Pantropical diversification of padauk trees and relatives was influenced by biome‐switching and long‐distance dispersal

Aim Phenotypes promoting dispersal over ecological timescales may have macroevolutionary consequences, such as long-distance dispersal and diversification. However, whether dispersal traits explain the distribution of pantropical plant groups remains unclear. Here we reconstruct the biogeographical history of a tree clade to assess whether seed dispersal traits and biome-switching explain the clade's pantropical distribution. Location Pantropical. Taxon The Pterocarpus clade (Leguminosae/Fabaceae). Methods We sequenced 303 nuclear loci using target capture and generated a time-calibrated phylogenomic tree. We also generated a corroborative time-calibrated phylogenetic tree from data-mined Sanger-sequencing data. We then collated distribution data and seed dispersal morphology traits to compare trait-dependent and trait-independent biogeographical models, allowing us to infer whether dispersal traits influenced Pterocarpus' spatio-temporal evolution. Finally, using the results of these model tests, we estimated the ancestral ranges and biomes of Pterocarpus species to better understand their biogeographical history, and assessed the degree and direction of biome-switching over the course of their diversification. Results We recovered well-supported phylogenetic relationships within Pterocarpus, within which there were two subclades - one neotropical and the other palaeotropical. Our divergence date estimates suggested that Pterocarpus diversified from around 12 Ma, during the Miocene. Trait-dependent biogeographical models were rejected for both range and biome evolution within Pterocarpus, but models including dispersal were supported. Pterocarpus' ancestral node shared a range across the new-world and old-world tropics, followed by divergence into palaeotropical and neotropical clades. Biome-switching occurred most frequently into rainforest and grassland. Main conclusions Our analyses suggest that Pterocarpus underwent infrequent cross-continental dispersal and establishment into novel biomes. While this was minimally impacted by seed dispersal traits, biome-switching following long-distance dispersal and climate change have played an important role in diversification within Pterocarpus since the Miocene. Indeed, rare events of long-distance dispersal likely explain the wide distributions of many pantropical plant species.