| Description |
Climate change induces unprecedented dry periods in previously perennial streams, significantly impacting aquatic macroinvertebrate metacommunities. We assumed that the historical (i.e., several dozens of years) patterns of presence or absence of drying in dry river networks (DRNs) modifies the relative importance of local and regional, spatial, and niche-related environmental factors in metacommunity organisation. In this study, we sampled Trichoptera metacommunities in three Drying River Networks (DRNs) along a latitudinal gradient across three countries, also representing a drying gradient. In Croatia, drying has been present in the DRN for a very long time, with an almost constant annual occurrence. At the other end of the scale is the Hungarian DRN, where the drying has appeared in recent years and with varying spatial and temporal annual intensity, but is becoming more and more intense, while the drying history of the Czech DRN lies between these two with highly unpredictable occurrences. Here, we hypothesised that the relevance of spatio-temporal connectivity differs according to the historical drying patterns in each catchment. In 2021, the Trichoptera metacommunities were sampled six times bimonthly at 20–25 sites per DRN, and a comprehensive set of local and regional environmental parameters were recorded. Spatial variables were generated through Moran’s eigenvector maps (MEM) and asymmetric eigenvector maps (AEM) from watercourse distances among sites in each river network. Spatio-temporal connectivity was assessed using the STcon framework, and values were calculated for different time frames (for 30, 200, 365, 730, 1825, and 3650 days before sampling). We analysed the relative relevance of spatial (MEM and AEM), niche, and spatiotemporal (STcon) drivers of these communities by means of hierarchical variance partitioning. The explanatory power of the STcon was the highest in the Hungarian DRN and the lowest in Croatia, with significant differences observed across different time frames. In the Hungarian DRN, the connectivity calculated for time frames shorter than one year proved to be the most relevant factor, while in the case of the Croatian DRN, the five- and ten-year-long connectivity hold the greatest explanatory power. These findings underscore the pivotal role of spatiotemporal connectivity in shaping metacommunities, albeit with varying impacts across river basins characterised by different drying histories. Such insights are critical for understanding and managing the ecological ramifications of climate-induced alterations in aquatic ecosystems. This work was supported by the EU-funded DRYvER project (869226).
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