Phylogenetic relationships and biogeographical patterns in Combretaceae and the role of drift fruits in their pantropical distribution

The evolutionary history of Combretaceae includes multiple inter-continental migrations and biome shifts. Seed dispersal traits may have been critical to migrations and biome shifts, but previous evaluation is lacking. Our understanding of relationships within genera remains poor, particularly in the largest genera Combretum and Terminalia. Phylogenomics and target capture are powerful tools providing new evolutionary insights. We built a robust dated phylogenetic tree of Combretaceae based on a target capture approach using the Angiosperms353 kit. We combined phylogenetic data with seed dispersal traits, biome data and biogeographic ranges to reconstruct biogeographical history. Ancestral range reconstruction suggests a Gondwanan origin (Africa/ South America), consistent with previous analyses, with several inter-continental dispersals within the family and fewer transitions between biomes. Relative abundance of fruit dispersal types differed by both continent and biome. However, inter-continental colonisations were only significantly enhanced by water dispersal (drift fruit), and there was no evidence that seed dispersal influenced biome shifts. Our analysis provides evidence for the potential of drift-fruit to disperse Combretaceae. Dispersal mode did not influence biome shifts. This suggests a paradox on the acquisition of new dispersal traits, which can explain distribution and habitat preferences of pan-tropical plant clades.