Connectivity As a Driver of Biodiversity and Functioning in Riverine Landscapes: A Dynamic, Graph Theoretic Approach.

Connectivity is a crucial property of the riverine landscape. Reduction of connectivity, i.e. habitat fragmentation and isolation effects, impacting ecological functions and biotic communities, is one of the most critical threats to river-floodplain systems. Using a graph theoretical approach for analyzing possible transport pathways in the system (directed, undirected, overland, seepage), we could show that essential ecological functions related to sediment composition and quality, hydrochemical conditions, and macrophyte coverage can be predicted and importance of waterbodies in the network and their main connectivity deficits can be identified. In a second step we are now integrating biotic communities in the predictive framework. Dependent on dispersal model and habitat preferences the different taxonomic groups show clear pattern i.e. drifting invertebrate organisms are highly driven on directed transport whereas fish as active swimmers are more dependent on connectivity in the waterbody network or organism with terrestrial or flying dispersal (amphibia or flying insects) are dependent on overland connectivity. Further they interact with the ecological functions in the system. Using a temporal dataset based on eDNA (environmental DNA) we can further show that ecosystem conditions and distributions of biotic communities are dependent on different transport/movement pathways changing with hydrological conditions (flood to low flow conditions). The dynamic graph theoretic approach can, therefore, be used as an essential tool for prioritizing water bodies for nature-based solutions.