Search

Typology systems are frequently used in applied and fundamental ecology and are relevant for environmental monitoring and conservation. They aggregate ecosystems into discrete types based on biotic and abiotic variables, assuming that ecosystems of the same type are more alike than ecosystems of different types with regard to a specific property of interest. We evaluated whether this assumption is met by the Broad River Types (BRT), a recently proposed European river typology system, that classifies river segments based on abiotic variables, when it is used to group biological communities. We compiled data on the community composition of diatoms, fishes, and aquatic macrophytes throughout Europe and evaluated whether the composition is more similar in site groups with the same river type than in site groups of different river types using analysis of similarities, classification strength, typical species analysis, and the area under zeta diversity decline curves. We compared the performance of the BRT with those of four region-based typology systems, namely, Illies Freshwater Ecoregions, the Biogeographic Regions, the Freshwater Ecoregions of the World, and the Environmental Zones, as well as spatial autocorrelation (SA) classifications. All typology systems received low scores from most evaluation methods, relative to predefined thresholds and the SA classifications. The BRT often scored lowest of all typology systems. Within each typology system, community composition overlapped considerably between site groups defined by the types of the systems. The overlap tended to be the lowest for fishes and between Illies Freshwater Ecoregions. In conclusion, we found that existing broad-scale river typology systems fail to delineate site groups with distinct and compositionally homogeneous communities of diatoms, fishes, and macrophytes. A way to improve the fit between typology systems and biological communities might be to combine segment-based and region-based typology systems to simultaneously account for local environmental variation and historical distribution patterns, thus potentially improving the utility of broad-scale typology systems for freshwater biota., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Rivers are generally considered critical habitats for biodiversity; however, this often ignores the fact that many rivers may run dry and support terrestrial as well as aquatic fauna. Here, we investigated the ecological value of intermittent rivers for terrestrial vertebrates by installing camera traps along rivers subject to varying dry periods in two contrasting European climatic zones. We then analysed i) species presence and behaviours (as a proxy of ecological functions) on perennial and intermittent streams; ii) environmental (hydrological and geomorphological) and anthropogenic factors affecting the frequency of occurrence and number of species recorded; and iii) the importance of hydrological factors as regards ecological functioning. In both study areas, we recorded a higher number of species and individuals along intermittent streams than perennial streams, with highest values in intermittent reaches exhibiting shorter dry periods. Both abundance and species richness were strongly affected by hydrological factors in both study areas, including not only the occurrence but also the duration of the dry period. Dry channels played a key role as migration corridors and as a source of food, being used more frequently than riparian habitats when the river ran dry. Our findings indicate that terrestrial vertebrate fauna benefit from dry phases in rivers. Intermittent rivers, supporting a high abundance and diversity of fauna, should be considered as target ecosystems for wildlife conservation. Not doing so will jeopardise urgently needed conservation strategies in the face of accelerating global climate change., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)