Avian Diversification in the Andes: Understanding Endemism Patterns and Historical Biogeography
The Andes, along with the Amazon and Atlantic forests, harbor the richest avifauna in the world with roughly one third of all the world's species of birds. Many biogeographical studies have sought to explain the origin and diversification of Andean taxa. However, because of the Andes' extensive latitudinal span and complexity, there is no one single cause of origin or of diversification that can explain the diversity found in them. Along the Andes, multiple biogeographic patterns of disjunction between highland and lowland sister-groups have been linked to Andean uplift. For example, Ribas et al. (2007) provided evidence that the spatio-temporal diversification in the monophyletic parrot genus Pionus is causally linked to Andean tectonic and palaeoclimate change through vicariance. Thus, if the Andes uplift is responsible for some of the patterns of montane-lowland disjunctions, it may be one of the mechanisms underlying the taxonomic assembly of the Andean montane avifauna. In this dissertation I explored whether the origin and diversification of three groups of Andean birds--the exclusively Andean parrot genera Hapalopsittaca, the subclade of mangoes containing Doryfera, Schistes, and Colibri, and the ovenbirds of the tribe Thripophagini--can be linked to Earth history. The results show that the origin of these Andean taxa can be explained through vicariance from their lowland sister-groups, mediated by the uplift of the Andes. Thus, this thesis proposes that geological events are directly responsible for originating diversity throughout montane environments. Once in the Andes, the diversification of these montane taxa can be explained by events such as the tectonic evolution of the Andes--which created canyons and valleys that may have caused the vicariance of continuous populations--as well as by the climatic oscillation of the Pleistocene, which caused altitudinal shifts, expansion, and contraction of the montane vegetation belts during the climatic oscillations of the Pleistocene. In summary a significant part of the temporal patterns of origins and diversification of the three groups of birds included in this study can be linked to Earth history, both in terms of the tectonic history of the Andes and of the climatic events of the Pleistocene.
Evolution (Biology), Birds--Evolution, Biodiversity, Parrots, Biology, Zoology
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