The species-area relationship (SAR) has over a 150-year-long history in ecology, but how its shape and origins vary across scales and organisms is still not fully understood. This is the first subcontinental freshwater study to examine both properties of the SAR in a spatially explicit way across major organismal groups (diatoms, insects, and fish), differing in body size and dispersal capacity. First, to describe the SAR shape, we evaluated the fit of three commonly used...