Two central themes pervade many questions relating to the origin of patterns in biological diversity: (1) How do patterns of diversity in adaptation (for example, feeding specializations) evolve within evolutionary lineages? and (2) How are patterns in the geographic distributions of organisms generated through the interaction of biological and geological (for example, continental drift processes? Hypotheses of evolutionary relationships (phylogeny) among members of a lineage are the foundation upon which answers to such questions are based. The proposed research will establish a detailed phylogeny for three lineages of Central and South American snakes selected for their morphological and ecological diversity. These will be used to address questions concerning patterns of evolution of that diversity and will provide a historical framework for interpreting their distributions. The lineages to be studied include the only snakes to have colonized the Galapagos Islands, which have been considered a classic "natural experiment " for the study of evolutionary processes. Field work associated with the project will proved ecological information on the included species, specimens for morphological studies, and tissues for subsequent biochemical analyses. Relationships among snakes will be evaluated using morphological characters and biochemical characters of proteins (enzymes) and nucleic acids (DNA). The phylogenies developed for these lineages will be directly applicable to questions concerning the evolutionary biology of these snakes. More generally, however, there will be significance in addressing questions concerning evolutionary processes that generate diversity in morphology, and historical hypotheses concerning the distributional history (biogeography) of the Central and South American fauna.
