An aquatic and terrestrial coupling lens of drying on inland water ecosystems: a functional trait-based assessment

Drying events are ecological drivers in temporary inland waters, where hydrological variability influences aquatic and terrestrial invertebrate communities. While taxonomic responses to drying have been studied, functional responses remain poorly understood. We investigated taxonomic richness, functional diversity, and trait composition respond to drying across aquatic and terrestrial (spiders and ants) invertebrates, the latter distinguishing shoreline/dry bed and riparian communities. We studied temporary lotic (streams) and lentic (lakes) ecosystems, considering hydrological phases: wet, contraction, and dry. In lotic ecosystems, taxonomic and functional metrics of aquatic communities increased from the wet to the contraction phase. In contrast, lentic ecosystems showed a decline in taxonomic and functional metrics in the contraction phase compared to the other phases. For aquatic invertebrates, ecosystems showed trait shifts, with traits linked to flowing and aquatic respiration replaced by those adapted to stagnant conditions and aerial respiration as drying progressed. For spiders, taxonomic richness and functional diversity increased along drying in shoreline habitats, but remained stable in riparian zones. Spider shoreline assemblages shifted from web-building and vegetation-associated traits to active hunting and ground-dwelling strategies along drying ant assemblages showed no consistent responses. These findings highlight how trait-based approaches improve our understanding of biodiversity responses to drying.