Climate change and elevational range shifts: evidence from dung beetles in two European mountain ranges

Aim: Mountain regions are particularly well-suited for investigating the impact of climate change on species ranges because they encompass both upper and lower limits of species distribution. Here, we investigate changes in the elevational distribution of dung beetle species (Coleoptera: Scarabaeoidea) in two separate mountain regions in Europe. Location: South-western Alps (France) and Sierra Nevada (Spain). Methods: We compared historical and current data on dung beetle distributions along elevation gradients for 30 species in the SW Alps and 19 species in the Sierra Nevada. We tested for significant changes between survey periods in three parameters: mean elevation and upper and lower range limits. Results: We found up-slope range shifts for 63% and 90% of the species in the SW Alps and Sierra Nevada, respectively. Up-slope range shifts resulted mainly from expansion of upper range limits in the SW Alps and from changes of both range limits in the Sierra Nevada. The magnitudes of range shifts were consistent with the level of warming experienced in each region, but they also reflected the asymmetrical warming observed along the elevation gradients. Smaller changes were observed for species reaching their historical range limits at the higher elevations, associated with a non-significant increase in temperature between periods. Main conclusions: The differences observed between regions are related to the geographical position of each mountain range, which determines the characteristics (including thermal tolerance) of the regional species pool, and the level of warming, which determines whether maximum thermal tolerance has been exceeded for the majority of species in the region. Our results highlight the importance of considering both the biogeography of the mountain and the species pool under study when assessing the sensitivity of species to future climate change in mountain regions.