Small mammal diversity and community structure exhibit congruent hump-shaped patterns along a subtropical elevational gradient

Incomplete elevational sampling in studies of biodiversity and community assembly along elevational gradients can result in inconsistent findings and potentially inaccurate conclusions about assembly mechanisms. In this study, we conducted extensive sampling of small mammals over a 3200 m elevational gradient on Xiling Snow Mountain, Southwestern China. We integrated functional and phylogenetic diversity to determine the mechanisms structuring small mammal assemblages. Our findings indicate that taxonomic, functional, and phylogenetic diversity, along with all species richness-corrected indices of functional and phylogenetic diversity, exhibit similar hump-shaped patterns. Our results suggest that environmental filtering plays a considerable role in structuring small mammal communities at low and high elevations, while competitive exclusion governs the assembly processes at middle elevations. Human footprint, Normalized Difference Vegetation Index, precipitation seasonality and potential evapotranspiration are key drivers of small mammal diversity and community structure along elevational gradients. In summary, our study provides evidence that phylogenetic diversity is a robust surrogate for functional diversity, and challenges the recent large-scale studies that advocate a linear relationship between small mammal assembly process and elevation. We emphasize the importance of continuously documenting general patterns of small mammal diversity across entire elevational gradients in future studies.