Environmental and evolutionary factors jointly shape life-history trait diversity of terrestrial vertebrates across China.

Life-history traits represent evolutionary adaptations that mediate responses to external environments. Analyzing variation in these traits provides valuable insights into macroecological processes and supports the development of effective conservation and restoration strategies. However, large-scale biogeographic patterns in life-history trait diversity among terrestrial vertebrates remain insufficiently characterized, and the processes shaping these patterns are not well understood. This study integrated life-history and spatial distribution data for 2 334 terrestrial vertebrate species in China, including 398 amphibians, 211 reptiles, 541 mammals, and 1 184 birds, to evaluate spatial patterns of trait diversity and identify underlying drivers. Assemblages in South and Southwest China exhibited high species richness, substantial assemblage-level evolutionary distinctiveness, expanded trait volumes, and elevated trait densities compared to null expectations, indicating roles as both evolutionary museums and cradles. In contrast, assemblages on the Tibetan Plateau showed expanded trait volumes but low trait densities, reflecting niche expansion among limited taxa. These findings emphasize the importance of niche packing before assemblages reach environmental carrying limits. Assemblages with high evolutionary distinctiveness tended to display high trait volumes and low trait densities, suggesting a consistent relationship between phylogenetic structure and functional diversification. Among the four groups, amphibians showed the highest sensitivity to environmental variation, highlighting the need for focused conservation efforts. Overall, this study revealed pronounced spatial heterogeneity in trait diversity across China, shaped by species richness, evolutionary distinctiveness, and environmental variation, providing valuable insights for refining conservation priorities for terrestrial vertebrate taxa.