Abstract
Hundreds of millions of Euros are spent on the protection of biodiversity hotspots in tropical rainforests. Strangely, there is no agreement on the factors responsible for these hotspots. Explanations have long been sought in contemporary environmental factors. However, these factors are inadequate to account for the patterns found. The role of regional history, biogeographical barriers and processes such as extinction are more important to explain observed patterns than previously thought. Support has been obtained for the ?"historic climate stability? hypothesis" (species-richness is highest in areas where climate has not changed for long geological periods), but large scale corroboration is still scarce. Here, a novel approach is taken, combining contemporary and historical aspects, to investigate factors contributing to speciation. Also, the ?"historic climate stability? hypothesis" is tested. In order to do so, a species-level phylogeny (tree-shaped representation of evolutionary history) of a group of tropical trees is reconstructed using 454-sequencing. Phylogenies enable testing of hypotheses at geographic- and time-scales where manipulative experiments are impossible. 454-sequeuncing enables high-throughput data collection, unattainable with traditional methods. With Species Distribution Modelling (ancestral) species distributions are generated. By comparing distributions of closely related species, the mode of speciation is inferred. Moreover, species ranges are compared between groups in lowland West Amazonia and other regions, expecting narrower ranges in the former as predicted by the ?historic climate stability? hypothesis. Lastly, differences in speciation rates are examined among rainforest regions with different ecological, geological and/or climatic histories thus identifying factors promoting speciation. This approach is innovative because phylogenetic and distributional data have not been combined in a single study of this scale. Furthermore, this is the first use of 454-sequencing in a large-scale species-level phylogenetic project and therefore is a "proof of concept" study. The reconstructed phylogeny will be highly instructive for unravelling the causes of Neotropical diversity.
Netherlands