Differences between space and time in biodiversity
The largest difference between spatial and temporal beta diversity was the property of the species pool. In the spatial context, if an observer moves sufficiently far from one location to a different region, the composition of the species pool will differ, and eventually, there will be no common species between the first and the second place; thus, the value of spatial beta diversity reaches 1. In contrast, in a temporal context, if it is not assumed that the composition of the species pool changes over time, it is rare to have a situation where common species are completely absent from the species composition at the outset. Surely, in evolutionary time scale, the species pool would gradually change, but at the ecological time scale (e.g. less than a hundred years), dramatic changes in the species pool should not be hypothesised as a normal condition. However, the influence of recent climate change and other anthropogenic disturbances will change the composition of the species pool through species distributional shifts (Dornelas et al., 2014; Koide, Yoshikawa, Ishihama, & Kadoya, 2022). Therefore, these influences would increase the upper limits of temporal beta diversity. The present study focused only on neutral dynamics to understand the fundamental properties of temporal beta diversity. However, in the future, more complex models should be studied to understand the influence of climate change and other anthropogenic disturbances.