Data from: Functional and phylogenetic dimensions of tree biodiversity reveal unique geographic patterns

Aim: Quantify tree functional and phylogenetic richness and divergence at
the global scale, and explore the drivers underpinning these biogeographic
patterns. Location: Global Time Period: Present Major taxa studied:
Trees  Methods: Using global tree occurrence data, we outlined
species’ observed ranges using individual alpha hulls to obtain per-pixel
tree species composition. Using eight traits from a recent tree-trait
database and a vascular-plant phylogeny we computed and mapped four pixel
level biodiversity indices, including two metrics related to richness:
phylogenetic richness and functional richness and two related to
divergence: mean pairwise phylogenetic distance and Rao's quadratic
entropy. To account for the effect of species richness, we also calculated
standardized effect sizes accounting for richness for each pixel. We then
explored the relations between richness and divergence and the latitudinal
patterns of divergence both globally and across biomes. Finally, we used a
random forest modeling approach to test for drivers of the different
dimensions of diversity in trees. Results: In contrast to the latitudinal
gradient in species richness, functional and phylogenetic divergence both
peak in mid-latitude systems, exhibiting the highest values in temperate
ecosystems and lowest values in boreal and tropical forests. This result
holds for functional divergence when removing gymnosperms but the peak
flattens for phylogenetic divergence. Phylogenetic richness is
consistently lower than expected given the number of species, whereas
functional richness has higher-than-expected values at mid-latitudes,
mimicking functional divergence patterns. When considering the drivers of
these diversity patterns, temperature and historical speciation rates
consistently emerge as the strongest forces driving divergence, with
negligible effects of human influence, soils or historical climate
stability. Main Conclusions: Collectively, these results reveal unique
similarities and disparities across biomes that are not apparent in any
single dimension of biodiversity, highlighting the importance of
considering multiple aspects of biodiversity in the management of natural
ecosystems.