Testing White’s Floristic Impoverishment Hypothesis in the Forest-Savanna Transition Zones of Africa

In tropical Africa, forests and savannas are the two most widespread biomes potentially represent alternative stable states with a divergent species composition. A classic, but untested, hypothesis posited by White (1983) suggests that transition zones between contain floristically impoverished assemblage, few representatives from each biome. Further, evolutionary dimension of diversity has received limited attention, despite its importance for understanding biogeographic history biomes. Here, we quantified richness several measures in 1° grid cells, using c. 300,000 occurrence records trees shrubs combined biome affiliation data 3203 species. We found assemblages hold fewer woody than forest savanna zones, as White. However, more phylogenetic expected given their richness, whether one considers separately or together. also show Congo Basin low levels diversity, number species, highlight south-eastern African centre diversity. Regions high both were centred around Dahomey Gap Cameroon, mainly zones. Overall, our study shows even if impoverished, unexpectedly This they important centres innovation diversification and/or serve crossroads, where lineages diversified contrasting environments coexist within single area.