|Year of Publication:
|A. Antonelli, Quijada-Mascareñas, A., Crawford, A. J., Bates, J. M., Velazco, P. M., Wüster, W.
|In Hoorn, C., Wesselingh, F.: Amazonia, Landscape and Species Evolution, 1st edition. Blackwell publishing
Explaining the origins and evolution of Amazonian biodiversity continues to be an outstanding question in evolutionary biology. A plethora of mechanisms for promoting diversification has been proposed, generally invoking ecological and vicariance processes associated with major geological, hydrological and climatic events in the history of the Amazon drainage basin. Here, we review recent advances on this topic in the light of a rich new source of information: molecular phylogenetics and especially phylogeography. We present a comparison of phylogeographical studies covering over 50 clades of amphibians, birds, non-avian reptiles and mammals, focusing on studies where estimates of divergence times were explicitly calculated. We then discuss the congruence of the speciation patterns found in these studies with previous hypotheses of diversification. Based on the estimates of crown group ages, we conclude that a high proportion of present-day diversity is a result of Neogene diversification. The origin of most species clearly predates the Pleistocene by a considerable margin, refuting the long-held hypothesis that repeated expansion and contraction of lowland forests during Pleistocene climatic changes would be responsible for most of the Amazonian biodiversity. However, some evidence from phylogenetic and distributional patterns suggests that climate cycles did trigger speciation. Speciose lineages of tetrapods tend to be older than groups containing one to a few species, with a few notable exceptions. Considering each tetrapod group alone, amphibians and non-avian reptiles are generally older than birds, while mammals contain both recent and ancient clades of approximately the same number of species. Finally, we make recommendations about future research approaches and animal systems that deserve further attention from phylogeographers.