Temporal beta-diversity patterns are highly dependent on fundamental parameters of neutral dynamics

Abstract

Temporal changes in community composition, known as temporal beta diversity, are a facet of biodiversity change. Macroecological patterns of temporal beta diversity have gained attention due to the recent biodiversity crisis. However, little attention has been paid to how temporal beta diversity differs from spatial beta diversity, and even the most basic neutral dynamics and temporal beta-diversity patterns remain poorly understood. Therefore, this study aimed to reveal the basic properties of temporal beta-diversity under neutral dynamics and to identify how they differ from spatial beta-diversity patterns. A simulation of neutral dynamics was conducted to test the parameter dependency of temporal beta-diversity patterns. Specifically, four fundamental parameters of the neutral model—the fundamental biodiversity number, local community size, mortality rate, and immigration rate—were studied. To describe the form of the simulated temporal distance-decay patterns based on the Bray–Curtis and Sørensen dissimilarity indices, a three-parameter negative exponential function was fitted to each simulated dissimilarity matrix. The negative exponential function was successfully fitted to all the simulated results. The simulated results demonstrated that upper limits exist in the temporal distance-decay patterns; thus, the temporal distance-decay curves saturate before reaching a completely dissimilar state. Additionally, the form of the curve strongly depends on the four parameters of the neutral model. These results, combined with conceptual considerations, suggest that the relationship between local communities and virtual species pools differs between temporal and spatial beta diversity. Specifically, it is hypothesized that the species pool is spatially variable but temporally more constant.