Tracing the impact of the Andean uplift on Neotropical plant evolution.

Abstract

Recent phylogenetic studies have revealed the major role played by the uplift of the Andes in the extraordinary diversification of the Neotropical flora. These studies, however, have typically considered the Andean uplift as a single, time-limited event fostering the evolution of highland elements. This contrasts with geological reconstructions indicating that the uplift occurred in discrete periods from west to east and that it affected different regions at different times. We introduce an approach for integrating Andean tectonics with biogeographic reconstructions of Neotropical plants, using the coffee family (Rubiaceae) as a model group. The distribution of this family spans highland and montane habitats as well as tropical lowlands of Central and South America, thus offering a unique opportunity to study the influence of the Andean uplift on the entire Neotropical flora. Our results suggest that the Rubiaceae originated in the Paleotropics and used the boreotropical connection to reach South America. The biogeographic patterns found corroborate the existence of a long-lasting dispersal barrier between the Northern and Central Andes, the "Western Andean Portal." The uplift of the Eastern Cordillera ended this barrier, allowing dispersal of boreotropical lineages to the South, but gave rise to a huge wetland system ("Lake Pebas") in western Amazonia that prevented in situ speciation and floristic dispersal between the Andes and Amazonia for at least 6 million years. Here, we provide evidence of these events in plants.