Hyperspectral imagery, LiDAR point clouds, and environmental DNA to assess land-water linkage of biodiversity across aquatic functional feeding groups

Functional feeding groups (FFGs) are key components sustaining ecosystem functioning in riverine ecosystems. Their distribution and diversity are tightly associated with surrounding terrestrial landscape through land-water linkages. Nevertheless, knowledge about the spatial extent and magnitude of these cross-ecosystem linkages within major FFGs still remains unclear. Here, we conducted an airborne imaging spectroscopy campaign and a systematic environmental DNA (eDNA) field sampling of river water in a 740-km² mountainous catchment, combined with light detection and ranging (LiDAR) point clouds, to obtain the spectral and morphological diversity of terrestrial landscape and the diversity of major FFGs in rivers. We identified the scale of these linkages ranging from a few hundred meters to more than 10 km, with collectors and filterers, shredders, and small invertebrate predators having local-scale association, while invertebrate eating fish, grazers and scrapers having more regional-scale associations. Among all major FFGs, shredders, grazers and scrapers in the streams had the strongest association with surrounding terrestrial vegetation. Our research reveals the reference spatial scales at which major FFGs are in relation to surrounding terrestrial landscape, providing spatially explicit evidence of the cross-ecosystem linkages needed for conservation design and management.