9623426 TUCKER The primary goal of studies in systematic biology is to understand the processes that give rise to the diversity of life. Reconstructing the historical (OphylogeneticO) relationships among organisms is the first step in studying the patterns of diversity and elucidating the processes that give rise to this diversity. This project investigates the phylogenetic relationships among an exceptionally diverse group of mammals, the native rodents of Madagascar (the nesomyine rodents; subfamily Nesomyinae), and explores the relationships among these rodents and rodents native to mainland Africa. The seven genera and 14 species of Nesomyinae are exceedingly diverse morphologically and ecologically; the only "character" serving to unite the group is their common distribution on Madagascar. There is some uncertainty whether the nesomyines are a result of a single adaptive radiation or of multiple migrations to the island. If the nesomyine rodents are in fact the result of one migration event, it is certainly one of the most spectacular mammalian radiations on earth. An organism's phylogenetic history is written in its DNA. This study, by Sharon Jansa under the direction of Priscilla Tucker, therefore will use DNA sequence data to uncover the relationships among nesomyine rodents. Data will be obtained from two genes: the maternally inherited cytochrome b gene and the biparentally inherited zona pellucida 3 gene. The combination of maternally inherited and biparentally inherited gene sequence data is likely to accurately reflect the history of the organisms and not simply the history of the genes. This study is significant in that it is the first to use a molecular data set to investigate the phylogeny of the nesomyine rodents. The knowledge of relationships obtained from this study will provide a framework for examining the ecological and morphological specializations among this diverse group of mammals. This may be the only opportunity to study this unique fauna, whi ch is rapidly disappearing due to continuing deforestation and encroachment of human-introduced species.
