Sampling bias in species observation has challenged biogeographers for many years to precisely quantify macro-scale biodiversity patterns. Based on sample completeness-based standardization, we generated a bias-corrected global species diversity map for woody angiosperms using > 10 million occurrence records.
The highest woody species diversity was identified in central South America followed by western tropical Africa and Indomalayan-Australasian region including the mid latitudinal zone of East Asia.The bias-corrected diversity demonstrated heterogeneous, non-linear latitudinal and longitudinal gradients. The latitudinal diversity gradient in the Americas showed a typical symmetric shape with a peak at the equator and decline toward both poles. The latitudinal diversity gradient in the Africa-Europe region showed a peak at the equator and decline toward higher latitude in the Northern Hemisphere and up to middle latitude in the Southern Hemisphere. The latitudinal diversity gradient in the Asia-Oceania region showed a peak at northern central latitudes. Current climate coupled with paleoclimatic/topographic factors emerged as fundamental drivers in the generation of highly complex biodiversity patterns for woody angiosperms. Notably, at the global scale actual evapotranspiration (AET) was the most important predictor across a range of spatial resolutions.
At the regional levels, the latitudinal and longitudinal diversity gradients had region-specific links to different environmental variables. Temperature seasonality exhibited a negative correlation with species diversity and outperformed AET in the Americas and the Africa-Europe region, but not in Asia-Oceania.Historical temperature change since the Last Glacial Maximum contributed substantially to shaping the latitudinal diversity gradient in the Americas, but not in the Asia-Oceania region. Older historical imprints (e.g., those of the Paleo- and Neogene) might have played a pivotal role in shaping the high species richness in the subtropical zone in East Asia.