Chapter 12 - The Speciation of South American and African Birds in Montane Regions

Abstract

The chapter examines macroscale patterns of avian species richness and relates this to macroscale patterns of diversification in tropical forests. It investigates where recent speciation has been most intensive and where old lineages (which show only phyletic speciation) predominate. The analysis provides evidence for bursts of speciation in montane regions during the Quaternary climatic–vegetational fluctuations and does not support the hypothesis that avian diversification was intensive in the lowland regions during this period. As montane regions are highly heterogeneous with regard to vegetation, climate, and topography, there is a good chance that areas of paleoecological stability may exist as small pockets within them. The case studies described here illustrate some aspects of the biogeographic dynamics that must be considered in order to understand the processes involved in the evolution of the rich avifauna of tropical forests. It is evident that a great deal of avian diversity has been generated in recent times within tropical montane regions and that further studies are needed to understand its magnitude. In particular, the prediction in the model hypothesis that lowland rainforest biota are recruited from radiations in montane regions needs to be fully tested using phylogenetic studies.