The humid forests that cover the tropical mountains of South America sustain one of the highest diversity of bird species in the world. This huge avifauna is packed in different elevation zones and stretches along the narrow strip of cloud forest of the Andes, from Bolivia to Venezuela. The geographic distributions of the birds from this habitat are fragmented by low-elevation dry valleys, which function as barriers to interbreeding between populations. The isolation imposed by these valleys has the potential to promote the genetic and phenotypic divergence of bird populations, and may ultimately result in the formation of new species. This diversification could have been intensified during the forest movements up and down the mountain slopes that resulted from climatic changes in the glacial age. For example, in the coldest periods of the glaciations, montane forests moved downslope several hundred meters bridging the gap across valley barriers and facilitating the contact of formerly isolated populations. These ideas are addressed by means of a large-scale comparative analysis of the genetics of population divergence. Approximately 250 species of birds will be studied in the slopes of two large valleys in the Andes. Five species will be the subjects of a more intensive genetic analysis to infer historical factors associated with habitat movements.

This investigation not only will provide new insights into the mechanisms driving diversification, but also will increase our knowledge of biodiversity for its conservation. Furthermore it will enhance training in biology to undergraduate female students in Colombia and Venezuela. The graduate student is mentoring two student theses and has made presentations to university and national park staff.

National Science Foundation (NSF)
Division of Integrative Organismal Systems (IOS)
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David Stephens
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Louisiana State University & Agricultural and Mechanical College
Baton Rouge
United States
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