PRJNA535438
Recent and local megadiversification of tropical rain forests in Central America
Central America links together the Americas and is a mosaic of mountain ranges, lowland fields and large lakes. This heterogeneous topography was formed from north to south during the Cenozoic and is largely covered by megadiverse tropical rain forests (TRFs). Unlike other species-rich American regions, Central American TRFs remain largely understudied. It is not clear whether they represent an ancient ecosystem or were assembled recently, and whether most species derive from neighboring regions or have evolved locally. To address these questions, we reconstructed the evolutionary history of a major component of TRFs, the palms (Arecaceae). We sampled species from across the Americas, with a focus on Central America for which we were able to obtain the majority of described species. We generated over 50,000 DNA nucleotides using Next Generation Sequencing methods, which we used to estimate dated phylogenetic relationships, and infer geographical range evolution. Our robust phylogeny shows unprecedented resolution at the species level in palms, and reveals that extant Central American palm diversity only started assembling in the last 12-8 Ma, with a burst in speciation around 4-2 Ma. These results suggest that extant TRFs of Central America are young, in striking contrast to the old assembly of TRFs in neighboring South America since at least 58 Ma. Although Central America is an important biotic corridor, dispersal contributed only at early stages of the assembly process and megadiversity is mostly explained by local diversification. These results showcase the potential of phylogenomic approaches to infer the evolution of entire biotas.