Climatic preferences of major plant clades define the functional attributes of African savanna types

Forecasting how the Earth system will respond to global change includes simplifying the functional diversity induced by thousands of plant species into tractable units. The dominant strategy has been to aggregate species into plant functional types (PFTs), assuming that selection leads to unrelated species converging to similar ecological roles. An alternative would be to harness niche conservatism, the tendency of lineages to retain ancestral ecological traits, and assume that phylogenetically related species tend to have similar ecological roles. Using African savannas as case study, we use phylogenetically defined groups to identify phytoclimes: climate-defined regions that support distinct sets of plant types. We found that taxonomically-based phytoclimes aligned with a respected expert map of Africa. Moreover, this scheme could be reconciled with existing conceptual models used to describe the functional diversity of savannas. This alignment of phylogenetic and functional interpretations suggests that African savannas are dominated by a limited set of pre-adapted taxa, rather than arising through widespread convergence. Our findings suggest that phylogenetic information can provide a parsimonious, functional basis for representing ecosystem diversity in global change models. Harnessing this alignment between phylogenetic and functional groupings offers a promising route for improving the predictive ability of Earth system models.