Temporal turnover in species' ranks can explain variation in Taylor's slope for ecological timeseries

The scaling exponent relating the mean and variance of the density of individual organisms in space (i.e., Taylor's slope: z_space) is well studied in ecology, but the analogous scaling exponent for temporal datasets (z_time) is underdeveloped. Previous theory suggests the narrow distribution of z_time (e.g., typically 1–2) could be due to interspecific competition. Here, using 1694 communities time series, we show that z_time can exceed 2, and reaffirm how this can affect our inference about the stabilizing effect of biodiversity. We also develop a new theory, based on temporal change in the ranks of species abundances, to help account for the observed z_time distribution. Specifically, we find that communities with minimal turnover in species' rank abundances are more likely to have higher z_time. Our analysis shows how species-level variability affects our inference about the stability of ecological communities.