Resumen:
Aim: The high biodiversity of northern South America is unparalleled and includes
several centres of diversity such as Amazonia, the Andes and the Choc o. Movement
of lineages amongst and within these bioregions is thought to be rare, and the
effect of those dispersals on the distribution, diversity, and community assembly
remains poorly understood. Here we address these effects by studying divergence
times, biogeographical history, and species diversification of the palm tribe Iriarteeae,
an ecologically dominant forest component.
Location: Central and South America.
Methods: We developed a calibrated phylogeny and a spatially explicit diversification
model that incorporates molecular and fossil data. In these analyses, we
included a new fossil Iriartea species Gemmamonocolpites galeanoana, derived from
new samples of Miocene deposits in western Amazonia. We also estimated the geographical
range evolution of lineages and tested whether speciation and extinction
rates were affected by dispersal events using a simulation approach in ClaSSE.
Results: Dispersal amongst bioregions was not evenly distributed across the topology.
We found that Amazonian communities are overdispersed across the phylogeny,
whereas Andean taxa are clustered. Dispersal events were associated with
increases in species diversification and were concomitant with periods of Andean
uplift. Migration into montane areas occurred several times from lowland Amazonian
ancestors, and montane taxa subsequently recolonized the Amazonian bioregion.
Main conclusions: Our results suggest that the diversification of Iriarteeae palms
closely followed the west-to-east surface uplift history of the Northern Andes. From
an early, lowland Amazonian ancestor, the first diversification events took place in
the earliest emerging mountain chain, the Western Cordillera. From there multiple
range expansions followed eastwards and back into the lowlands. This study demonstrates
how geological events within a single mountain range can affect the geographical
expansion and diversification of lineages.