Higher predicted climate-change vulnerability for spring-dwelling freshwater biota

Environmental change threatens freshwater biodiversity through altered temperature and precipitation patterns. Available data is frequently insufficient to determine impacts at the species level leading to misinterpreted species' vulnerability. Conversely, phylogenetic relationships, current distributions and ecological traits of the caddisfly subfamily Drusinae are well known. Thus, species distribution models (SDMs) were set up for 47 Drusinae species to assess individual and trait-specific climate change (CC) vulnerability. Species were grouped by larval feeding guild, stream zonation preference and level of endemism. Models were calibrated with predictors describing climate, topography and geology at a spatial resolution of 1 km² and were projected for five general circulation models under four future climate scenarios. To limit dispersal, distribution projections were restricted to a maximum of 500 km until the year 2080. Relative predicted range change fluctuated between -100% and 197%, with extinction predicted for five species. Altitudinal shifts varied between -2% and +15%, with distribution centroids shifting between 28 km and 119 km. Our results identify stream zonation, a non-phylogenetic trait, as the best indicator of CC vulnerability. Furthermore, two important conclusions are highlighted: monitoring is best done at the species level while the biodiversity of springs and low order streams requires considerably more attention.