Intraspecific variability and species turnover drive variations in Collembola body size along a temperate-boreal elevation gradient

Investigating functional facets of biodiversity across elevation gradients provides the perspective to deepen understanding of the response of communities to global changes. Functional ecology approaches typically assume that filtering of traits across broad environmental gradients is largely due to species turnover rather than intraspecific trait variability. However, few studies quantified the relative importance of species turnover versus intraspecific variability for the composition of soil animal communities across environmental gradients. Here, for the first time, we investigated the relative contribution of species turnover, intraspecific trait variability and their covariation to changes in Collembola body size based on measurements at the individual level along a temperate -boreal elevation gradient in northeastern China. The results indicated that community weighted mean (CWM) body size of Collembola varied significantly with elevation as well as with life form, with the variations in CWM body size in total, epedaphic and hemiedaphic species being similar and more pronounced than in euedaphic Collembola. These variations in body size were driven to a similar extent by intraspecific trait variability and species turnover, with the former being somewhat higher in total, epedaphic and euedaphic but not in hemi-edaphic Collembola. Further, variations in body size were better explained by local habitat-related soil factors than by temperature, but the relative importance of these factors differed among ecological groups of Collembola. Overall, these findings show that intraspecific variations in traits may be of similar importance than the turnover of species and needs closer consideration when using trait approaches to understand biodiversity - ecosystem functioning relationships in face of global change.