Biotic Variability and Synchrony Across Hierarchical Levels and Freshwater Networks

Understanding temporal variability and synchrony across biological hierarchical levels (from species to metacommunities) and ecosystems, and their underlying drivers, remains a fundamental ecological question. However, most studies are performed within an ecosystem, overlooking the complexity structuring natural high-level metacommunities across ecosystems. By applying theoretical frameworks of metacommunity variability with phytoplankton datasets across a pond-stream-lake continuum, we show that (i) temporal variability decreases from species to metacommunities, while synchrony exhibits complex hierarchical patterns and varies depending on spatial scales; (ii) temporal variability and synchrony are lower in streams than in ponds or the lake, and spatiotemporal community-environment relationships are stronger in the lake than in the ponds or streams. These patterns are strongly related to environmental fluctuations, dispersal and species diversity. Our study advances the theoretical and empirical understanding of how complex biological hierarchies and freshwater networks influence biotic variability and synchrony, providing valuable insights for aquatic biodiversity conservation.