Biogeographical variation of angiosperm taxonomic traits exhibits a globally consistent structure

The global biogeography of angiosperm traits shows complex spatial variation. Although the geography of individual taxonomic traits has been described, whether their proportions spatially covary to define consistent dimensions of regional composition remains unexplored. Here we analysed the biogeographical patterns of 15 traits derived from over 320,000 species, revealing a globally consistent, low-dimensional structure whose primary dimensions are associated with hydrothermal environmental gradients and regional phylogenetic structure. The first dimension captures a gradient from woody, evergreen, fleshy-fruited plants in warm, wet climates to herbaceous, dry-fruited plants in cooler or drier regions. The second dimension highlights the prevalence of zygomorphic, sympetalous and bisexual flowers, together with annual life cycles, in warm but arid environments. Within-region trait divergence peaks near the median of the first dimension and increases along the second. Although environmental gradients help explain these coordinated spatial patterns, associations with regional phylogenetic structure strengthen from the first to the second dimension. In arid regions, phylogenetic clustering is consistent with the preferential representation of lineages bearing water-limitation trait syndromes. By identifying these primary dimensions, our study advances the field beyond cataloguing disparate patterns toward a more integrated and generalizable understanding of global angiosperm biogeography.