Changes in ground-dwelling carabid communities and their interactions with the microbiota of selected soil compartments along an Alpine elevational gradient

Global warming is affecting Alpine habitats through an increase in temperature above the global average. Such rapid environmental change may affect biotic interactions and thus ecosystem stability and functionality; however, these pro- cesses in mountain soils are not well understood. We used an elevation gradient ranging from 1000 to 2500 m a.s.l. as a proxy for climate change to investigate the diversity of ground-dwelling car- abid beetle species and selected body traits. We also analysed the microbiota of the beetles and other soil-associated compartments to under- stand the complex interactions and co-occur- rences of microbial communities in alpine soils. On 12 grazed pastures (3 replicate sites every 500 m of altitude), we set up pitfall traps for an entire growing season and emptied them every two weeks. Nearly 6000 individuals were captured and morphologically identified to spe- cies, with body length, wing development and sex recorded. In addition, 182 carabid beetles were collected by hand, and used for microbial community analysis by next-generation sequenc- ing. For comparison, microbiota analyses were also performed on soil, rhizosphere, nematode, collembola, earthworm and vertebrate faecal samples. Community composition and diversity of carabids changed significantly with elevation, but not in a linear pattern. Especially the prokaryotic commu- nities in carabid beetles showed trophic related patterns. Compared to the other soil-associated compartments, bacterial and fungal alpha and beta diversity in carabids was very low and few taxa were shared. Our data confirm ecological patterns along elevation and provide a first insight into the complex interactions between soil, faunal and microbial players.