Mountain gradients distributed across the globe provide a powerful system for understanding the underlying causes of biodiversity gradients. Global characterization of elevational biodiversity gradients have to date focused primarily on patterns of species richness, thus missing information regarding ecosystem functioning. Consequently, a general understanding of the processes involved in the assembly and maintenance of biodiversity is still lacking. Here, we present global characterization of elevational gradients in avian functional diversity, average functional distinctness, and trait-based assemblage composition. We combined expert information on lateral distributions for all birds with a new global compilation of mountain-range-specific data on elevational limits and species’ trait information. To characterize elevational gradients, we fitted the models in a Bayesian framework using INLA.
Results/Conclusions
We found that functional diversity declined with elevation, though that decline was steeper for mountain systems with higher mean annual Net Primary Productivity and mean temperature. Local and global functional distinctness increased with elevation, and that increase was steeper for mountain systems with higher mean annual Net Primary Productivity, smaller area, and lower species richness. Individual dietary and foraging traits showed contrasting elevational gradients, with birds having granivorous and scavenging diets increasing towards higher elevations and all other dietary groups declining. Assemblage average body mass showed a humped elevational pattern.