体数量对物种数进行标准化后发现，湖泊面积与采样尺度的物种丰富度，或是以种间相遇概率（Probability of Interspecific Encounter, PIE，一种均匀度度量指标）计算的物种相对丰度估计值之间均无关联。即便我们对多个湖泊的多组采样数据进行合并分析，降低了生境异质性驱动研究结果的可能性，该结论依然成立。总体而言，我们的研究结果表明，上述湖泊中浮游动物的ISAR最有可能由采样效应决定，而非本应使大型湖泊拥有更多物种的不成比例影响或生境异质性。阐明驱动此类ISAR结果的机制，还有助于我们在这类生境面积发生变化时，对生物多样性变化做出预测。