Iriarteeae palms tracked the uplift of Andean Cordilleras

Aim: The high biodiversity of northern South America is unparalleled and includesseveral centres of diversity such as Amazonia, the Andes and the Choco. Movementof lineages amongst and within these bioregions is thought to be rare, and theeffect of those dispersals on the distribution, diversity, and community assemblyremains poorly understood. Here we address these effects by studying divergencetimes, biogeographical history, and species diversification of the palm tribe Iriar-teeae, an ecologically dominant forest component.

Location: Central and South America.

Methods: We developed a calibrated phylogeny and a spatially explicit diversifica-tion model that incorporates molecular and fossil data. In these analyses, weincluded a new fossil Iriartea species Gemmamonocolpites galeanoana, derived fromnew samples of Miocene deposits in western Amazonia. We also estimated the geo-graphical range evolution of lineages and tested whether speciation and extinctionrates were affected by dispersal events using a simulation approach in ClaSSE.

Results: Dispersal amongst bioregions was not evenly distributed across the topol-ogy. We found that Amazonian communities are overdispersed across the phy-logeny, whereas Andean taxa are clustered. Dispersal events were associated withincreases in species diversification and were concomitant with periods of Andeanuplift. Migration into montane areas occurred several times from lowland Amazonianancestors, and montane taxa subsequently recolonized the Amazonian bioregion.

Main conclusions: Our results suggest that the diversification of Iriarteeae palmsclosely followed the west-to-east surface uplift history of the Northern Andes. Froman early, lowland Amazonian ancestor, the first diversification events took place inthe earliest emerging mountain chain, the Western Cordillera. From there multiplerange expansions followed eastwards and back into the lowlands. This study demon-strates how geological events within a single mountain range can affect the geo-graphical expansion and diversification of lineages.