Cristina Mariana Jacobi , Tadeu Siqueira

The temporal stability of ecological properties tends to increase with spatial scale and levels of biological organization, which is mostly associated with deterministic processes. However, random fluctuations caused by demographic stochasticity in small populations might extend to communities and metacommunities, potentially affecting stability propagation across biological levels and spatial scales. Here, we tested this hypothesis by combining process-based simulations and statistical modeling of 468 sites distributed across 39 regions, sampled from 1981 to 2019, to investigate how fish communities and metacommunities changed over time at local and regional scales. We found that species-rich communities in highly seasonal environments were more variable. However, the major driver of compositional temporal variability was community size. Communities comprising smaller populations were more temporally variable than those comprising larger populations. This relationship was weaker at the regional scale, suggesting a dampening effect at the metacommunity level. Our results suggest that the potential effects of demographic stochasticity, which are undoubtedly stronger in small populations, might extend beyond populations, leaving different signals in the temporal variability of ecological properties. These effects appear to be stronger and consistent within small communities and weaker in metacommunities. Our study advances the knowledge of how populational-demographic stochasticity might affect biodiversity temporal dynamics across scales.