| Description |
Spatial connectivity varies temporally due to fragmentation caused by drying and may potentially define the diversity and composition of communities. We studied spatiotemporal patterns in three drying river networks (DRNs) in Croatia, Czechia and Hungary, with varying drying patterns, focusing on the roles of local environmental variables and regional influences. We aimed to assess how variation in spatiotemporal connectivity (STcon) influenced metacommunity structure and dynamics, contributing to our understanding of rapidly changing aquatic ecosystems under climate change. We used a unique hydrological dataset with a novel approach to quantify spatiotemporal connectivity across three DRNs spanning different time windows (30, 200, 365, 730, 1825 and 3650 days before sampling). These values summarised how much drying each site had been exposed to at different time scales. Then, we estimated the correlation between these STcon values and local (i.e., environmental variables) and regional (i.e., spatial arrangement) metrics using hierarchical variance partitioning. Local environmental variables were consistently strongly associated with drying patterns, with regional influences playing a secondary but important role. Both local and regional-scale variables showed similar patterns across all DRNs. STcon values were also significantly associated with metacommunity assembly, but, in contrast, differences in drying patterns altered the relative importance of STcons calculated for different time windows across the DRNs. The DRN in Croatia, with consistent seasonal drying, was markedly influenced by long-term STcon (730, 1825 and 3650-day time windows). The DRN in Hungary experienced more recent and irregular drying, and exhibited associations with short-term STcon (200-day time window), whereas the DRN in Czechia was positioned in between, showing a less clear association with spatiotemporal connectivity. This study concluded that although local environmental variables were most strongly associated with caddisfly metacommunities, the role of spatiotemporal connectivity, particularly in the context of drying trends, was also marked. This was particularly evident from long-term drying patterns at the catchment scale in DRNs with a longer history of permanence where recent drying may have had a stronger impact. Thus, climate change-induced drying might be reshaping metacommunity dynamics, with varying impacts depending on historical drying patterns in the DRNs. This research demonstrates the need to consider both spatial and temporal patterns and processes to better understand current diversity trends. The incorporation of long-term drying trends will improve understanding of the ways in which global climate change pressures might reshape aquatic communities and the functioning of these essential ecosystems.
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