Dissertation Research: Historical Biogeography and Molecular Phylogenetics of Chamaeleonidae

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0073323Larson and Townsend The distribution of animal and plant species over the earth has long puzzled biologists, as it often appears that closely related species are found in geographically separated areas while intervening regions are devoid of members of the same group. With the advent of plate tectonic theory, new ideas about species distributions based on continental drift could be formulated, and these hypotheses could ideally be tested if a reliably supported phylogeny (evolutionary genealogy) of the group in question were available. With the modern tools of DNA sequencing now available to systematists, well supported phylogenies can be obtained for numerous groups of animals and plants, providing opportunities to test proposed patterns of distribution resulting from plate tectonic events. The primary goal of work by graduate student Ted Townsend, with guidance from faculty adviser Allan Larson, is to construct a phylogenetic hypothesis for the lizard family Chamaeleonidae using DNA sequence data, and then to use this phylogeny to test various biogeographic hypotheses about the group. Chamaeleons include about 130 species of easily recognizable lizards, distributed in Africa, Madagascar, and India, with a few species ranging into southernmost Europe. The first three landmasses are remnants of the southern supercontinent of Gondwana which, according to plate tectonic theory, began its breakup about 140 million years ago. A reliable phylogeny of chamaeleons would allow tests of historical patterns of migration and of lineage splitting, which has so far not been possible on the basis of morphological studies of traditional taxonomic characters. New evidence from mitochondrial gene sequences and from two potential nuclear genes will help construct a phylogenetic framework for the group, based on field collected materials from Africa and Madagascar and from samples provided by colleagues and museum holdings.