Impact of landscape fragmentation and climate change on body size variation of bumblebees during the last century

Body size is a key parameter of organism fitness. While the impact of climate change on body size has received increasing attention, the long-term consequences of landscape fragmentation are still poorly known. These two major global threats may potentially induce opposite trends: the decrease of body size in warmer environments (e.g. individuals developing faster) or the selection of larger individuals in fragmented habitats (e.g. large individuals more capable of reaching distant patches). We assessed the relationship between temperature and landscape fragmentation with mean body size during the last century, within four European regions (Austria, Belgium, England and above the Arctic circle in Scandinavia) and among queens of five bumblebee species. At the regional scale, we first analysed the variation over time of body size and the two hypothesised drivers, temperature and landscape fragmentation. Then, at the local landscape scale, we tested whether body size varied according to t...