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 relationsh...