Phylogenetics and Evolutionary Biomechanics of Coral Reef Fishes

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Fishes of the family Labridae are a diverse group of nearly 600 species that inhabit tropical and temperate marine waters throughout the world and constitute a major segment of the diversity found on coral reefs. Advances in our understanding of the labrid family tree and study of the biomechanics of feeding behavior will allow exploration of evolution in coral reef fishes. The first goal of this project is to collect new DNA sequence data for several species groups within the Labridae. With previous NSF support, a family tree for the Labridae was generated using data for 115 species. Resolution of phylogenetic relationships on this tree was excellent based on four genes from different parts of the cell (2 each from the mitochondrion and the nucleus). However several large species groups remain unresolved. In this project, sequences of genes that are appropriate for species-level questions will be obtained for 120 additional taxa. In addition, this project will investigate two genes involved in early growth and development of fish skulls. These include Otx1, a gene that plays a role in head growth and Dlx2, a gene involved in both lower jaw formation and tooth development. Sequences for these genes will be collected in 50 species, having diverse skull structures and jaw anatomy. Thus, this study will provide new information from many species and many genes, some of which have known regulatory involvement in building a key part of the animal, the skull. The second objective of the proposal is to combine evolutionary trees with concepts from engineering design and knowledge of feeding behavior to study skull function. Specific hypotheses of evolutionary convergence will be tested to determine whether the same engineering solution has been achieved multiple times in the history of the group. The extreme modifications of jaws and skull found in this family make them a model system for evolution in cranial structure and function. Biomechanical engineering models allow calculation of basic feeding mechanics such as jaw closing force and speed, and jaw protrusion. Biomechanical models, generated as physical constructs and computer models, are useful for research and education. Combining evolution with function in many species, this project will examine evolutionary change in the biomechanics of one of the most diverse radiations of vertebrates on Earth. The movement toward an integrated understanding of biological structure and function, from genes to tissues to whole organisms, is one of the major frontiers of biology. This project contributes to that goal by testing specific hypotheses of functional evolution using molecular phylogenies and engineering concepts. This project contributes to education, training, exhibits, and research infrastructure in many ways. The Principal Investigator teaches undergraduate courses at the University of Chicago and lab exercises are held each year in the collections of the Field Museum. Students at the college, graduate, and postdoctoral levels are involved with all aspects of the proposed research, including sequencing, analysis, and biomechanics. Collaborations are underway with people from Austria, Australia, Chile, Kenya, Madagascar, New Zealand, The Philippines, and Thailand. Museum exhibits are now on display that feature models of fish head function developed from NSF-funded research, and exhibits are planned to feature both phylogenetic and functional research at the Field Museum. The PI gives museum lectures, has spoken on public radio, visits local schools, and presents coral reef fish biology to groups such as Elder Hostel and Rotary in the Chicago area. Physical and computer models of animal function featured in this proposal are fantastic tools for classroom education, research training, and museum exhibits.