Dissertation Research: Developmental Bases of Anolis Limb Evolution

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Dissertation Research: The Developmental Bases of Anolis Limb EvolutionJeremy J. Gibson-Brown and Thomas J. SangerWashington University in Saint Louis In the past twenty years, advances in understanding of how developmental processes change over macroevolutionary time scales have greatly improved knowledge about the mechanisms and processes responsible for generating the world's biological diversity. Complementing the macroevolutionary approach with research focusing on historical and mechanistic studies, both within and between closely related species, will greatly enhance understanding of the processes underlying morphological evolution. Recent analytical and technical advances in the fields of evolutionary and developmental biology make this the perfect time to integrate these disciplines and to investigate the microevolutionary processes underlying morphologic change. Of particular interest are the relationships between developmental variability and evolutionary divergence. This relationship is important because a bias in the production of developmental variation could be viewed as facilitating or constraining evolutionary change, depending on the relationship between selection, and dimensions of greater or lesser variation, respectively. For their research Dr. Gibson-Brown and his student, Thomas Sanger, will take advantage of the well-studied ecomorphs of Anolis lizards on each island of the Greater Antilles: Cuba, Hispaniola, Jamaica, and Puerto Rico. They propose to study how developmental mechanisms have changed during the convergent evolution of lizard limb morphologies at multiple levels of the biological hierarchy (morphological, cellular, and molecular). They will specifically test the hypothesis that different species have evolved similar limb lengths using the same developmental mechanisms. To test this hypothesis their study is divided into three specific aims. They will first compare the relative growth of long-limbed and short-limbed species on each island to establish the time during development that limb length differences are determined. Using this information they will then examine the cellular mechanisms of bone growth at these times to compare the developmental mechanisms by which growth rates are changing. Finally, they will begin to identify the molecular mechanisms leading to differences in growth between species by examining genes thought to be differentially expressed in the growth plates. This will also be the first study to examine reptilian bone growth in over thirty years. This research has several broader impacts beyond the scope of this project. Dr. Gibson-Brown and Mr. Sanger actively support the participation of underrepresented minorities in this research project, including students and teachers. They incorporate several undergraduate research assistants each semester, some of whom conduct their own related research projects. Their work has also fostered collaborations between several biological disciplines and universities.