Trait variation and functional trait space of arthropods along different elevation sites in Italy

Understanding how species and communities have adapted to increasing elevation is crucial for predicting species responses to climate change and for informing conservation strategies. We first investigated how four key functions—nutrition, reproduction, dispersion, and organism size—varied. Next, we analyzed the community trait space of four arthropod groups across four elevations ranging from 1,000 m to 2,500 m above sea level in the Vinschgau Valley, Northern Italy. Results on individual trait variation differed among groups and were significant only in some cases. Body size tended to increase at higher elevations for orthopterans, ants, and carabid beetles. For nutrition, we observed a tendency toward more carnivorous species with increasing elevation. Dispersal potential tended to be higher at lower elevations, and reproductive potential also seemed to be higher at low elevations for butterflies and carabid beetles. Second, we performed a joint analysis of all four traits as community trait space, which revealed distinct patterns for each group. Orthopterans and butterflies showed a significant reduction in trait space at higher elevations, whereas ants and partly carabid beetles demonstrated a significant increase. The overlap in trait space between adjacent elevation sites (indicating similarity in community composition) was significantly higher at lower elevations for carabid beetles and butterflies, and at higher elevations for ants, and partly for orthopterans. Our research indicates that adaptations to increasing elevation vary across the four groups within the same phylum. From a conservation perspective, our results suggest that some taxa, such as orthopterans, are particularly vulnerable at higher elevations, while others, such as ants, are more susceptible to climate change at low elevations. The analysis of trait space provides a nuanced understanding of how communities assemble and vary functionally along elevational gradients and may help to identify areas where insect communities are at risk of acute and rapid species loss in the future.